[PATCH v3 0/5] powernv: Enable Dynamic Frequency

From: "Gautham R. Shenoy" <redacted>

Hi,

This is the v3 of the consolidated patchset consisting
patches for enabling cpufreq on IBM POWERNV platforms
along with some enhancements. I have incorporated the review 
for v2 (which can be found at [1]).

- This patchset contains code for the platform driver to support CPU
  frequency scaling on IBM POWERNV platforms.

- In addition to the standard control and status files exposed by the
  cpufreq core, the patchset exposes the nominal frequency through the
  file named "cpuinfo_nominal_freq".


The changes from from v2:
  - Updated the changelog for "powernv: cpufreq driver for powernv platform"
    to record the fact that policy->cpus must be populated with a sibling mask
    that includes even the offlined siblings.

  - Dropped the patch named 
    "powernv:cpufreq: Create a powernv_cpu_to_core_mask() helper"
     since the driver->get() method can use cpu_sibling_mask().
  
  -  Updated "powernv:cpufreq: Implement the driver->get() method" to 
     use cpu_sibling_mask() in powernv_cpufreq_get()

The patchset is based against commit 4907cdca7210c5895311bddcf05a4c85b67d8566
of the mainline tree.

[1]: https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-March/115861.html


Gautham R. Shenoy (3):
  powernv:cpufreq: Create pstate_id_to_freq() helper
  powernv:cpufreq: Export nominal frequency via sysfs.
  powernv:cpufreq: Implement the driver->get() method

Srivatsa S. Bhat (1):
  powernv,cpufreq:Add per-core locking to serialize frequency
    transitions

Vaidyanathan Srinivasan (1):
  powernv: cpufreq driver for powernv platform

 arch/powerpc/include/asm/reg.h         |   4 +
 arch/powerpc/platforms/powernv/Kconfig |   1 +
 drivers/cpufreq/Kconfig                |   1 +
 drivers/cpufreq/Kconfig.powerpc        |  13 ++
 drivers/cpufreq/Makefile               |   1 +
 drivers/cpufreq/powernv-cpufreq.c      | 375 +++++++++++++++++++++++++++++++++
 6 files changed, 395 insertions(+)
 create mode 100644 drivers/cpufreq/powernv-cpufreq.c

-- 
1.8.3.1

From: Vaidyanathan Srinivasan <redacted>

Backend driver to dynamically set voltage and frequency on
IBM POWER non-virtualized platforms.  Power management SPRs
are used to set the required PState.

This driver works in conjunction with cpufreq governors
like 'ondemand' to provide a demand based frequency and
voltage setting on IBM POWER non-virtualized platforms.

PState table is obtained from OPAL v3 firmware through device
tree.

powernv_cpufreq back-end driver would parse the relevant device-tree
nodes and initialise the cpufreq subsystem on powernv platform.

The policy->cpus needs to be populated in a hotplug-invariant manner
instead of using cpu_sibling_mask() which varies with cpu-hotplug. This
is because the cpufreq core code copies this content into policy->related_cpus
mask which is should not vary on cpu-hotplug.

[Change log updated by ego@linux.vnet.ibm.com]

Signed-off-by: Vaidyanathan Srinivasan <redacted>
Signed-off-by: Srivatsa S. Bhat <redacted>
Signed-off-by: Anton Blanchard <redacted>
Signed-off-by: Gautham R. Shenoy <redacted>
---
 arch/powerpc/include/asm/reg.h         |   4 +
 arch/powerpc/platforms/powernv/Kconfig |   1 +
 drivers/cpufreq/Kconfig                |   1 +
 drivers/cpufreq/Kconfig.powerpc        |  13 ++
 drivers/cpufreq/Makefile               |   1 +
 drivers/cpufreq/powernv-cpufreq.c      | 277 +++++++++++++++++++++++++++++++++
 6 files changed, 297 insertions(+)
 create mode 100644 drivers/cpufreq/powernv-cpufreq.c

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 90c06ec..84f92ca 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h

@@ -271,6 +271,10 @@
 #define SPRN_HSRR1	0x13B	/* Hypervisor Save/Restore 1 */
 #define SPRN_IC		0x350	/* Virtual Instruction Count */
 #define SPRN_VTB	0x351	/* Virtual Time Base */
+#define SPRN_PMICR	0x354   /* Power Management Idle Control Reg */
+#define SPRN_PMSR	0x355   /* Power Management Status Reg */
+#define SPRN_PMCR	0x374	/* Power Management Control Register */
+
 /* HFSCR and FSCR bit numbers are the same */
 #define FSCR_TAR_LG	8	/* Enable Target Address Register */
 #define FSCR_EBB_LG	7	/* Enable Event Based Branching */

diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig
index 895e8a2..1fe12b1 100644
--- a/arch/powerpc/platforms/powernv/Kconfig
+++ b/arch/powerpc/platforms/powernv/Kconfig

@@ -11,6 +11,7 @@ config PPC_POWERNV
 	select PPC_UDBG_16550
 	select PPC_SCOM
 	select ARCH_RANDOM
+	select CPU_FREQ
 	default y
 
 config PPC_POWERNV_RTAS

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 4b029c0..4ba1632 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig

@@ -48,6 +48,7 @@ config CPU_FREQ_STAT_DETAILS
 choice
 	prompt "Default CPUFreq governor"
 	default CPU_FREQ_DEFAULT_GOV_USERSPACE if ARM_SA1100_CPUFREQ || ARM_SA1110_CPUFREQ
+	default CPU_FREQ_DEFAULT_GOV_ONDEMAND if POWERNV_CPUFREQ
 	default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
 	help
 	  This option sets which CPUFreq governor shall be loaded at

diff --git a/drivers/cpufreq/Kconfig.powerpc b/drivers/cpufreq/Kconfig.powerpc
index ca0021a..93f8689 100644
--- a/drivers/cpufreq/Kconfig.powerpc
+++ b/drivers/cpufreq/Kconfig.powerpc

