在 2024/9/26 10:57, Jie Zhan 写道:
On 25/09/2024 17:28, lihuisong (C) wrote:
Hi Jie,
LGTM except for some trivial,
Reviewed-by: Huisong Li <lihuisong@xxxxxxxxxx>
Thanks.
在 2024/9/19 16:45, Jie Zhan 写道:
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
to reflect the frequency; if failed, return the cached desired perf.
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>
Reviewed-by: Ionela Voinescu <ionela.voinescu@xxxxxxx>
---
drivers/cpufreq/cppc_cpufreq.c | 49 +++++++++++++++++++++++++++-------
1 file changed, 39 insertions(+), 10 deletions(-)
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index bafa32dd375d..e55192303a9f 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)
+ return;
+
cppc_fi->prev_perf_fb_ctrs = fb_ctrs;
perf <<= SCHED_CAPACITY_SHIFT;
@@ -726,11 +729,26 @@ static int cppc_perf_from_fbctrs(struct cppc_cpudata *cpu_data,
/* Check to avoid divide-by zero and invalid delivered_perf */
Now this comment can be removed, right?
Didn't notice this comment, but, having a check, I think it still fits.
'!delta_reference' avoids divide-by zero, and '!delta_delivered' checks
invalid delivered_perf.
The comment "avoid divide-by zero" is just for the below code:
"(reference_perf * delta_delivered) / delta_reference".
So It is also useful, but I think It's obvious and it doesn't make much
sense.
The comment "avoid invalid delivered_perf" is for the return value.
Now this func return zero which can't count as a valid delivered_perf,
right?
So I think we just leave it unchanged.
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};
@@ -746,18 +764,29 @@ 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)
+ goto out_invalid_counters;
suggest that add some comments for ret == -EFAULT case.
Because this error code depands on the implementation of cppc_get_perf_ctrs.
If add a new exception case which also return -EFAULT, then this switch is unreasonable.
Sure. What about adding the following comment:
/* -EFAULT indicates that any of the associated CPPC regs is 0. */
Ack
.
