Re: [PATCH v8 1/2] powerpc/pseries: Interface to represent PAPR firmware attributes

Adds a generic interface to represent the energy and frequency related
PAPR attributes on the system using the new H_CALL
"H_GET_ENERGY_SCALE_INFO".

H_GET_EM_PARMS H_CALL was previously responsible for exporting this
information in the lparcfg, however the H_GET_EM_PARMS H_CALL
will be deprecated P10 onwards.

The H_GET_ENERGY_SCALE_INFO H_CALL is of the following call format:
hcall(
  uint64 H_GET_ENERGY_SCALE_INFO,  // Get energy scale info
  uint64 flags,           // Per the flag request
  uint64 firstAttributeId,// The attribute id
  uint64 bufferAddress,   // Guest physical address of the output buffer
  uint64 bufferSize       // The size in bytes of the output buffer
);

This H_CALL can query either all the attributes at once with
firstAttributeId = 0, flags = 0 as well as query only one attribute
at a time with firstAttributeId = id, flags = 1.

The output buffer consists of the following
1. number of attributes              - 8 bytes
2. array offset to the data location - 8 bytes
3. version info                      - 1 byte
4. A data array of size num attributes, which contains the following:
  a. attribute ID              - 8 bytes
  b. attribute value in number - 8 bytes
  c. attribute name in string  - 64 bytes
  d. attribute value in string - 64 bytes

The new H_CALL exports information in direct string value format, hence
a new interface has been introduced in
/sys/firmware/papr/energy_scale_info to export this information to
userspace in an extensible pass-through format.

The H_CALL returns the name, numeric value and string value (if exists)

The format of exposing the sysfs information is as follows:
/sys/firmware/papr/energy_scale_info/
   |-- <id>/
     |-- desc
     |-- value
     |-- value_desc (if exists)
   |-- <id>/
     |-- desc
     |-- value
     |-- value_desc (if exists)
...

The energy information that is exported is useful for userspace tools
such as powerpc-utils. Currently these tools infer the
"power_mode_data" value in the lparcfg, which in turn is obtained from
the to be deprecated H_GET_EM_PARMS H_CALL.
On future platforms, such userspace utilities will have to look at the
data returned from the new H_CALL being populated in this new sysfs
interface and report this information directly without the need of
interpretation.

Signed-off-by: Pratik R. Sampat <redacted>
Reviewed-by: Gautham R. Shenoy <redacted>
Reviewed-by: Fabiano Rosas <redacted>
Reviewed-by: Kajol Jain <redacted>
---
 .../sysfs-firmware-papr-energy-scale-info     |  26 ++
 arch/powerpc/include/asm/hvcall.h             |  24 +-
 arch/powerpc/kvm/trace_hv.h                   |   1 +
 arch/powerpc/platforms/pseries/Makefile       |   3 +-
 .../pseries/papr_platform_attributes.c        | 312 ++++++++++++++++++
 5 files changed, 364 insertions(+), 2 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info
 create mode 100644 arch/powerpc/platforms/pseries/papr_platform_attributes.c

diff --git a/Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info b/Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info
new file mode 100644
index 000000000000..139a576c7c9d
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info

@@ -0,0 +1,26 @@
+What:		/sys/firmware/papr/energy_scale_info
+Date:		June 2021
+Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
+Description:	Directory hosting a set of platform attributes like
+		energy/frequency on Linux running as a PAPR guest.
+
+		Each file in a directory contains a platform
+		attribute hierarchy pertaining to performance/
+		energy-savings mode and processor frequency.
+
+What:		/sys/firmware/papr/energy_scale_info/<id>
+		/sys/firmware/papr/energy_scale_info/<id>/desc
+		/sys/firmware/papr/energy_scale_info/<id>/value
+		/sys/firmware/papr/energy_scale_info/<id>/value_desc
+Date:		June 2021
+Contact:	Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
+Description:	Energy, frequency attributes directory for POWERVM servers
+
+		This directory provides energy, frequency, folding information. It
+		contains below sysfs attributes:
+
+		- desc: String description of the attribute <id>
+
+		- value: Numeric value of attribute <id>
+
+		- value_desc: String value of attribute <id>

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index 9bcf345cb208..38980fef7a3d 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h

@@ -323,7 +323,8 @@
 #define H_SCM_PERFORMANCE_STATS 0x418
 #define H_RPT_INVALIDATE	0x448
 #define H_SCM_FLUSH		0x44C
-#define MAX_HCALL_OPCODE	H_SCM_FLUSH
+#define H_GET_ENERGY_SCALE_INFO	0x450
+#define MAX_HCALL_OPCODE	H_GET_ENERGY_SCALE_INFO
 
 /* Scope args for H_SCM_UNBIND_ALL */
 #define H_UNBIND_SCOPE_ALL (0x1)