@@ -54,3 +54,16 @@ config PPC_PASEMI_CPUFREQ
 	help
 	  This adds the support for frequency switching on PA Semi
 	  PWRficient processors.
+
+config POWERNV_CPUFREQ
+       tristate "CPU frequency scaling for IBM POWERNV platform"
+       depends on PPC_POWERNV
+       select CPU_FREQ_GOV_PERFORMANCE
+       select CPU_FREQ_GOV_POWERSAVE
+       select CPU_FREQ_GOV_USERSPACE
+       select CPU_FREQ_GOV_ONDEMAND
+       select CPU_FREQ_GOV_CONSERVATIVE
+       default y
+       help
+	 This adds support for CPU frequency switching on IBM POWERNV
+	 platform

diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 7494565..0dbb963 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile

@@ -86,6 +86,7 @@ obj-$(CONFIG_PPC_CORENET_CPUFREQ)   += ppc-corenet-cpufreq.o
 obj-$(CONFIG_CPU_FREQ_PMAC)		+= pmac32-cpufreq.o
 obj-$(CONFIG_CPU_FREQ_PMAC64)		+= pmac64-cpufreq.o
 obj-$(CONFIG_PPC_PASEMI_CPUFREQ)	+= pasemi-cpufreq.o
+obj-$(CONFIG_POWERNV_CPUFREQ)		+= powernv-cpufreq.o
 
 ##################################################################################
 # Other platform drivers

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
new file mode 100644
index 0000000..ab1551f
--- /dev/null
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -0,0 +1,277 @@
+/*
+ * POWERNV cpufreq driver for the IBM POWER processors
+ *
+ * (C) Copyright IBM 2014
+ *
+ * Author: Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#define pr_fmt(fmt)	"powernv-cpufreq: " fmt
+
+#include <linux/module.h>
+#include <linux/cpufreq.h>
+#include <linux/of.h>
+#include <asm/cputhreads.h>
+
+/* FIXME: Make this per-core */
+static DEFINE_MUTEX(freq_switch_mutex);
+
+#define POWERNV_MAX_PSTATES	256
+
+static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
+static int powernv_pstate_ids[POWERNV_MAX_PSTATES+1];
+
+/*
+ * Initialize the freq table based on data obtained
+ * from the firmware passed via device-tree
+ */
+
+static int init_powernv_pstates(void)
+{
+	struct device_node *power_mgt;
+	int nr_pstates = 0;
+	int pstate_min, pstate_max, pstate_nominal;
+	const __be32 *pstate_ids, *pstate_freqs;
+	int i;
+	u32 len_ids, len_freqs;
+
+	power_mgt = of_find_node_by_path("/ibm,opal/power-mgt");
+	if (!power_mgt) {
+		pr_warn("power-mgt node not found\n");
+		return -ENODEV;
+	}
+
+	if (of_property_read_u32(power_mgt, "ibm,pstate-min", &pstate_min)) {
+		pr_warn("ibm,pstate-min node not found\n");
+		return -ENODEV;
+	}
+
+	if (of_property_read_u32(power_mgt, "ibm,pstate-max", &pstate_max)) {
+		pr_warn("ibm,pstate-max node not found\n");
+		return -ENODEV;
+	}
+
+	if (of_property_read_u32(power_mgt, "ibm,pstate-nominal",
+				 &pstate_nominal)) {
+		pr_warn("ibm,pstate-nominal not found\n");
+		return -ENODEV;
+	}
+	pr_info("cpufreq pstate min %d nominal %d max %d\n", pstate_min,
+		pstate_nominal, pstate_max);
+
+	pstate_ids = of_get_property(power_mgt, "ibm,pstate-ids", &len_ids);
+	if (!pstate_ids) {
+		pr_warn("ibm,pstate-ids not found\n");
+		return -ENODEV;
+	}
+
+	pstate_freqs = of_get_property(power_mgt, "ibm,pstate-frequencies-mhz",
+				      &len_freqs);
+	if (!pstate_freqs) {
+		pr_warn("ibm,pstate-frequencies-mhz not found\n");
+		return -ENODEV;
+	}
+
+	WARN_ON(len_ids != len_freqs);
+	nr_pstates = min(len_ids, len_freqs) / sizeof(u32);
+	WARN_ON(!nr_pstates);
+
+	pr_debug("NR PStates %d\n", nr_pstates);
+	for (i = 0; i < nr_pstates; i++) {
+		u32 id = be32_to_cpu(pstate_ids[i]);
+		u32 freq = be32_to_cpu(pstate_freqs[i]);
+
+		pr_debug("PState id %d freq %d MHz\n", id, freq);
+		powernv_freqs[i].driver_data = i;
+		powernv_freqs[i].frequency = freq * 1000; /* kHz */
+		powernv_pstate_ids[i] = id;
+	}
+	/* End of list marker entry */
+	powernv_freqs[i].driver_data = 0;
+	powernv_freqs[i].frequency = CPUFREQ_TABLE_END;
+
+	/* Print frequency table */
+	for (i = 0; powernv_freqs[i].frequency != CPUFREQ_TABLE_END; i++)
+		pr_debug("%d: %d\n", i, powernv_freqs[i].frequency);
+
+	return 0;
+}
+
+static struct freq_attr *powernv_cpu_freq_attr[] = {
+	&cpufreq_freq_attr_scaling_available_freqs,
+	NULL,
+};
+
+/* Helper routines */
+
+/* Access helpers to power mgt SPR */
+
+static inline unsigned long get_pmspr(unsigned long sprn)
+{
+	switch (sprn) {
+	case SPRN_PMCR:
+		return mfspr(SPRN_PMCR);
+
+	case SPRN_PMICR:
+		return mfspr(SPRN_PMICR);
+
+	case SPRN_PMSR:
+		return mfspr(SPRN_PMSR);
+	}
+	BUG();
+}
+
+static inline void set_pmspr(unsigned long sprn, unsigned long val)
+{
+	switch (sprn) {
+	case SPRN_PMCR:
+		mtspr(SPRN_PMCR, val);
+		return;
+
+	case SPRN_PMICR:
+		mtspr(SPRN_PMICR, val);
+		return;
+
+	case SPRN_PMSR:
+		mtspr(SPRN_PMSR, val);
+		return;
+	}
+	BUG();
+}
+
+static void set_pstate(void *pstate)
+{
+	unsigned long val;
+	unsigned long pstate_ul = *(unsigned long *) pstate;
+
+	val = get_pmspr(SPRN_PMCR);
+	val = val & 0x0000ffffffffffffULL;
+	/* Set both global(bits 56..63) and local(bits 48..55) PStates */
+	val = val | (pstate_ul << 56) | (pstate_ul << 48);
+	pr_debug("Setting cpu %d pmcr to %016lX\n", smp_processor_id(), val);
+	set_pmspr(SPRN_PMCR, val);
+}
+
+static int powernv_set_freq(cpumask_var_t cpus, unsigned int new_index)
+{
+	unsigned long val = (unsigned long) powernv_pstate_ids[new_index];
+
+	/*
+	 * Use smp_call_function to send IPI and execute the
+	 * mtspr on target cpu.  We could do that without IPI
+	 * if current CPU is within policy->cpus (core)
+	 */
+
+	val = val & 0xFF;
+	smp_call_function_any(cpus, set_pstate, &val, 1);
+	return 0;
+}
+
+static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+	int base, i;
+
+#ifdef CONFIG_SMP
+	base = cpu_first_thread_sibling(policy->cpu);
+
+	for (i = 0; i < threads_per_core; i++)
+		cpumask_set_cpu(base + i, policy->cpus);
+#endif
+	policy->cpuinfo.transition_latency = 25000;
+
+	policy->cur = powernv_freqs[0].frequency;
+	cpufreq_frequency_table_get_attr(powernv_freqs, policy->cpu);
+	return cpufreq_frequency_table_cpuinfo(policy, powernv_freqs);
+}
+
+static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+	cpufreq_frequency_table_put_attr(policy->cpu);
+	return 0;
+}
+
+static int powernv_cpufreq_verify(struct cpufreq_policy *policy)
+{
+	return cpufreq_frequency_table_verify(policy, powernv_freqs);
+}
+
+static int powernv_cpufreq_target(struct cpufreq_policy *policy,
+			      unsigned int target_freq,
+			      unsigned int relation)
+{
+	int rc;
+	struct cpufreq_freqs freqs;
+	unsigned int new_index;
+
+	cpufreq_frequency_table_target(policy, powernv_freqs, target_freq,
+				       relation, &new_index);
+
+	freqs.old = policy->cur;
+	freqs.new = powernv_freqs[new_index].frequency;
+	freqs.cpu = policy->cpu;
+
+	mutex_lock(&freq_switch_mutex);
+	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
+
+	pr_debug("setting frequency for cpu %d to %d kHz index %d pstate %d",
+		 policy->cpu,
+		 powernv_freqs[new_index].frequency,
+		 new_index,
+		 powernv_pstate_ids[new_index]);
+
+	rc = powernv_set_freq(policy->cpus, new_index);
+
+	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
+	mutex_unlock(&freq_switch_mutex);
+
+	return rc;
+}
+
+static struct cpufreq_driver powernv_cpufreq_driver = {
+	.verify		= powernv_cpufreq_verify,
+	.target		= powernv_cpufreq_target,
+	.init		= powernv_cpufreq_cpu_init,
+	.exit		= powernv_cpufreq_cpu_exit,
+	.name		= "powernv-cpufreq",
+	.flags		= CPUFREQ_CONST_LOOPS,
+	.attr		= powernv_cpu_freq_attr,
+};
+
+static int __init powernv_cpufreq_init(void)
+{
+	int rc = 0;
+
+	/* Discover pstates from device tree and init */
+
+	rc = init_powernv_pstates();
+
+	if (rc) {
+		pr_info("powernv-cpufreq disabled\n");
+		return rc;
+	}
+
+	rc = cpufreq_register_driver(&powernv_cpufreq_driver);
+	return rc;
+}
+
+static void __exit powernv_cpufreq_exit(void)
+{
+	cpufreq_unregister_driver(&powernv_cpufreq_driver);
+}
+
+module_init(powernv_cpufreq_init);
+module_exit(powernv_cpufreq_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>");

