linux-kernel - [PATCH v5 6/6] Documentation: amd_pstate: Update amd

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Date:   Wed, 1 Feb 2023 06:58:23 +0000
From:   Wyes Karny <wyes.karny@....com>
To:     Rafael J Wysocki <rafael@...nel.org>,
        Huang Rui <ray.huang@....com>,
        Jonathan Corbet <corbet@....net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        <Mario.Limonciello@....com>, <Perry.Yuan@....com>
CC:     <linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-pm@...r.kernel.org>, Bagas Sanjaya <bagasdotme@...il.com>,
        <santosh.shukla@....com>, Len Brown <lenb@...nel.org>,
        Robert Moore <robert.moore@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Ananth Narayan <ananth.narayan@....com>,
        <gautham.shenoy@....com>, Tor Vic <torvic9@...lbox.org>,
        Wyes Karny <wyes.karny@....com>,
        Mario Limonciello <mario.limonciello@....com>
Subject: [PATCH v5 6/6] Documentation: amd_pstate: Update amd_pstate status sysfs for guided

Update amd_pstate status sysfs for guided mode.

Signed-off-by: Wyes Karny <wyes.karny@....com>
Reviewed-by: Bagas Sanjaya <bagasdotme@...il.com>
Reviewed-by: Mario Limonciello <mario.limonciello@....com>
---
 Documentation/admin-guide/pm/amd-pstate.rst | 34 ++++++++++++++++-----
 1 file changed, 27 insertions(+), 7 deletions(-)

diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index 5304adf2fc2f..17fafe5d6625 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -303,13 +303,18 @@ efficiency frequency management method on AMD processors.
 AMD Pstate Driver Operation Modes
 =================================
 
-``amd_pstate`` CPPC has two operation modes: CPPC Autonomous(active) mode and
-CPPC non-autonomous(passive) mode.
-active mode and passive mode can be chosen by different kernel parameters.
-When in Autonomous mode, CPPC ignores requests done in the Desired Performance
-Target register and takes into account only the values set to the Minimum requested
-performance, Maximum requested performance, and Energy Performance Preference
-registers. When Autonomous is disabled, it only considers the Desired Performance Target.
+``amd_pstate`` CPPC has 3 operation modes: autonomous (active) mode,
+non-autonomous (passive) mode and guided autonomous (guided) mode.
+Active/passive/guided mode can be chosen by different kernel parameters.
+
+- In autonomous mode, platform ignores the desired performance level request
+  and takes into account only the values set to the minimum, maximum and energy
+  performance preference registers.
+- In non-autonomous mode, platform gets desired performance level
+  from OS directly through Desired Performance Register.
+- In guided-autonomous mode, platform sets operating performance level
+  autonomously according to the current workload and within the limits set by
+  OS through min and max performance registers.
 
 Active Mode
 ------------
@@ -338,6 +343,15 @@ to the Performance Reduction Tolerance register. Above the nominal performance l
 processor must provide at least nominal performance requested and go higher if current
 operating conditions allow.
 
+Guided Mode
+-----------
+
+``amd_pstate=guided``
+
+If ``amd_pstate=guided`` is passed to kernel command line option then this mode
+is activated.  In this mode, driver requests minimum and maximum performance
+level and the platform autonomously selects a performance level in this range
+and appropriate to the current workload.
 
 User Space Interface in ``sysfs``
 =================================
@@ -358,6 +372,9 @@ control its functionality at the system level.  They are located in the
 	"passive"
 		The driver is functional and in the ``passive mode``
 
+	"guided"
+		The driver is functional and in the ``guided mode``
+
 	"disable"
 		The driver is unregistered and not functional now.
 
@@ -368,6 +385,9 @@ control its functionality at the system level.  They are located in the
         to the operation mode represented by that string - or to be
         unregistered in the "disable" case.
 
+Note: If someone tries to change the state to same state, which is currently
+active in the driver, then this will return -EBUSY error.
+
 ``cpupower`` tool support for ``amd-pstate``
 ===============================================
 
-- 
2.34.1