cpufreq/amd-pstate: add kernel command line to override dynamic epp

Add `amd_dynamic_epp=enable` and `amd_dynamic_epp=disable` to override
the kernel configuration option `CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP`
locally.

Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>

Author: superm1

Documentation/admin-guide/kernel-parameters.txt

@@ -493,6 +493,13 @@ Kernel parameters
 			disable
 			  Disable amd-pstate preferred core.
 
+	amd_dynamic_epp=
+			[X86]
+			disable
+			  Disable amd-pstate dynamic EPP.
+			enable
+			  Enable amd-pstate dynamic EPP.
+
 	amijoy.map=	[HW,JOY] Amiga joystick support
 			Map of devices attached to JOY0DAT and JOY1DAT
 			Format: <a>,<b>

Documentation/admin-guide/pm/amd-pstate.rst

@@ -474,6 +474,13 @@ For systems that support ``amd-pstate`` preferred core, the core rankings will
 always be advertised by the platform. But OS can choose to ignore that via the
 kernel parameter ``amd_prefcore=disable``.
 
+``amd_dynamic_epp``
+
+When AMD pstate is in auto mode, dynamic EPP will control whether the kernel
+autonomously changes the EPP mode. The default is configured by
+``CONFIG_X86_AMD_PSTATE_DYNAMIC_EPP`` but can be explicitly enabled with
+``amd_dynamic_epp=enable`` or disabled with ``amd_dynamic_epp=disable``.
+
 User Space Interface in ``sysfs`` - General
 ===========================================
 

drivers/cpufreq/amd-pstate.c

@@ -2227,8 +2227,19 @@ static int __init amd_prefcore_param(char *str)
 	return 0;
 }
 
+static int __init amd_dynamic_epp_param(char *str)
+{
+	if (!strcmp(str, "disable"))
+		dynamic_epp = false;
+	if (!strcmp(str, "enable"))
+		dynamic_epp = true;
+
+	return 0;
+}
+
 early_param("amd_pstate", amd_pstate_param);
 early_param("amd_prefcore", amd_prefcore_param);
+early_param("amd_dynamic_epp", amd_dynamic_epp_param);
 
 MODULE_AUTHOR("Huang Rui <ray.huang@amd.com>");
 MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");