-- 
1.8.3.1

From: "Srivatsa S. Bhat" <redacted>

On POWER systems, the CPU frequency is controlled at a core-level and
hence we need to serialize so that only one of the threads in the core
switches the core's frequency at a time.

Using a global mutex lock would needlessly serialize _all_ frequency
transitions in the system (across all cores). So introduce per-core
locking to enable finer-grained synchronization and thereby enhance
the speed and responsiveness of the cpufreq driver to varying workload
demands.

The design of per-core locking is very simple and straight-forward: we
first define a Per-CPU lock and use the ones that belongs to the first
thread sibling of the core.

cpu_first_thread_sibling() macro is used to find the *common* lock for
all thread siblings belonging to a core.

Signed-off-by: Srivatsa S. Bhat <redacted>
Signed-off-by: Vaidyanathan Srinivasan <redacted>
Signed-off-by: Gautham R. Shenoy <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index ab1551f..66dae0d 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -24,8 +24,15 @@
 #include <linux/of.h>
 #include <asm/cputhreads.h>
 
-/* FIXME: Make this per-core */
-static DEFINE_MUTEX(freq_switch_mutex);
+/* Per-Core locking for frequency transitions */
+static DEFINE_PER_CPU(struct mutex, freq_switch_lock);
+
+#define lock_core_freq(cpu)				\
+			mutex_lock(&per_cpu(freq_switch_lock,\
+				cpu_first_thread_sibling(cpu)));
+#define unlock_core_freq(cpu)				\
+			mutex_unlock(&per_cpu(freq_switch_lock,\
+				cpu_first_thread_sibling(cpu)));
 
 #define POWERNV_MAX_PSTATES	256
 

@@ -221,7 +228,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy,
 	freqs.new = powernv_freqs[new_index].frequency;
 	freqs.cpu = policy->cpu;
 
-	mutex_lock(&freq_switch_mutex);
+	lock_core_freq(policy->cpu);
 	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
 
 	pr_debug("setting frequency for cpu %d to %d kHz index %d pstate %d",

@@ -233,7 +240,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy,
 	rc = powernv_set_freq(policy->cpus, new_index);
 
 	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
-	mutex_unlock(&freq_switch_mutex);
+	unlock_core_freq(policy->cpu);
 
 	return rc;
 }

@@ -250,7 +257,7 @@ static struct cpufreq_driver powernv_cpufreq_driver = {
 
 static int __init powernv_cpufreq_init(void)
 {
-	int rc = 0;
+	int cpu, rc = 0;
 
 	/* Discover pstates from device tree and init */
 

@@ -260,6 +267,10 @@ static int __init powernv_cpufreq_init(void)
 		pr_info("powernv-cpufreq disabled\n");
 		return rc;
 	}
+	/* Init per-core mutex */
+	for_each_possible_cpu(cpu) {
+		mutex_init(&per_cpu(freq_switch_lock, cpu));
+	}
 
 	rc = cpufreq_register_driver(&powernv_cpufreq_driver);
 	return rc;

-- 
1.8.3.1

From: "Gautham R. Shenoy" <redacted>

Create a driver attribute named cpuinfo_nominal_freq which
creates a sysfs read-only file named cpuinfo_nominal_freq. Export
the frequency corresponding to the nominal_pstate through this
interface.

