[PATCH 3/8] arm64: pmu: Add support for probing with ACPI

On 06/15/2016 06:33 AM, Will Deacon wrote:

On Thu, Jun 09, 2016 at 05:23:28PM -0500, Jeremy Linton wrote:

quoted

From: Mark Salter <redacted>

In the case of ACPI, the PMU IRQ information is contained in the
MADT table. Also, since the PMU does not exist as a device in the
ACPI DSDT table, it is necessary to create a platform device so
that the appropriate driver probing is triggered.

Signed-off-by: Mark Salter <redacted>
Signed-off-by: Jeremy Linton <redacted>
---

  NOTE: Much of the code in pmu_acpi_init() is replaced in a later version
        of this patch. The later version of the patch cleans up some of the
        possible style/error handling issues that have been pointed out with
        this version.

  arch/arm64/kernel/smp.c      |  5 +++
  drivers/perf/Kconfig         |  4 ++
  drivers/perf/Makefile        |  1 +
  drivers/perf/arm_pmu_acpi.c  | 97 ++++++++++++++++++++++++++++++++++++++++++++
  include/linux/perf/arm_pmu.h |  7 ++++
  5 files changed, 114 insertions(+)
  create mode 100644 drivers/perf/arm_pmu_acpi.c

diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 678e084..5c96d23 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c

@@ -37,6 +37,7 @@
  #include <linux/completion.h>
  #include <linux/of.h>
  #include <linux/irq_work.h>
+#include <linux/perf/arm_pmu.h>

  #include <asm/alternative.h>
  #include <asm/atomic.h>

@@ -540,6 +541,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
  			return;
  		}
  		bootcpu_valid = true;
+		arm_pmu_parse_acpi(0, processor);
  		return;
  	}

@@ -560,6 +562,9 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
  	 */
  	acpi_set_mailbox_entry(cpu_count, processor);

+	/* get PMU irq info */
+	arm_pmu_parse_acpi(cpu_count, processor);
+

Nit: the outer functions are now misnomers, since this has nothing to do
with the GIC. It feels like acpi_parse_gic_cpu_interface could use some
slight restructuring so that the MADT parsing looks less confused.

Ok, I will clean up the naming a bit.

quoted

diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
index acd2397..fd8090d 100644
--- a/drivers/perf/Makefile
+++ b/drivers/perf/Makefile

@@ -1 +1,2 @@
  obj-$(CONFIG_ARM_PMU) += arm_pmu.o
+obj-$(CONFIG_ARM_PMU_ACPI) += arm_pmu_acpi.o

diff --git a/drivers/perf/arm_pmu_acpi.c b/drivers/perf/arm_pmu_acpi.c
new file mode 100644
index 0000000..98c452d
--- /dev/null
+++ b/drivers/perf/arm_pmu_acpi.c

@@ -0,0 +1,97 @@
+/*
+ * PMU support
+ *
+ * Copyright (C) 2015 Red Hat Inc.
+ * Author: Mark Salter <msalter@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <linux/perf/arm_pmu.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+#include <linux/irq.h>
+#include <linux/irqdesc.h>
+
+#define PMU_PDEV_NAME "armv8-pmu"

Stick this in include/linux/perf/arm_pmu.h where we can use it in the driver
code too?

Sure..

quoted

+
+struct pmu_irq {
+	int gsi;
+	int trigger;
+};
+
+static struct pmu_irq pmu_irqs[NR_CPUS] __initdata;
+
+void __init arm_pmu_parse_acpi(int cpu, struct acpi_madt_generic_interrupt *gic)
+{
+	pmu_irqs[cpu].gsi = gic->performance_interrupt;
+	if (gic->flags & ACPI_MADT_PERFORMANCE_IRQ_MODE)
+		pmu_irqs[cpu].trigger = ACPI_EDGE_SENSITIVE;
+	else
+		pmu_irqs[cpu].trigger = ACPI_LEVEL_SENSITIVE;
+}
+
+static int __init pmu_acpi_init(void)
+{
+	struct platform_device *pdev;
+	struct pmu_irq *pirq = pmu_irqs;
+	struct resource	*res, *r;
+	int err = -ENOMEM;
+	int i, count, irq;
+
+	if (acpi_disabled)
+		return 0;
+
+	/* Must have irq for boot boot cpu, at least */

boot boot

quoted

+	if (pirq->gsi == 0)
+		return -EINVAL;
+
+	irq = acpi_register_gsi(NULL, pirq->gsi, pirq->trigger,
+				ACPI_ACTIVE_HIGH);

This is quite tricky to read, thanks to the aliasing of pirq and
pmu_irqs[0]. Why is it necessary to register the first gsi separately,
rather than just register it later in the loop with all the other
interrupts?

	Short answer, no particular reason. If you notice patch 6, 
arm_pmu_acpi_gsi_res() reworks this to register all the irqs for a 
particular PMU at the same time.