[PATCH v3 1/1] powerpc/pseries: Interface to represent PAPR firmware attributes

[Pratik R. Sampat]

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 <psampat@xxxxxxxxxxxxx>
Reviewed-by: Gautham R. Shenoy <ego@xxxxxxxxxxxxxxxxxx>
---
 .../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        | 320 ++++++++++++++++++
 5 files changed, 372 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..fd82f2bfafe5
--- /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@xxxxxxxxxx>
+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@xxxxxxxxxx>
+Description:	Energy, frequency attributes directory for POWERVM servers
+
+		This directory provides energy, erequency, 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 e3b29eda8074..c91714ea6719 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -316,7 +316,8 @@
 #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)
@@ -631,6 +632,27 @@ 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 c8a2b0b05ac0..d14fca89ac25 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..43c620132b4d
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/papr_platform_attributes.c
@@ -0,0 +1,320 @@
+// 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 <linux/module.h>
+#include <linux/types.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/hugetlb.h>
+#include <asm/lppaca.h>
+#include <asm/hvcall.h>
+#include <asm/firmware.h>
+#include <asm/time.h>
+#include <asm/prom.h>
+#include <asm/vdso_datapage.h>
+#include <asm/vio.h>
+#include <asm/mmu.h>
+#include <asm/machdep.h>
+#include <asm/drmem.h>
+
+#include "pseries.h"
+
+#define MAX_ATTRS		3
+#define MAX_NAME_LEN		16
+
+/*
+ * 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)
+
+struct papr_attr {
+	u64 id;
+	struct kobj_attribute kobj_attr;
+};
+struct papr_group {
+	char name[MAX_NAME_LEN];
+	struct attribute_group pg;
+	struct papr_attr *pgattrs;
+} *pgs;
+
+/* /sys/firmware/papr */
+struct kobject *papr_kobj;
+/* /sys/firmware/papr/energy_scale_info */
+struct kobject *esi_kobj;
+
+struct h_energy_scale_info_hdr *esi_hdr;
+struct energy_scale_attribute *esi_attrs;
+
+/*
+ * Extract and export the description of the energy scale attribute
+ *
+ * As We do not expect the name to change, hence use the old description and
+ * save a call to the H_GET_ENERGY_SCALE_INFO HCALL
+ */
+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);
+	int idx, ret = 0;
+
+	for (idx = 0; idx < be64_to_cpu(esi_hdr->num_attrs); idx++) {
+		if (pattr->id == be64_to_cpu(esi_attrs[idx].id)) {
+			ret = sprintf(buf, "%s\n", esi_attrs[idx].desc);
+			if (ret < 0)
+				ret = -EIO;
+			break;
+		}
+	}
+
+	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);
+	char *t_buf;
+	struct h_energy_scale_info_hdr *t_hdr;
+	struct energy_scale_attribute *t_esi;
+	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 = sprintf(buf, "%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);
+	char *t_buf;
+	struct h_energy_scale_info_hdr *t_hdr;
+	struct energy_scale_attribute *t_esi;
+	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 = sprintf(buf, "%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, int len, struct papr_group *pg,
+			  bool show_val_desc)
+{
+	int i;
+
+	for (i = 0; i < len; 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);
+}
+
+static int __init papr_init(void)
+{
+	uint64_t num_attrs;
+	int ret, idx, i;
+	char *esi_buf;
+
+	if (!firmware_has_feature(FW_FEATURE_LPAR))
+		return -ENXIO;
+
+	esi_buf = kmalloc(MAX_BUF_SZ, GFP_KERNEL);
+	if (esi_buf == NULL)
+		return -ENOMEM;
+	/*
+	 * 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
+	 */
+	ret = plpar_hcall_norets(H_GET_ENERGY_SCALE_INFO, ESI_FLAGS_ALL, 0,
+				 virt_to_phys(esi_buf), MAX_BUF_SZ);
+	esi_hdr = (struct h_energy_scale_info_hdr *) esi_buf;
+	if (ret != H_SUCCESS || esi_hdr->data_header_version != ESI_VERSION) {
+		pr_warn("hcall failed: H_GET_ENERGY_SCALE_INFO");
+		goto out;
+	}
+
+	num_attrs = be64_to_cpu(esi_hdr->num_attrs);
+	/*
+	 * Typecast the energy buffer to the attribute structure at the offset
+	 * specified in the buffer
+	 */
+	esi_attrs = (struct energy_scale_attribute *)
+		    (esi_buf + be64_to_cpu(esi_hdr->array_offset));
+
+	pgs = kcalloc(num_attrs, sizeof(*pgs), GFP_KERNEL);
+	if (!pgs)
+		goto out_pgs;
+
+	papr_kobj = kobject_create_and_add("papr", firmware_kobj);
+	if (!papr_kobj) {
+		pr_warn("kobject_create_and_add papr failed\n");
+		goto out_kobj;
+	}
+
+	esi_kobj = kobject_create_and_add("energy_scale_info", papr_kobj);
+	if (!esi_kobj) {
+		pr_warn("kobject_create_and_add energy_scale_info failed\n");
+		goto out_ekobj;
+	}
+
+	for (idx = 0; idx < num_attrs; idx++) {
+		char buf[4];
+		bool show_val_desc = true;
+
+		pgs[idx].pgattrs = kcalloc(MAX_ATTRS,
+					   sizeof(*pgs[idx].pgattrs),
+					   GFP_KERNEL);
+		if (!pgs[idx].pgattrs)
+			goto out_kobj;
+
+		pgs[idx].pg.attrs = kcalloc(MAX_ATTRS + 1,
+					    sizeof(*pgs[idx].pg.attrs),
+					    GFP_KERNEL);
+		if (!pgs[idx].pg.attrs) {
+			kfree(pgs[idx].pgattrs);
+			goto out_kobj;
+		}
+
+		sprintf(buf, "%lld", be64_to_cpu(esi_attrs[idx].id));
+		pgs[idx].pg.name = buf;
+
+		/* Do not add the value description if it does not exist */
+		if (strlen(esi_attrs[idx].value_desc) == 0)
+			show_val_desc = false;
+
+		if (add_attr_group(be64_to_cpu(esi_attrs[idx].id),
+				   MAX_ATTRS, &pgs[idx], show_val_desc)) {
+			pr_warn("Failed to create papr attribute group %s\n",
+				pgs[idx].pg.name);
+			goto out_pgattrs;
+		}
+	}
+
+	return 0;
+
+out_pgattrs:
+	for (i = 0; i < MAX_ATTRS; i++) {
+		kfree(pgs[i].pgattrs);
+		kfree(pgs[i].pg.attrs);
+	}
+out_ekobj:
+	kobject_put(esi_kobj);
+out_kobj:
+	kobject_put(papr_kobj);
+out_pgs:
+	kfree(pgs);
+out:
+	kfree(esi_buf);
+
+	return -ENOMEM;
+}
+
+machine_device_initcall(pseries, papr_init);
-- 
2.31.1