Nominal frequency is the highest non-turbo frequency for the
platform.  This is generally used for setting governor policies from
user space for optimal energy efficiency.

Signed-off-by: Gautham R. Shenoy <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index e7b0292..46bee8a 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -142,8 +142,30 @@ static unsigned int pstate_id_to_freq(int pstate_id)
 	return powernv_freqs[i].frequency;
 }
 
+/**
+ * show_cpuinfo_nominal_freq - Show the nominal CPU frequency as indicated by
+ * the firmware
+ */
+static ssize_t show_cpuinfo_nominal_freq(struct cpufreq_policy *policy,
+					char *buf)
+{
+	int nominal_freq;
+	nominal_freq = pstate_id_to_freq(powernv_pstate_info.pstate_nominal_id);
+	return sprintf(buf, "%u\n", nominal_freq);
+}
+
+
+struct freq_attr cpufreq_freq_attr_cpuinfo_nominal_freq = {
+	.attr = { .name = "cpuinfo_nominal_freq",
+		  .mode = 0444,
+		},
+	.show = show_cpuinfo_nominal_freq,
+};
+
+
 static struct freq_attr *powernv_cpu_freq_attr[] = {
 	&cpufreq_freq_attr_scaling_available_freqs,
+	&cpufreq_freq_attr_cpuinfo_nominal_freq,
 	NULL,
 };
 

-- 
1.8.3.1

From: "Gautham R. Shenoy" <redacted>

Create a helper routine that can return the cpu-frequency for the
corresponding pstate_id.

Also, cache the values of the pstate_max, pstate_min and
pstate_nominal and nr_pstates in a static structure so that they can
be reused in the future to perform any validations.

Signed-off-by: Gautham R. Shenoy <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 66dae0d..e7b0292 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -39,6 +39,14 @@ static DEFINE_PER_CPU(struct mutex, freq_switch_lock);
 static struct cpufreq_frequency_table powernv_freqs[POWERNV_MAX_PSTATES+1];
 static int powernv_pstate_ids[POWERNV_MAX_PSTATES+1];
 
+struct powernv_pstate_info {
+	int pstate_min_id;
+	int pstate_max_id;
+	int pstate_nominal_id;
+	int nr_pstates;
+};
+static struct powernv_pstate_info powernv_pstate_info;
+
 /*
  * Initialize the freq table based on data obtained
  * from the firmware passed via device-tree

@@ -112,9 +120,28 @@ static int init_powernv_pstates(void)
 	for (i = 0; powernv_freqs[i].frequency != CPUFREQ_TABLE_END; i++)
 		pr_debug("%d: %d\n", i, powernv_freqs[i].frequency);
 
+	powernv_pstate_info.pstate_min_id = pstate_min;
+	powernv_pstate_info.pstate_max_id = pstate_max;
+	powernv_pstate_info.pstate_nominal_id = pstate_nominal;
+	powernv_pstate_info.nr_pstates = nr_pstates;
+
 	return 0;
 }
 
+/**
+ * Returns the cpu frequency corresponding to the pstate_id.
+ */
+static unsigned int pstate_id_to_freq(int pstate_id)
+{
+	int i;
+
+	i = powernv_pstate_info.pstate_max_id - pstate_id;
+
+	BUG_ON(i >= powernv_pstate_info.nr_pstates || i < 0);
+	WARN_ON(powernv_pstate_ids[i] != pstate_id);
+	return powernv_freqs[i].frequency;
+}
+
 static struct freq_attr *powernv_cpu_freq_attr[] = {
 	&cpufreq_freq_attr_scaling_available_freqs,
 	NULL,

-- 
1.8.3.1

From: "Gautham R. Shenoy" <redacted>

The current frequency of a cpu is reported through the sysfs file
cpuinfo_cur_freq. This requires the driver to implement a
"->get(unsigned int cpu)" method which will return the current
operating frequency.

Implement a function named powernv_cpufreq_get() which reads the local
pstate from the PMSR and returns the corresponding frequency.

Set the powernv_cpufreq_driver.get hook to powernv_cpufreq_get().

Signed-off-by: Gautham R. Shenoy <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 46bee8a..ef6ed8c 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -206,6 +206,43 @@ static inline void set_pmspr(unsigned long sprn, unsigned long val)
 	BUG();
 }
 
+/*
+ * Computes the current frequency on this cpu
+ * and stores the result in *ret_freq.
+ */
+static void powernv_read_cpu_freq(void *ret_freq)
+{
+	unsigned long pmspr_val;
+	s8 local_pstate_id;
+	int *cur_freq, freq, pstate_id;
+
+	cur_freq = (int *)ret_freq;
+	pmspr_val = get_pmspr(SPRN_PMSR);
+
+	/* The local pstate id corresponds bits 48..55 in the PMSR.
+         * Note: Watch out for the sign! */
+	local_pstate_id = (pmspr_val >> 48) & 0xFF;
+	pstate_id = local_pstate_id;
+
+	freq = pstate_id_to_freq(pstate_id);
+	pr_debug("cpu %d pmsr %lx pstate_id %d frequency %d \n",
+		smp_processor_id(), pmspr_val, pstate_id, freq);
+	*cur_freq = freq;
+}
+
+/*
+ * Returns the cpu frequency as reported by the firmware for 'cpu'.
+ * This value is reported through the sysfs file cpuinfo_cur_freq.
+ */
+unsigned int powernv_cpufreq_get(unsigned int cpu)
+{
+	int ret_freq;
+
+	smp_call_function_any(cpu_sibling_mask(cpu), powernv_read_cpu_freq,
+			&ret_freq, 1);
+	return ret_freq;
+}
+
 static void set_pstate(void *pstate)
 {
 	unsigned long val;