@@ -641,6 +642,27 @@ struct hv_gpci_request_buffer {
 	uint8_t bytes[HGPCI_MAX_DATA_BYTES];
 } __packed;
 
+#define ESI_VERSION	0x1
+#define MAX_ESI_ATTRS	10
+#define MAX_BUF_SZ	(sizeof(struct h_energy_scale_info_hdr) + \
+			(sizeof(struct energy_scale_attribute) * MAX_ESI_ATTRS))
+
+struct energy_scale_attribute {
+	__be64 id;
+	__be64 value;
+	unsigned char desc[64];
+	unsigned char value_desc[64];
+} __packed;
+
+struct h_energy_scale_info_hdr {
+	__be64 num_attrs;
+	__be64 array_offset;
+	__u8 data_header_version;
+} __packed;
+
+/* /sys/firmware/papr */
+extern struct kobject *papr_kobj;
+
 #endif /* __ASSEMBLY__ */
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_HVCALL_H */

diff --git a/arch/powerpc/kvm/trace_hv.h b/arch/powerpc/kvm/trace_hv.h
index 830a126e095d..38cd0ed0a617 100644
--- a/arch/powerpc/kvm/trace_hv.h
+++ b/arch/powerpc/kvm/trace_hv.h

@@ -115,6 +115,7 @@
 	{H_VASI_STATE,			"H_VASI_STATE"}, \
 	{H_ENABLE_CRQ,			"H_ENABLE_CRQ"}, \
 	{H_GET_EM_PARMS,		"H_GET_EM_PARMS"}, \
+	{H_GET_ENERGY_SCALE_INFO,	"H_GET_ENERGY_SCALE_INFO"}, \
 	{H_SET_MPP,			"H_SET_MPP"}, \
 	{H_GET_MPP,			"H_GET_MPP"}, \
 	{H_HOME_NODE_ASSOCIATIVITY,	"H_HOME_NODE_ASSOCIATIVITY"}, \

diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index 4cda0ef87be0..c4c19f6a5975 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile

@@ -6,7 +6,8 @@ obj-y			:= lpar.o hvCall.o nvram.o reconfig.o \
 			   of_helpers.o \
 			   setup.o iommu.o event_sources.o ras.o \
 			   firmware.o power.o dlpar.o mobility.o rng.o \
-			   pci.o pci_dlpar.o eeh_pseries.o msi.o
+			   pci.o pci_dlpar.o eeh_pseries.o msi.o \
+			   papr_platform_attributes.o
 obj-$(CONFIG_SMP)	+= smp.o
 obj-$(CONFIG_SCANLOG)	+= scanlog.o
 obj-$(CONFIG_KEXEC_CORE)	+= kexec.o

diff --git a/arch/powerpc/platforms/pseries/papr_platform_attributes.c b/arch/powerpc/platforms/pseries/papr_platform_attributes.c
new file mode 100644
index 000000000000..84ddce52e519
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/papr_platform_attributes.c

@@ -0,0 +1,312 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Platform energy and frequency attributes driver
+ *
+ * This driver creates a sys file at /sys/firmware/papr/ which encapsulates a
+ * directory structure containing files in keyword - value pairs that specify
+ * energy and frequency configuration of the system.
+ *
+ * The format of exposing the sysfs information is as follows:
+ * /sys/firmware/papr/energy_scale_info/
+ *  |-- <id>/
+ *    |-- desc
+ *    |-- value
+ *    |-- value_desc (if exists)
+ *  |-- <id>/
+ *    |-- desc
+ *    |-- value
+ *    |-- value_desc (if exists)
+ *
+ * Copyright 2021 IBM Corp.
+ */
+
+#include <asm/hvcall.h>
+#include <asm/machdep.h>
+
+#include "pseries.h"
+
+/*
+ * Flag attributes to fetch either all or one attribute from the HCALL
+ * flag = BE(0) => fetch all attributes with firstAttributeId = 0
+ * flag = BE(1) => fetch a single attribute with firstAttributeId = id
+ */
+#define ESI_FLAGS_ALL		0
+#define ESI_FLAGS_SINGLE	PPC_BIT(0)
+
+#define MAX_ATTRS		3
+
+struct papr_attr {
+	u64 id;
+	struct kobj_attribute kobj_attr;

