From mboxrd@z Thu Jan 1 00:00:00 1970 From: Fabiano Rosas Date: Fri, 23 Jul 2021 13:16:32 +0000 Subject: Re: [PATCH v7 1/1] powerpc/pseries: Interface to represent PAPR firmware attributes Message-Id: <87r1fpcgr3.fsf@linux.ibm.com> List-Id: References: <20210723054609.15033-1-psampat@linux.ibm.com> <20210723054609.15033-2-psampat@linux.ibm.com> In-Reply-To: <20210723054609.15033-2-psampat@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Pratik R. Sampat" , mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, kjain@linux.ibm.com, linuxppc-dev@lists.ozlabs.org, kvm-ppc@vger.kernel.org, linux-kernel@vger.kernel.org, psampat@linux.ibm.com, pratik.r.sampat@gmail.com "Pratik R. Sampat" writes: > 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/ > |-- / > |-- desc > |-- value > |-- value_desc (if exists) > |-- / > |-- 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 > Reviewed-by: Gautham R. Shenoy Reviewed-by: Fabiano Rosas