@@ -297,6 +334,7 @@ static int powernv_cpufreq_target(struct cpufreq_policy *policy,
 static struct cpufreq_driver powernv_cpufreq_driver = {
 	.verify		= powernv_cpufreq_verify,
 	.target		= powernv_cpufreq_target,
+	.get		= powernv_cpufreq_get,
 	.init		= powernv_cpufreq_cpu_init,
 	.exit		= powernv_cpufreq_cpu_exit,
 	.name		= "powernv-cpufreq",

-- 
1.8.3.1

On Thu, Mar 20, 2014 at 05:40:57PM +0530, Gautham R. Shenoy wrote:

From: "Srivatsa S. Bhat" <redacted>

On POWER systems, the CPU frequency is controlled at a core-level and
hence we need to serialize so that only one of the threads in the core
switches the core's frequency at a time.

Using a global mutex lock would needlessly serialize _all_ frequency
transitions in the system (across all cores). So introduce per-core
locking to enable finer-grained synchronization and thereby enhance
the speed and responsiveness of the cpufreq driver to varying workload
demands.

The design of per-core locking is very simple and straight-forward: we
first define a Per-CPU lock and use the ones that belongs to the first
thread sibling of the core.

cpu_first_thread_sibling() macro is used to find the *common* lock for
all thread siblings belonging to a core.

Forgot to add the following line.

Reviewed-by: Preeti U Murthy <redacted>

On Thu, Mar 20, 2014 at 05:40:58PM +0530, Gautham R. Shenoy wrote:

From: "Gautham R. Shenoy" <redacted>

Create a helper routine that can return the cpu-frequency for the
corresponding pstate_id.

Also, cache the values of the pstate_max, pstate_min and
pstate_nominal and nr_pstates in a static structure so that they can
be reused in the future to perform any validations.

Forgot to add the following line:

  Reviewed-by: Preeti U Murthy [off-list ref]

On Thu, Mar 20, 2014 at 05:41:00PM +0530, Gautham R. Shenoy wrote:

From: "Gautham R. Shenoy" <redacted>

The current frequency of a cpu is reported through the sysfs file
cpuinfo_cur_freq. This requires the driver to implement a
"->get(unsigned int cpu)" method which will return the current
operating frequency.

Implement a function named powernv_cpufreq_get() which reads the local
pstate from the PMSR and returns the corresponding frequency.

Set the powernv_cpufreq_driver.get hook to powernv_cpufreq_get().

Forgot to add 

  Reviewed-by: Preeti U Murthy [off-list ref]

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

This is the v3 of the consolidated patchset consisting
patches for enabling cpufreq on IBM POWERNV platforms
along with some enhancements.

This is the first time I saw them. Looks like you never Cc'd linux-pm list.
Also, would be better to keep Maintainers in --to field so that they can
review them as soon as possible. Otherwise they might stay on lists for
a long time..

Hi Viresh,

On Fri, Mar 21, 2014 at 01:16:03PM +0530, Viresh Kumar wrote:

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

quoted

This is the v3 of the consolidated patchset consisting
patches for enabling cpufreq on IBM POWERNV platforms
along with some enhancements.

This is the first time I saw them. Looks like you never Cc'd linux-pm list.
Also, would be better to keep Maintainers in --to field so that they can
review them as soon as possible. Otherwise they might stay on lists for
a long time..

Yes, I hadn't Cc'ed linux-pm list last time around. Sorry about
that. Will keep this in mind the next time around. Also, your
suggestion regarding keeping the Maintainers in --to field is well
taken.

--
Thanks and Regards
gautham.

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

From: Vaidyanathan Srinivasan <redacted>

Hi Vaidy,

Probably we should remove SA1100's entry as well from here. This is
not the right way of doing it. Imagine 100 platforms having entries here.
If you want it, then select it from your platforms Kconfig.

Nice :)

People normally do this from the defconfigs instead. And logically speaking
we might better have only dependencies here, isn't it? And obviously
governors aren't a dependency for this driver. :)

That's it? Sure?

Even if things compile for you, you must explicitly include all the
files on which
you depend.

Why do you want to continue here?

I don't think you are using this field at all and this is the field you can
use for driver_data and so you can get rid of powernv_pstate_ids[ ].

Not required.

You have already printed this table earlier..

Can use this instead: cpufreq_generic_attr?

Looks big enough not be inlined?

Same here..

Why not sending value only to this routine instead of pointer?

Maybe a blank line here?

+       /* Set both global(bits 56..63) and local(bits 48..55) PStates */
+       val = val | (pstate_ul << 56) | (pstate_ul << 48);

here as well?

I think automatic type conversion will happen here.

Hmm, interesting I also feel there are cases where this routine can
get called from other CPUs. Can you list those use cases where it can
happen? Governors will mostly call this from one of the CPUs present
in policy->cpus.

What will break if you don't have this ifdef here? Without that as well
below code should work?

This doesn't exist anymore.

+       return cpufreq_frequency_table_cpuinfo(policy, powernv_freqs);

Have you written this driver long time back? CPUFreq core has been
cleaned up heavily since last few kernel releases and I think there are
better helper routines available now.

You don't need this..

use generic verify function pointer instead..

use target_index() instead..

Why do you need this lock for?

I think you have Srivatsa there who has seen lots of cpufreq code and
could have helped you a lot :)

Would be better if you keep these callbacks in the order they are declared
in cpufreq.h..

Remove blank line.

+       rc = init_powernv_pstates();
+

same here..

Merge above two lines.

Place these right after the routines without any blank lines in between.

+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>");

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

From: "Srivatsa S. Bhat" <redacted>

On POWER systems, the CPU frequency is controlled at a core-level and
hence we need to serialize so that only one of the threads in the core
switches the core's frequency at a time.

Probably you don't need this anymore.

https://lkml.org/lkml/2014/3/21/23

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

return sprintf(buf, "%u\n",
pstate_id_to_freq(powernv_pstate_info.pstate_nominal_id));

??

remove extra blank line.