+};
+struct papr_group {
+	struct attribute_group pg;
+	struct papr_attr pgattrs[MAX_ATTRS];
+} *pgs;
+
+/* /sys/firmware/papr */
+struct kobject *papr_kobj;
+/* /sys/firmware/papr/energy_scale_info */
+struct kobject *esi_kobj;
+
+/*
+ * Extract and export the description of the energy scale attributes
+ */
+static ssize_t papr_show_desc(struct kobject *kobj,
+			       struct kobj_attribute *kobj_attr,
+			       char *buf)
+{
+	struct papr_attr *pattr = container_of(kobj_attr, struct papr_attr,
+					       kobj_attr);
+	struct h_energy_scale_info_hdr *t_hdr;
+	struct energy_scale_attribute *t_esi;
+	char *t_buf;
+	int ret = 0;
+
+	t_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+	if (t_buf == NULL)
+		return -ENOMEM;
+
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_SINGLE,
+				 pattr->id, virt_to_phys(t_buf),
+				 MAX_BUF_SZ);
+
+	if (ret != H_SUCCESS) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	t_hdr = (struct h_energy_scale_info_hdr *) t_buf;
+	t_esi = (struct energy_scale_attribute *)
+		(t_buf + be64_to_cpu(t_hdr->array_offset));
+
+	ret = snprintf(buf, sizeof(t_esi->desc), "%s\n", t_esi->desc);
+	if (ret < 0)
+		ret = -EIO;
+out:
+	kfree(t_buf);
+
+	return ret;
+}
+
+/*
+ * Extract and export the numeric value of the energy scale attributes
+ */
+static ssize_t papr_show_value(struct kobject *kobj,
+				struct kobj_attribute *kobj_attr,
+				char *buf)
+{
+	struct papr_attr *pattr = container_of(kobj_attr, struct papr_attr,
+					       kobj_attr);
+	struct h_energy_scale_info_hdr *t_hdr;
+	struct energy_scale_attribute *t_esi;
+	char *t_buf;
+	int ret = 0;
+
+	t_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+	if (t_buf == NULL)
+		return -ENOMEM;
+
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_SINGLE,
+				 pattr->id, virt_to_phys(t_buf),
+				 MAX_BUF_SZ);
+
+	if (ret != H_SUCCESS) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	t_hdr = (struct h_energy_scale_info_hdr *) t_buf;
+	t_esi = (struct energy_scale_attribute *)
+		(t_buf + be64_to_cpu(t_hdr->array_offset));
+
+	ret = snprintf(buf, sizeof(t_esi->value), "%llu\n",
+		       be64_to_cpu(t_esi->value));

+	if (ret < 0)
+		ret = -EIO;
+out:
+	kfree(t_buf);
+
+	return ret;
+}
+
+/*
+ * Extract and export the value description in string format of the energy
+ * scale attributes
+ */
+static ssize_t papr_show_value_desc(struct kobject *kobj,
+				     struct kobj_attribute *kobj_attr,
+				     char *buf)
+{
+	struct papr_attr *pattr = container_of(kobj_attr, struct papr_attr,
+					       kobj_attr);
+	struct h_energy_scale_info_hdr *t_hdr;
+	struct energy_scale_attribute *t_esi;
+	char *t_buf;
+	int ret = 0;
+
+	t_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+	if (t_buf == NULL)
+		return -ENOMEM;
+
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_SINGLE,
+				 pattr->id, virt_to_phys(t_buf),
+				 MAX_BUF_SZ);
+
+	if (ret != H_SUCCESS) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	t_hdr = (struct h_energy_scale_info_hdr *) t_buf;
+	t_esi = (struct energy_scale_attribute *)
+		(t_buf + be64_to_cpu(t_hdr->array_offset));
+
+	ret = snprintf(buf, sizeof(t_esi->value_desc), "%s\n",
+		       t_esi->value_desc);
+	if (ret < 0)
+		ret = -EIO;
+out:
+	kfree(t_buf);
+
+	return ret;
+}
+
+static struct papr_ops_info {
+	const char *attr_name;
+	ssize_t (*show)(struct kobject *kobj, struct kobj_attribute *kobj_attr,
+			char *buf);
+} ops_info[MAX_ATTRS] = {
+	{ "desc", papr_show_desc },
+	{ "value", papr_show_value },
+	{ "value_desc", papr_show_value_desc },

+};
+
+static void add_attr(u64 id, int index, struct papr_attr *attr)
+{
+	attr->id = id;
+	sysfs_attr_init(&attr->kobj_attr.attr);
+	attr->kobj_attr.attr.name = ops_info[index].attr_name;
+	attr->kobj_attr.attr.mode = 0444;
+	attr->kobj_attr.show = ops_info[index].show;

+}
+
+static int add_attr_group(u64 id, struct papr_group *pg, bool show_val_desc)
+{
+	int i;
+
+	for (i = 0; i < MAX_ATTRS; i++) {
+		if (!strcmp(ops_info[i].attr_name, "value_desc") &&
+		    !show_val_desc) {
+			continue;
+		}
+		add_attr(id, i, &pg->pgattrs[i]);
+		pg->pg.attrs[i] = &pg->pgattrs[i].kobj_attr.attr;
+	}
+
+	return sysfs_create_group(esi_kobj, &pg->pg);