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cppc_cpufreq: Use desired perf if feedback ctrs are 0 or unchanged

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BugLink: https://bugs.launchpad.net/bugs/2101915

[ Upstream commit c47195631960b626058c335aec31f186fa854f97 ]

The CPPC performance feedback counters could be 0 or unchanged when the
target cpu is in a low-power idle state, e.g. power-gated or clock-gated.

When the counters are 0, cppc_cpufreq_get_rate() returns 0 KHz, which makes
cpufreq_online() get a false error and fail to generate a cpufreq policy.

When the counters are unchanged, the existing cppc_perf_from_fbctrs()
returns a cached desired perf, but some platforms may update the real
frequency back to the desired perf reg.

For the above cases in cppc_cpufreq_get_rate(), get the latest desired perf
from the CPPC reg to reflect the frequency because some platforms may
update the actual frequency back there; if failed, use the cached desired
perf.

Fixes: 6a4fec4f6d ("cpufreq: cppc: cppc_cpufreq_get_rate() returns zero in all error cases.")
Signed-off-by: Jie Zhan <zhanjie9@hisilicon.com>
Reviewed-by: Zeng Heng <zengheng4@huawei.com>
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Reviewed-by: Huisong Li <lihuisong@huawei.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
This commit is contained in:
Jie Zhan
2025-03-11 08:51:19 +09:00
committed by Stefan Bader
parent 22f44214ee
commit 62a22b36eb
1 changed files with 46 additions and 11 deletions
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drivers/cpufreq/cppc_cpufreq.c
+46 -11
View File
@@ -118,6 +118,9 @@ static void cppc_scale_freq_workfn(struct kthread_work *work)
perf = cppc_perf_from_fbctrs(cpu_data, &cppc_fi->prev_perf_fb_ctrs,
&fb_ctrs);
if (!perf)
return;
cppc_fi->prev_perf_fb_ctrs = fb_ctrs;
perf <<= SCHED_CAPACITY_SHIFT;
@@ -730,13 +733,31 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data,
delta_delivered = get_delta(fb_ctrs_t1->delivered,
fb_ctrs_t0->delivered);
/* Check to avoid divide-by zero and invalid delivered_perf */
/*
* Avoid divide-by zero and unchanged feedback counters.
* Leave it for callers to handle.
*/
if (!delta_reference || !delta_delivered)
return cpu_data->perf_ctrls.desired_perf;
return 0;
return (reference_perf * delta_delivered) / delta_reference;
}
static int cppc_get_perf_ctrs_sample(int cpu,
struct cppc_perf_fb_ctrs *fb_ctrs_t0,
struct cppc_perf_fb_ctrs *fb_ctrs_t1)
{
int ret;
ret = cppc_get_perf_ctrs(cpu, fb_ctrs_t0);
if (ret)
return ret;
udelay(2); /* 2usec delay between sampling */
return cppc_get_perf_ctrs(cpu, fb_ctrs_t1);
}
static unsigned int cppc_cpufreq_get_rate(unsigned int cpu)
{
struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0};
@@ -752,18 +773,32 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu)
cpufreq_cpu_put(policy);
ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0);
if (ret)
return 0;
udelay(2); /* 2usec delay between sampling */
ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t1);
if (ret)
return 0;
ret = cppc_get_perf_ctrs_sample(cpu, &fb_ctrs_t0, &fb_ctrs_t1);
if (ret) {
if (ret == -EFAULT)
/* Any of the associated CPPC regs is 0. */
goto out_invalid_counters;
else
return 0;
}
delivered_perf = cppc_perf_from_fbctrs(cpu_data, &fb_ctrs_t0,
&fb_ctrs_t1);
if (!delivered_perf)
goto out_invalid_counters;
return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf);
out_invalid_counters:
/*
* Feedback counters could be unchanged or 0 when a cpu enters a
* low-power idle state, e.g. clock-gated or power-gated.
* Use desired perf for reflecting frequency. Get the latest register
* value first as some platforms may update the actual delivered perf
* there; if failed, resort to the cached desired perf.
*/
if (cppc_get_desired_perf(cpu, &delivered_perf))
delivered_perf = cpu_data->perf_ctrls.desired_perf;
return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf);
}