Align {}

On Thu, Mar 20, 2014 at 5:41 PM, Gautham R. Shenoy
[off-list ref] wrote:

From: "Gautham R. Shenoy" <redacted>

The current frequency of a cpu is reported through the sysfs file
cpuinfo_cur_freq. This requires the driver to implement a
"->get(unsigned int cpu)" method which will return the current
operating frequency.

Implement a function named powernv_cpufreq_get() which reads the local
pstate from the PMSR and returns the corresponding frequency.

Set the powernv_cpufreq_driver.get hook to powernv_cpufreq_get().

Signed-off-by: Gautham R. Shenoy <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

Please merge these fixups with the first patch which is creating the driver.
I understand that a different guy has created this patch and so wanted
to have a patch on his name but its really difficult to review this way.
Better add your signed-off in the first patch instead. Sending such changes
once the driver is mainlined looks fine.

You don't need cur_freq variable at all..

similarly local_pstate_id

Move above print here after a blank line. Also remove freq variable as
well and use *cur_freq directly.. And then you can rename it to freq as well.

On Fri, Mar 21, 2014 at 02:17:28PM +0530, Viresh Kumar wrote:

quoted

+static ssize_t show_cpuinfo_nominal_freq(struct cpufreq_policy *policy,
+                                       char *buf)
+{
+       int nominal_freq;
+       nominal_freq = pstate_id_to_freq(powernv_pstate_info.pstate_nominal_id);
+       return sprintf(buf, "%u\n", nominal_freq);

return sprintf(buf, "%u\n",
pstate_id_to_freq(powernv_pstate_info.pstate_nominal_id));

Sure. Will fix this. 

??

quoted

+}
+
+

remove extra blank line.

quoted

+struct freq_attr cpufreq_freq_attr_cpuinfo_nominal_freq = {
+       .attr = { .name = "cpuinfo_nominal_freq",
+                 .mode = 0444,
+               },

Align {}

Probably the use of ATTR_RO(cpuinfo_nominal_freq) and renaming
show_cpuinfo_nominal_freq to cpuinfo_nominal_freq_show() would be even
better. What do you think ?

quoted

+       .show = show_cpuinfo_nominal_freq,
+};
+
+
 static struct freq_attr *powernv_cpu_freq_attr[] = {
        &cpufreq_freq_attr_scaling_available_freqs,
+       &cpufreq_freq_attr_cpuinfo_nominal_freq,
        NULL,
 };

This needs to be rewritten to include the entries of cpufreq_generic_attr.

Thanks for the review.

--
Regards
gautham. 

On 03/21/2014 02:12 PM, Viresh Kumar wrote:

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

quoted

From: "Srivatsa S. Bhat" <redacted>

On POWER systems, the CPU frequency is controlled at a core-level and
hence we need to serialize so that only one of the threads in the core
switches the core's frequency at a time.

Probably you don't need this anymore.

https://lkml.org/lkml/2014/3/21/23

Agreed.

Regards,
Srivatsa S. Bhat

On 21 March 2014 15:25, Gautham R Shenoy [off-list ref] wrote:

Probably the use of ATTR_RO(cpuinfo_nominal_freq) and renaming
show_cpuinfo_nominal_freq to cpuinfo_nominal_freq_show() would be even
better. What do you think ?

+1

Hi Viresh,

On Fri, Mar 21, 2014 at 02:11:32PM +0530, Viresh Kumar wrote:

On Thu, Mar 20, 2014 at 5:40 PM, Gautham R. Shenoy
[off-list ref] wrote:

quoted

From: Vaidyanathan Srinivasan <redacted>

Hi Vaidy,

quoted

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 4b029c0..4ba1632 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig

@@ -48,6 +48,7 @@ config CPU_FREQ_STAT_DETAILS
 choice
        prompt "Default CPUFreq governor"
        default CPU_FREQ_DEFAULT_GOV_USERSPACE if ARM_SA1100_CPUFREQ || ARM_SA1110_CPUFREQ
+       default CPU_FREQ_DEFAULT_GOV_ONDEMAND if POWERNV_CPUFREQ

Probably we should remove SA1100's entry as well from here. This is
not the right way of doing it. Imagine 100 platforms having entries here.
If you want it, then select it from your platforms Kconfig.

Sure. Will move these bits and the other governor related bits to the
Powernv Kconfig.

quoted

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
new file mode 100644
index 0000000..ab1551f
--- /dev/null
+
+#define pr_fmt(fmt)    "powernv-cpufreq: " fmt
+
+#include <linux/module.h>
+#include <linux/cpufreq.h>
+#include <linux/of.h>
+#include <asm/cputhreads.h>

That's it? Sure?

Even if things compile for you, you must explicitly include all the
files on which
you depend.

Ok. 

quoted

+
+       WARN_ON(len_ids != len_freqs);
+       nr_pstates = min(len_ids, len_freqs) / sizeof(u32);
+       WARN_ON(!nr_pstates);

Why do you want to continue here?

Good point. We might be better off exiting at this point. 

quoted

+       pr_debug("NR PStates %d\n", nr_pstates);
+       for (i = 0; i < nr_pstates; i++) {
+               u32 id = be32_to_cpu(pstate_ids[i]);
+               u32 freq = be32_to_cpu(pstate_freqs[i]);
+
+               pr_debug("PState id %d freq %d MHz\n", id, freq);
+               powernv_freqs[i].driver_data = i;

I don't think you are using this field at all and this is the field you can
use for driver_data and so you can get rid of powernv_pstate_ids[ ].

Using driver_data to record powernv_pstate_ids won't work since
powernv_pstate_ids can be negative. So a pstate_id -3 can be confused
with CPUFREQ_BOOST_FREQ thereby not displaying the frequency
corresponding to pstate id -3. So for now I think we will be retaining
powernv_pstate_ids.

quoted

+               powernv_freqs[i].frequency = freq * 1000; /* kHz */
+               powernv_pstate_ids[i] = id;
+       }
+       /* End of list marker entry */
+       powernv_freqs[i].driver_data = 0;

Not required.

Ok.

quoted

+       powernv_freqs[i].frequency = CPUFREQ_TABLE_END;
+
+       /* Print frequency table */
+       for (i = 0; powernv_freqs[i].frequency != CPUFREQ_TABLE_END; i++)
+               pr_debug("%d: %d\n", i, powernv_freqs[i].frequency);

You have already printed this table earlier..

