[PATCH] ACPI: CPPC: Skip writes to unsupported performance controls

[Christian Loehle]

MIN_PERF and MAX_PERF are optional CPPC controls. DESIRED_PERF is also
optional with CPPC2 when autonomous selection is supported.

The cppc-cpufreq target callbacks populate both limits for every request
without checking whether the controls are implemented. cppc_set_perf()
consequently passes NULL register descriptors to cpc_write(). The writes
fail width validation and their return values are ignored, so the failed
access paths are repeated on every target request. An autonomous-only
platform can take the same path for DESIRED_PERF.

Check that each performance control is supported before calling
cpc_write().

Fixes: ea3db45ae476 ("cpufreq: cppc: Update MIN_PERF/MAX_PERF in target callbacks")
Reviewed-by: Sumit Gupta <sumitg@xxxxxxxxxx>
Signed-off-by: Christian Loehle <christian.loehle@xxxxxxx>
---
v2: Also added desired_perf check (Sumit)

 drivers/acpi/cppc_acpi.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/cppc_acpi.c b/drivers/acpi/cppc_acpi.c
index 1d3a94100491..53d09ca98f06 100644
--- a/drivers/acpi/cppc_acpi.c
+++ b/drivers/acpi/cppc_acpi.c
@@ -1963,16 +1963,17 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
 		cpc_desc->write_cmd_status = 0;
 	}
 
-	cpc_write(cpu, desired_reg, perf_ctrls->desired_perf);
+	if (CPC_SUPPORTED(desired_reg))
+		cpc_write(cpu, desired_reg, perf_ctrls->desired_perf);
 
 	/*
 	 * Only write if min_perf and max_perf not zero. Some drivers pass zero
 	 * value to min and max perf, but they don't mean to set the zero value,
 	 * they just don't want to write to those registers.
 	 */
-	if (perf_ctrls->min_perf)
+	if (perf_ctrls->min_perf && CPC_SUPPORTED(min_perf_reg))
 		cpc_write(cpu, min_perf_reg, perf_ctrls->min_perf);
-	if (perf_ctrls->max_perf)
+	if (perf_ctrls->max_perf && CPC_SUPPORTED(max_perf_reg))
 		cpc_write(cpu, max_perf_reg, perf_ctrls->max_perf);
 
 	if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg))
-- 
2.34.1