platform/x86/amd: amd_3d_vcache: Add sysfs ABI documentation

Add documentation for the amd_3d_vcache sysfs bus platform driver
interface so that userspace applications can use it to change mode
preferences, either frequency or cache.

Co-developed-by: Perry Yuan <perry.yuan@amd.com>
Signed-off-by: Perry Yuan <perry.yuan@amd.com>
Co-developed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
Link: https://lore.kernel.org/r/20241112170307.3745777-3-Basavaraj.Natikar@amd.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

Author: basuamd

Documentation/ABI/testing/sysfs-bus-platform-drivers-amd_x3d_vcache

@@ -0,0 +1,12 @@
+What:		/sys/bus/platform/drivers/amd_x3d_vcache/AMDI0101:00/amd_x3d_mode
+Date:		November 2024
+KernelVersion:	6.13
+Contact:	Basavaraj Natikar <Basavaraj.Natikar@amd.com>
+Description:	(RW) AMD 3D V-Cache optimizer allows users to switch CPU core
+		rankings dynamically.
+
+		This file switches between these two modes:
+		- "frequency" cores within the faster CCD are prioritized before
+		those in the slower CCD.
+		- "cache" cores within the larger L3 CCD are prioritized before
+		those in the smaller L3 CCD.

MAINTAINERS

@@ -978,6 +978,7 @@ M:	Basavaraj Natikar <Basavaraj.Natikar@amd.com>
 R:	Mario Limonciello <mario.limonciello@amd.com>
 L:	platform-driver-x86@vger.kernel.org
 S:	Supported
+F:	Documentation/ABI/testing/sysfs-bus-platform-drivers-amd_x3d_vcache
 F:	drivers/platform/x86/amd/x3d_vcache.c
 
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