Fair enough.

quoted

+
+       return 0;
+}
+
+static struct freq_attr *powernv_cpu_freq_attr[] = {
+       &cpufreq_freq_attr_scaling_available_freqs,
+       NULL,
+};

Can use this instead: cpufreq_generic_attr?

In this patch yes. But later patch introduces an additional attribute
for displaying the nominal frequency. Will handle that part in a clean
way in the next version.

quoted

+/* Helper routines */
+
+/* Access helpers to power mgt SPR */
+
+static inline unsigned long get_pmspr(unsigned long sprn)

Looks big enough not be inlined?

It is called from one function. It has been defined separately for
readability. 

quoted

+{
+       switch (sprn) {
+       case SPRN_PMCR:
+               return mfspr(SPRN_PMCR);
+
+       case SPRN_PMICR:
+               return mfspr(SPRN_PMICR);
+
+       case SPRN_PMSR:
+               return mfspr(SPRN_PMSR);
+       }
+       BUG();
+}
+
+static inline void set_pmspr(unsigned long sprn, unsigned long val)
+{

Same here..

Same reason as above.

quoted

+       switch (sprn) {
+       case SPRN_PMCR:
+               mtspr(SPRN_PMCR, val);
+               return;
+
+       case SPRN_PMICR:
+               mtspr(SPRN_PMICR, val);
+               return;
+
+       case SPRN_PMSR:
+               mtspr(SPRN_PMSR, val);
+               return;
+       }
+       BUG();
+}
+
+static void set_pstate(void *pstate)
+{
+       unsigned long val;
+       unsigned long pstate_ul = *(unsigned long *) pstate;

Why not sending value only to this routine instead of pointer?

Well this function is called via an smp_call_function. so, cannot send
a value :(

quoted

+
+       val = get_pmspr(SPRN_PMCR);
+       val = val & 0x0000ffffffffffffULL;

Maybe a blank line here?

Ok.

quoted

+       /* Set both global(bits 56..63) and local(bits 48..55) PStates */
+       val = val | (pstate_ul << 56) | (pstate_ul << 48);

here as well?

Ok.

quoted

+       pr_debug("Setting cpu %d pmcr to %016lX\n", smp_processor_id(), val);
+       set_pmspr(SPRN_PMCR, val);
+}
+
+static int powernv_set_freq(cpumask_var_t cpus, unsigned int new_index)
+{
+       unsigned long val = (unsigned long) powernv_pstate_ids[new_index];

I think automatic type conversion will happen here.

Ok. Will fix this.

quoted

+
+       /*
+        * Use smp_call_function to send IPI and execute the
+        * mtspr on target cpu.  We could do that without IPI
+        * if current CPU is within policy->cpus (core)
+        */

Hmm, interesting I also feel there are cases where this routine can
get called from other CPUs. Can you list those use cases where it can
happen? Governors will mostly call this from one of the CPUs present
in policy->cpus.

Consider the case when the governor is userspace and we are executing 

    # echo freqvalue  > 
         /sys/devices/system/cpu/cpu<i>/cpufreq/scaling_setspeed 

from a cpu <j> which is not in policy->cpus of cpu i. 

quoted

+static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+       int base, i;
+
+#ifdef CONFIG_SMP

What will break if you don't have this ifdef here? Without that as well
below code should work?

quoted

+       base = cpu_first_thread_sibling(policy->cpu);
+
+       for (i = 0; i < threads_per_core; i++)
+               cpumask_set_cpu(base + i, policy->cpus);
+#endif
+       policy->cpuinfo.transition_latency = 25000;
+
+       policy->cur = powernv_freqs[0].frequency;
+       cpufreq_frequency_table_get_attr(powernv_freqs, policy->cpu);

This doesn't exist anymore.

Didn't get this comment!

quoted

+       return cpufreq_frequency_table_cpuinfo(policy, powernv_freqs);

Have you written this driver long time back? CPUFreq core has been
cleaned up heavily since last few kernel releases and I think there are
better helper routines available now.

Yup it was written quite a while ago. And yeah, CPUFreq has changed
quite a bit since the last time I saw it :-)

quoted

+}
+
+static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+       cpufreq_frequency_table_put_attr(policy->cpu);
+       return 0;
+}

You don't need this..

Why not ?

quoted

+static int powernv_cpufreq_verify(struct cpufreq_policy *policy)
+{
+       return cpufreq_frequency_table_verify(policy, powernv_freqs);
+}

use generic verify function pointer instead..

quoted

+static int powernv_cpufreq_target(struct cpufreq_policy *policy,
+                             unsigned int target_freq,
+                             unsigned int relation)

use target_index() instead..

quoted

+{
+       int rc;
+       struct cpufreq_freqs freqs;
+       unsigned int new_index;
+
+       cpufreq_frequency_table_target(policy, powernv_freqs, target_freq,
+                                      relation, &new_index);
+
+       freqs.old = policy->cur;
+       freqs.new = powernv_freqs[new_index].frequency;
+       freqs.cpu = policy->cpu;
+
+       mutex_lock(&freq_switch_mutex);

Why do you need this lock for?

I guess it was to serialize accesses to PMCR. But Srivatsa's patch
converts this to a per-core lock which probably is no longer required
after your cpufreq_freq_transition_begin/end() patch series.

quoted

+       cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
+
+       pr_debug("setting frequency for cpu %d to %d kHz index %d pstate %d",
+                policy->cpu,
+                powernv_freqs[new_index].frequency,
+                new_index,
+                powernv_pstate_ids[new_index]);
+
+       rc = powernv_set_freq(policy->cpus, new_index);
+
+       cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
+       mutex_unlock(&freq_switch_mutex);
+
+       return rc;
+}
+
+static struct cpufreq_driver powernv_cpufreq_driver = {
+       .verify         = powernv_cpufreq_verify,
+       .target         = powernv_cpufreq_target,

I think you have Srivatsa there who has seen lots of cpufreq code and
could have helped you a lot :)

quoted

+       .init           = powernv_cpufreq_cpu_init,
+       .exit           = powernv_cpufreq_cpu_exit,
+       .name           = "powernv-cpufreq",
+       .flags          = CPUFREQ_CONST_LOOPS,
+       .attr           = powernv_cpu_freq_attr,

Would be better if you keep these callbacks in the order they are declared
in cpufreq.h..

