Hi, On Thursday 12 Sep 2024 at 15:22:29 (+0800), Jie Zhan wrote: > The CPPC performance feedback counters could return 0 when the target cpu > is in a deep idle state, e.g. powered off, and those counters are not > powered. In this case, cppc_cpufreq_get_rate() returns 0, and hence, > cpufreq_online() gets a false error and doesn't generate a cpufreq policy, > which happens in cpufreq_add_dev() when a new cpu device is added. > > Don't take it as an error and return the frequency corresponding to the > desired perf when the feedback counters are 0. > > Fixes: 6a4fec4f6d30 ("cpufreq: cppc: cppc_cpufreq_get_rate() returns zero in all error cases.") > Signed-off-by: Jie Zhan <zhanjie9@xxxxxxxxxxxxx> > Reviewed-by: Zeng Heng <zengheng4@xxxxxxxxxx> > --- > drivers/cpufreq/cppc_cpufreq.c | 19 +++++++++++++++++-- > 1 file changed, 17 insertions(+), 2 deletions(-) > > diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c > index bafa32dd375d..6aa3af56924b 100644 > --- a/drivers/cpufreq/cppc_cpufreq.c > +++ b/drivers/cpufreq/cppc_cpufreq.c > @@ -748,18 +748,33 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu) > > ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t0); > if (ret) > - return 0; > + goto out_err; > > udelay(2); /* 2usec delay between sampling */ > > ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t1); > if (ret) > - return 0; > + goto out_err; > > delivered_perf = cppc_perf_from_fbctrs(cpu_data, &fb_ctrs_t0, > &fb_ctrs_t1); > > return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf); > + > +out_err: > + /* > + * Feedback counters could be 0 when cores are powered down. > + * Take desired perf for reflecting frequency in this case. > + */ > + if (ret == -EFAULT) { > + ret = cppc_get_desired_perf(cpu, &delivered_perf); > + if (ret) > + return 0; > + > + return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf); > + } > + > + return 0; > } A possible (slimmer) alternative implementation for you to consider (this merges patches 1 & 2): diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c index bafa32dd375d..c16be9651a6f 100644 --- a/drivers/cpufreq/cppc_cpufreq.c +++ b/drivers/cpufreq/cppc_cpufreq.c @@ -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) + perf = cpu_data->perf_ctrls.desired_perf; + cppc_fi->prev_perf_fb_ctrs = fb_ctrs; perf <<= SCHED_CAPACITY_SHIFT; @@ -726,7 +729,7 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data, /* Check to avoid divide-by zero and invalid delivered_perf */ if (!delta_reference || !delta_delivered) - return cpu_data->perf_ctrls.desired_perf; + return 0; return (reference_perf * delta_delivered) / delta_reference; } @@ -736,7 +739,7 @@ static unsigned int cppc_cpufreq_get_rate(unsigned int cpu) struct cppc_perf_fb_ctrs fb_ctrs_t0 = {0}, fb_ctrs_t1 = {0}; struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); struct cppc_cpudata *cpu_data; - u64 delivered_perf; + u64 delivered_perf = 0; int ret; if (!policy) @@ -747,19 +750,22 @@ 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; + if (!ret) { + udelay(2); /* 2usec delay between sampling */ + ret = cppc_get_perf_ctrs(cpu, &fb_ctrs_t1); + } + if (!ret) + delivered_perf = cppc_perf_from_fbctrs(cpu_data, &fb_ctrs_t0, + &fb_ctrs_t1); + if ((ret == -EFAULT) || !delivered_perf) { + if (cppc_get_desired_perf(cpu, &delivered_perf)) + delivered_perf = cpu_data->perf_ctrls.desired_perf; + } - delivered_perf = cppc_perf_from_fbctrs(cpu_data, &fb_ctrs_t0, - &fb_ctrs_t1); + if (delivered_perf) + return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf); - return cppc_perf_to_khz(&cpu_data->perf_caps, delivered_perf); + return 0; } disclaimer: not fully checked so likely not "production ready" code :) Hope it helps, Ionela. > > static int cppc_cpufreq_set_boost(struct cpufreq_policy *policy, int state) > -- > 2.33.0 >