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ACPI: CPPC: Evaluate performance-control PCC use once

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cppc_set_perf() evaluates the same immutable address-space predicates
before and after each phase of a performance-control update. This repeats
the three-control PCC test three times for every target request.

Evaluate the predicate once after resolving the control descriptors and
reuse the result throughout the transaction.

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20260803210527.1285229-4-christian.loehle@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Christian Loehle 2026-08-03 22:05:27 +01:00 committed by Rafael J. Wysocki
parent 9c5ab33a6d
commit b0f51f98fb
1 changed files with 6 additions and 3 deletions
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9
drivers/acpi/cppc_acpi.c
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@ -2012,6 +2012,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
struct cpc_register_resource *desired_reg, *min_perf_reg, *max_perf_reg;
int pcc_ss_id = per_cpu(cpu_pcc_subspace_idx, cpu);
struct cppc_pcc_data *pcc_ss_data = NULL;
bool regs_in_pcc;
int ret = 0;
if (!cpc_desc) {
@ -2022,6 +2023,8 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
desired_reg = &cpc_desc->cpc_regs[DESIRED_PERF];
min_perf_reg = &cpc_desc->cpc_regs[MIN_PERF];
max_perf_reg = &cpc_desc->cpc_regs[MAX_PERF];
regs_in_pcc = CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) ||
CPC_IN_PCC(max_perf_reg);
/*
* This is Phase-I where we want to write to CPC registers
@ -2030,7 +2033,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
* Since read_lock can be acquired by multiple CPUs simultaneously we
* achieve that goal here
*/
if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg)) {
if (regs_in_pcc) {
if (pcc_ss_id < 0) {
pr_debug("Invalid pcc_ss_id\n");
return -ENODEV;
@ -2066,7 +2069,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
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))
if (regs_in_pcc)
up_read(&pcc_ss_data->pcc_lock); /* END Phase-I */
/*
* This is Phase-II where we transfer the ownership of PCC to Platform
@ -2114,7 +2117,7 @@ int cppc_set_perf(int cpu, struct cppc_perf_ctrls *perf_ctrls)
* case during a CMD_READ and if there are pending writes it delivers
* the write command before servicing the read command
*/
if (CPC_IN_PCC(desired_reg) || CPC_IN_PCC(min_perf_reg) || CPC_IN_PCC(max_perf_reg)) {
if (regs_in_pcc) {
if (down_write_trylock(&pcc_ss_data->pcc_lock)) {/* BEGIN Phase-II */
/* Update only if there are pending write commands */
if (pcc_ss_data->pending_pcc_write_cmd)