Sure.

quoted

+module_init(powernv_cpufreq_init);
+module_exit(powernv_cpufreq_exit);

Place these right after the routines without any blank lines in

between.

Is this the new convention ?

quoted

+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Vaidyanathan Srinivasan <svaidy at linux.vnet.ibm.com>");

Thanks for the detailed review.

--
Regards
gautham.

On 21 March 2014 16:13, Gautham R Shenoy [off-list ref] wrote:

On Fri, Mar 21, 2014 at 02:11:32PM +0530, Viresh Kumar wrote:

quoted

quoted

+               pr_debug("PState id %d freq %d MHz\n", id, freq);
+               powernv_freqs[i].driver_data = i;

I don't think you are using this field at all and this is the field you can
use for driver_data and so you can get rid of powernv_pstate_ids[ ].

Using driver_data to record powernv_pstate_ids won't work since
powernv_pstate_ids can be negative. So a pstate_id -3 can be confused
with CPUFREQ_BOOST_FREQ thereby not displaying the frequency
corresponding to pstate id -3. So for now I think we will be retaining
powernv_pstate_ids.

As I said earlier, this field is only used by cpufreq drivers and cpufreq core
isn't supposed to touch it. CPUFREQ_BOOST_FREQ and other macros
are there for .frequency field and not this one.

quoted

quoted

+static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+       int base, i;
+
+#ifdef CONFIG_SMP

What will break if you don't have this ifdef here? Without that as well
below code should work?

Missed this one?

quoted

quoted

+       base = cpu_first_thread_sibling(policy->cpu);
+
+       for (i = 0; i < threads_per_core; i++)
+               cpumask_set_cpu(base + i, policy->cpus);
+#endif
+       policy->cpuinfo.transition_latency = 25000;
+
+       policy->cur = powernv_freqs[0].frequency;
+       cpufreq_frequency_table_get_attr(powernv_freqs, policy->cpu);

This doesn't exist anymore.

Didn't get this comment!

cpufreq_frequency_table_get_attr() routine doesn't exist anymore.

quoted

quoted

+static int powernv_cpufreq_cpu_exit(struct cpufreq_policy *policy)
+{
+       cpufreq_frequency_table_put_attr(policy->cpu);
+       return 0;
+}

You don't need this..

Why not ?

Because cpufreq_frequency_table_get_attr() and
cpufreq_frequency_table_put_attr() don't exist anymore :)

quoted

quoted

+module_init(powernv_cpufreq_init);
+module_exit(powernv_cpufreq_exit);

Place these right after the routines without any blank lines in

between.

Is this the new convention ?

Don't know I have been following this since long time, probably from the
time I started with Mainline stuff.. I have seen many maintainers advising this
as it make code more readable, specially if these routines are quite big..

Probably it isn't mentioned in coding guidelines but people follow it most of
the times.

On Fri, Mar 21, 2014 at 03:01:29PM +0530, Viresh Kumar wrote:

On Thu, Mar 20, 2014 at 5:41 PM, Gautham R. Shenoy
[off-list ref] wrote:

quoted

From: "Gautham R. Shenoy" <redacted>

The current frequency of a cpu is reported through the sysfs file
cpuinfo_cur_freq. This requires the driver to implement a
"->get(unsigned int cpu)" method which will return the current
operating frequency.

Implement a function named powernv_cpufreq_get() which reads the local
pstate from the PMSR and returns the corresponding frequency.

Set the powernv_cpufreq_driver.get hook to powernv_cpufreq_get().

Signed-off-by: Gautham R. Shenoy <redacted>
---
 drivers/cpufreq/powernv-cpufreq.c | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

Please merge these fixups with the first patch which is creating the driver.
I understand that a different guy has created this patch and so wanted
to have a patch on his name but its really difficult to review this

way.

Heh! Well, that wasn't the reason why this was sent out as a separate
patch, but never mind. Though I don't understand why it would be
difficult to review the patch though.

Better add your signed-off in the first patch instead. Sending such changes
once the driver is mainlined looks fine.

Sure, this makes sense.

quoted

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 46bee8a..ef6ed8c 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -206,6 +206,43 @@ static inline void set_pmspr(unsigned long sprn, unsigned long val)
        BUG();
 }

+/*
+ * Computes the current frequency on this cpu
+ * and stores the result in *ret_freq.
+ */
+static void powernv_read_cpu_freq(void *ret_freq)
+{
+       unsigned long pmspr_val;
+       s8 local_pstate_id;
+       int *cur_freq, freq, pstate_id;
+
+       cur_freq = (int *)ret_freq;

You don't need cur_freq variable at all..

I don't like it either. But the compiler complains without this hack
:-(

quoted

+       pmspr_val = get_pmspr(SPRN_PMSR);
+
+       /* The local pstate id corresponds bits 48..55 in the PMSR.
+         * Note: Watch out for the sign! */
+       local_pstate_id = (pmspr_val >> 48) & 0xFF;
+       pstate_id = local_pstate_id;

similarly local_pstate_id

well, I am interested in the bits 48..55 of pmspr_val. That's the
pstate_id which can be negative. So I'll like to keep
local_pstate_id. 

quoted

+
+       freq = pstate_id_to_freq(pstate_id);
+       pr_debug("cpu %d pmsr %lx pstate_id %d frequency %d \n",
+               smp_processor_id(), pmspr_val, pstate_id, freq);
+       *cur_freq = freq;

Move above print here after a blank line. Also remove freq variable as
well and use *cur_freq directly.. And then you can rename it to freq

as well.

We can get rid of freq and use *cur_freq in its place.


Thanks for the detailed review.

--
Regards
gautham.

On 03/21/2014 04:24 PM, Viresh Kumar wrote:

On 21 March 2014 16:13, Gautham R Shenoy [off-list ref] wrote:

quoted

On Fri, Mar 21, 2014 at 02:11:32PM +0530, Viresh Kumar wrote:

quoted

quoted

quoted

+               pr_debug("PState id %d freq %d MHz\n", id, freq);
+               powernv_freqs[i].driver_data = i;

[...] 

quoted

quoted

quoted

+static int powernv_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+       int base, i;
+
+#ifdef CONFIG_SMP

What will break if you don't have this ifdef here? Without that as well
below code should work?

Missed this one?