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| author | Christian Loehle <christian.loehle@arm.com> | 2026-08-03 21:35:30 +0100 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2026-08-05 14:59:01 +0200 |
| commit | d3576424e8fa702a15a1963718a07eb672db9be7 (patch) | |
| tree | fc770075dbc6531e2f5c2907c2ad2f7b80078fdb | |
| parent | df5a1d4a8cdfda20eb2581a85e81c7d436866534 (diff) | |
| download | linux-d3576424e8fa702a15a1963718a07eb672db9be7.tar.gz linux-d3576424e8fa702a15a1963718a07eb672db9be7.zip | |
ACPI: CPPC: Skip desired_perf read in cppc_get_perf()
ACPI 6.5 defines _CPC revision 3 and lists Read/Write as the Optional
Attribute of Desired Performance. ACPI 6.6 advances _CPC to revision 4 and
lists only Write. cppc_get_perf() nevertheless reads the register when
initializing performance controls, even though cppc-cpufreq overwrites the
value before using it.
Use the _CPC revision check from cppc_get_desired_perf() and leave
desired_perf zero instead of reading it for _CPC revision 4 or later. Also
exclude the register from PCC read-command detection so it cannot trigger
an otherwise unnecessary read command.
Fixes: 658fa7b1c47a ("ACPI: CPPC: Add cppc_get_perf() API to read performance controls")
Cc: stable@vger.kernel.org
Suggested-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Reviewed-by: Zhongqiu Han <zhongqiu.han@oss.qualcomm.com>
Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260803203531.1268651-3-christian.loehle@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | drivers/acpi/cppc_acpi.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c index 42aeb749ebe0..becb7e442b30 100644 --- a/drivers/acpi/cppc_acpi.c +++ b/drivers/acpi/cppc_acpi.c @@ -1845,12 +1845,14 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) u64 desired_perf = 0, min = 0, max = 0, energy_perf = 0, auto_sel = 0; int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu); struct cppc_pcc_data *pcc_ss_data = NULL; + bool read_desired_perf; int ret = 0, regs_in_pcc = 0; if (!cpc_desc) { pr_debug("No CPC descriptor for CPU:%d\n", cpu); return -ENODEV; } + read_desired_perf = cppc_desired_perf_readable(cpc_desc); if (!perf_ctrls) { pr_debug("Invalid perf_ctrls pointer\n"); @@ -1864,7 +1866,8 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) auto_sel_reg = &cpc_desc->cpc_regs[AUTO_SEL_ENABLE]; /* Are any of the regs PCC ?*/ - if (CPC_IN_PCC(desired_perf_reg) || CPC_IN_PCC(min_perf_reg) || + if ((read_desired_perf && CPC_IN_PCC(desired_perf_reg)) || + CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg) || CPC_IN_PCC(energy_perf_reg) || CPC_IN_PCC(auto_sel_reg)) { if (pcc_ss_id < 0) { @@ -1896,7 +1899,7 @@ int cppc_get_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls) } perf_ctrls->min_perf = min; - if (CPC_SUPPORTED(desired_perf_reg)) { + if (read_desired_perf && CPC_SUPPORTED(desired_perf_reg)) { ret = cpc_read(cpu, desired_perf_reg, &desired_perf); if (ret) goto out_err; |