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authorPratik R. Sampat <psampat@linux.ibm.com>2022-02-17 13:53:20 +0300
committerMichael Ellerman <mpe@ellerman.id.au>2022-03-07 16:05:00 +0300
commit3c14b73454cf9f6e2146443fdfbdfb912c0efed3 (patch)
tree5c29ed10af89390574941a6a3e7579a0e7682eb5 /Documentation/ABI
parentcc15ff3275694fedc33cd3d53212a43eec7aa0bc (diff)
downloadlinux-3c14b73454cf9f6e2146443fdfbdfb912c0efed3.tar.xz
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 <psampat@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220217105321.52941-2-psampat@linux.ibm.com
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+What: /sys/firmware/papr/energy_scale_info
+Date: February 2022
+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>
+Date: February 2022
+Contact: Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
+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 <linuxppc-dev@ozlabs.org>
+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 <linuxppc-dev@ozlabs.org>
+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 <linuxppc-dev@ozlabs.org>
+Description: String value of the energy attribute of <id>