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authorWyes Karny <wyes.karny@amd.com>2023-02-14 10:58:11 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2023-02-15 17:58:07 +0300
commit6e9d12125fcac048c78f497044370c1da85b552a (patch)
tree3c61b07dcb2c764bed609f3189d1679009278845 /drivers/cpufreq
parentf0f8e9e730b84dd9255343dc6b2cbd6ecc3a08e0 (diff)
downloadlinux-6e9d12125fcac048c78f497044370c1da85b552a.tar.xz
cpufreq: amd-pstate: Fix invalid write to MSR_AMD_CPPC_REQ
`amd_pstate_set_epp` function uses `cppc_req_cached` and `epp` variable to update the MSR_AMD_CPPC_REQ register for AMD MSR systems. The recent commit 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized variable use") changed the sequence of updating cppc_req_cached and writing the MSR_AMD_CPPC_REQ. Therefore while switching from powersave to performance governor and vice-versa in active mode MSR_AMD_CPPC_REQ is set with the previous cached value. To fix this: first update the `cppc_req_cached` variable and then call `amd_pstate_set_epp` function. - Before commit 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized variable use"): With powersave governor: [ 1.652743] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff [ 1.652744] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff [ 1.652746] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0 Changing to performance governor: [ 300.493842] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff [ 300.493846] amd_pstate_set_epp: writing cppc_req_cached = 0xffff [ 300.493847] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0 - After commit 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized variable use"): With powersave governor: [ 1.646037] amd_pstate_set_epp: writing cppc_req_cached = 0xffff [ 1.646038] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0 [ 1.646042] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff Changing to performance governor: [ 687.117401] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff [ 687.117405] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0 [ 687.117419] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff - After this fix: With powersave governor: [ 2.525717] amd_pstate_epp_init: writing to cppc_req_cached = 0x1eff [ 2.525720] amd_pstate_set_epp: writing cppc_req_cached = 0x1eff [ 2.525722] amd_pstate_set_epp: writing min_perf = 30, des_perf = 0, max_perf = 255, epp = 0 Changing to performance governor: [ 3440.152468] amd_pstate_epp_init: writing to cppc_req_cached = 0xffff [ 3440.152473] amd_pstate_set_epp: writing cppc_req_cached = 0xffff [ 3440.152474] amd_pstate_set_epp: writing min_perf = 255, des_perf = 0, max_perf = 255, epp = 0 Fixes: 7cca9a9851a5 ("cpufreq: amd-pstate: avoid uninitialized variable use") Signed-off-by: Wyes Karny <wyes.karny@amd.com> Acked-by: Huang Rui <ray.huang@amd.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/amd-pstate.c25
1 files changed, 13 insertions, 12 deletions
diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
index b8862afef4e4..45c88894fd8e 100644
--- a/drivers/cpufreq/amd-pstate.c
+++ b/drivers/cpufreq/amd-pstate.c
@@ -1057,27 +1057,28 @@ static void amd_pstate_epp_init(unsigned int cpu)
cpudata->epp_policy = cpudata->policy;
- if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE) {
- epp = amd_pstate_get_epp(cpudata, value);
- if (epp < 0)
- goto skip_epp;
- /* force the epp value to be zero for performance policy */
- epp = 0;
- } else {
- /* Get BIOS pre-defined epp value */
- epp = amd_pstate_get_epp(cpudata, value);
- if (epp)
- goto skip_epp;
+ /* Get BIOS pre-defined epp value */
+ epp = amd_pstate_get_epp(cpudata, value);
+ if (epp < 0) {
+ /**
+ * This return value can only be negative for shared_memory
+ * systems where EPP register read/write not supported.
+ */
+ goto skip_epp;
}
+
+ if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
+ epp = 0;
+
/* Set initial EPP value */
if (boot_cpu_has(X86_FEATURE_CPPC)) {
value &= ~GENMASK_ULL(31, 24);
value |= (u64)epp << 24;
}
+ WRITE_ONCE(cpudata->cppc_req_cached, value);
amd_pstate_set_epp(cpudata, epp);
skip_epp:
- WRITE_ONCE(cpudata->cppc_req_cached, value);
cpufreq_cpu_put(policy);
}