Re: [PATCH 1/2] cpufreq/amd-pstate: Add an early param to disable MSR mode
From: Mario Limonciello
Date: Tue Sep 03 2024 - 09:14:40 EST
On 9/1/2024 00:00, Mario Limonciello wrote:
From: Mario Limonciello <mario.limonciello@xxxxxxx>
This lets a system that supports the MSR run in shared memory mode
instead to help replicate and debug issues.
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
After some offline discussion, will drop this patch. Second patch will
remain and I will queue it up for -next.
---
.../admin-guide/kernel-parameters.txt | 5 +++
Documentation/admin-guide/pm/amd-pstate.rst | 5 +++
drivers/cpufreq/amd-pstate.c | 32 +++++++++++++------
3 files changed, 32 insertions(+), 10 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 09126bb8cc9ff..041c609ed50ea 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -383,6 +383,11 @@
disable
Disable amd-pstate preferred core.
+ amd_pstate_msr=
+ [X86]
+ disable
+ Disable amd-pstate CPPC MSR (force shared memory).
+
amijoy.map= [HW,JOY] Amiga joystick support
Map of devices attached to JOY0DAT and JOY1DAT
Format: <a>,<b>
diff --git a/Documentation/admin-guide/pm/amd-pstate.rst b/Documentation/admin-guide/pm/amd-pstate.rst
index d0324d44f5482..b06632556102e 100644
--- a/Documentation/admin-guide/pm/amd-pstate.rst
+++ b/Documentation/admin-guide/pm/amd-pstate.rst
@@ -411,6 +411,11 @@ 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_pstate_msr=disable``
+
+For systems that support a dedicated CPPC MSR, ignore it's use and run
+with shared memory instead.
+
User Space Interface in ``sysfs`` - General
===========================================
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index 93adde45bebce..89438a3654002 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -88,6 +88,7 @@ static struct cpufreq_driver amd_pstate_epp_driver;
static int cppc_state = AMD_PSTATE_UNDEFINED;
static bool cppc_enabled;
static bool amd_pstate_prefcore = true;
+static bool amd_pstate_msr = true;
static struct quirk_entry *quirks;
/*
@@ -187,7 +188,7 @@ static s16 amd_pstate_get_epp(struct amd_cpudata *cpudata, u64 cppc_req_cached)
u64 epp;
int ret;
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
if (!cppc_req_cached) {
epp = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ,
&cppc_req_cached);
@@ -260,7 +261,7 @@ static int amd_pstate_set_epp(struct amd_cpudata *cpudata, u32 epp)
int ret;
struct cppc_perf_ctrls perf_ctrls;
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
u64 value = READ_ONCE(cpudata->cppc_req_cached);
value &= ~GENMASK_ULL(31, 24);
@@ -813,7 +814,7 @@ static int amd_pstate_get_highest_perf(int cpu, u32 *highest_perf)
{
int ret;
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
u64 cap1;
ret = rdmsrl_safe_on_cpu(cpu, MSR_AMD_CPPC_CAP1, &cap1);
@@ -1058,7 +1059,7 @@ static int amd_pstate_cpu_init(struct cpufreq_policy *policy)
/* It will be updated by governor */
policy->cur = policy->cpuinfo.min_freq;
- if (cpu_feature_enabled(X86_FEATURE_CPPC))
+ if (amd_pstate_msr)
policy->fast_switch_possible = true;
ret = freq_qos_add_request(&policy->constraints, &cpudata->req[0],
@@ -1288,7 +1289,7 @@ static int amd_pstate_change_mode_without_dvr_change(int mode)
cppc_state = mode;
- if (cpu_feature_enabled(X86_FEATURE_CPPC) || cppc_state == AMD_PSTATE_ACTIVE)
+ if (amd_pstate_msr || cppc_state == AMD_PSTATE_ACTIVE)
return 0;
for_each_present_cpu(cpu) {
@@ -1524,7 +1525,7 @@ static int amd_pstate_epp_cpu_init(struct cpufreq_policy *policy)
else
policy->policy = CPUFREQ_POLICY_POWERSAVE;
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
ret = rdmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, &value);
if (ret)
return ret;
@@ -1612,7 +1613,7 @@ static void amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
epp = 0;
/* Set initial EPP value */
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
value &= ~GENMASK_ULL(31, 24);
value |= (u64)epp << 24;
}
@@ -1657,7 +1658,7 @@ static void amd_pstate_epp_reenable(struct amd_cpudata *cpudata)
value = READ_ONCE(cpudata->cppc_req_cached);
max_perf = READ_ONCE(cpudata->highest_perf);
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
} else {
perf_ctrls.max_perf = max_perf;
@@ -1691,7 +1692,7 @@ static void amd_pstate_epp_offline(struct cpufreq_policy *policy)
value = READ_ONCE(cpudata->cppc_req_cached);
mutex_lock(&amd_pstate_limits_lock);
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr) {
cpudata->epp_policy = CPUFREQ_POLICY_UNKNOWN;
/* Set max perf same as min perf */
@@ -1936,7 +1937,9 @@ static int __init amd_pstate_init(void)
}
/* capability check */
- if (cpu_feature_enabled(X86_FEATURE_CPPC)) {
+ if (amd_pstate_msr)
+ amd_pstate_msr = cpu_feature_enabled(X86_FEATURE_CPPC);
+ if (amd_pstate_msr) {
pr_debug("AMD CPPC MSR based functionality is supported\n");
if (cppc_state != AMD_PSTATE_ACTIVE)
current_pstate_driver->adjust_perf = amd_pstate_adjust_perf;
@@ -2002,8 +2005,17 @@ static int __init amd_prefcore_param(char *str)
return 0;
}
+static int __init amd_msr_param(char *str)
+{
+ if (!strcmp(str, "disable"))
+ amd_pstate_msr = false;
+
+ return 0;
+}
+
early_param("amd_pstate", amd_pstate_param);
early_param("amd_prefcore", amd_prefcore_param);
+early_param("amd_pstate_msr", amd_msr_param);
MODULE_AUTHOR("Huang Rui <ray.huang@xxxxxxx>");
MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");