powerpc/pseries: Interface to represent PAPR firmware attributes

Adds a syscall 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
);
As specified in PAPR+ v2.11, section 14.14.3.

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 so that the firmware can add new values without the need for
the kernel to be changed.

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 <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Documentation/ABI/testing/sysfs-firmware-papr-energy-scale-info

@@ -0,0 +1,29 @@
+What:		/sys/firmware/papr/energy_scale_info
+Date:		February 2022
+Contact:	Linux for PowerPC mailing list <[email protected]>
+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>
+Date:		February 2022
+Contact:	Linux for PowerPC mailing list <[email protected]>
+Description:	Energy, frequency attributes directory for POWERVM servers
+
+What:		/sys/firmware/papr/energy_scale_info/<id>/desc
+Date:		February 2022
+Contact:	Linux for PowerPC mailing list <[email protected]>
+Description:	String description of the energy attribute of <id>
+
+What:		/sys/firmware/papr/energy_scale_info/<id>/value
+Date:		February 2022
+Contact:	Linux for PowerPC mailing list <[email protected]>
+Description:	Numeric value of the energy attribute of <id>
+
+What:		/sys/firmware/papr/energy_scale_info/<id>/value_desc
+Date:		February 2022
+Contact:	Linux for PowerPC mailing list <[email protected]>
+Description:	String value of the energy attribute of <id>

arch/powerpc/include/asm/firmware.h

@@ -54,6 +54,7 @@
 #define FW_FEATURE_STUFF_TCE	ASM_CONST(0x0000008000000000)
 #define FW_FEATURE_RPT_INVALIDATE ASM_CONST(0x0000010000000000)
 #define FW_FEATURE_FORM2_AFFINITY ASM_CONST(0x0000020000000000)
+#define FW_FEATURE_ENERGY_SCALE_INFO ASM_CONST(0x0000040000000000)
 
 #ifndef __ASSEMBLY__
 
@@ -74,7 +75,8 @@ enum {
 		FW_FEATURE_HPT_RESIZE | FW_FEATURE_DRMEM_V2 |
 		FW_FEATURE_DRC_INFO | FW_FEATURE_BLOCK_REMOVE |
 		FW_FEATURE_PAPR_SCM | FW_FEATURE_ULTRAVISOR |
-		FW_FEATURE_RPT_INVALIDATE | FW_FEATURE_FORM2_AFFINITY,
+		FW_FEATURE_RPT_INVALIDATE | FW_FEATURE_FORM2_AFFINITY |
+		FW_FEATURE_ENERGY_SCALE_INFO,
 	FW_FEATURE_PSERIES_ALWAYS = 0,
 	FW_FEATURE_POWERNV_POSSIBLE = FW_FEATURE_OPAL | FW_FEATURE_ULTRAVISOR,
 	FW_FEATURE_POWERNV_ALWAYS = 0,

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)

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"}, \

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_KEXEC_CORE)	+= kexec.o
 obj-$(CONFIG_PSERIES_ENERGY)	+= pseries_energy.o

arch/powerpc/platforms/pseries/firmware.c

@@ -66,6 +66,7 @@ hypertas_fw_features_table[] = {
 	{FW_FEATURE_BLOCK_REMOVE,	"hcall-block-remove"},
 	{FW_FEATURE_PAPR_SCM,		"hcall-scm"},
 	{FW_FEATURE_RPT_INVALIDATE,	"hcall-rpt-invalidate"},
+	{FW_FEATURE_ENERGY_SCALE_INFO,	"hcall-energy-scale-info"},
 };
 
 /* Build up the firmware features bitmask using the contents of