Re: [PATCH v3 10/15] cpufreq/amd-pstate: Move limit updating code

[Mario Limonciello]

On 12/16/2024 08:16, Dhananjay Ugwekar wrote:
> Hello Mario,
>
> On 12/10/2024 12:22 AM, Mario Limonciello wrote:
> > The limit updating code in amd_pstate_epp_update_limit() should not
> > only apply to EPP updates.  Move it to amd_pstate_update_min_max_limit()
> > so other callers can benefit as well.
> >
> > With this move it's not necessary to have clamp_t calls anymore because
> > the verify callback is called when setting limits.
>
> While testing this series, I observed that with amd_pstate=passive + schedutil governor,
> the scaling_max_freq limits were not being honored and I bisected the issue down to this
> patch.
>
> I went through the code and noticed that in amd_pstate_adjust_perf(), we set the min_perf
> field in MSR_AMD_CPPC_REQ to "cap_perf" which is equal to cpudata->highest_perf (which is
> equal to 255 for non-preferred cores systems). This didnt seem logical to me and I changed
> cap_perf to cpudata->max_limit_perf which gives us the value updated in scaling_max_freq.
>
> I think as we removed the redundant clamping code, this pre-existing issue got exposed.
> The below diff fixes the issue for me.
>
> Please let me know your thoughts on this.
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index d7b1de97727a..1ac34e3f1fc5 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -699,7 +699,7 @@ static void amd_pstate_adjust_perf(unsigned int cpu,
>          if (min_perf < lowest_nonlinear_perf)
>                  min_perf = lowest_nonlinear_perf;
>
> -       max_perf = cap_perf;
> +       max_perf = cpudata->max_limit_perf;
>          if (max_perf < min_perf)
>                  max_perf = min_perf;

With this change I think you can also drop the comparison afterwards, as 
an optimization right?

As this is already in superm1.git/linux-next after testing can you 
please send a patch relative to superm1.git/linux-next branch?

Thanks!

> Thanks,
> Dhananjay
>
> > Reviewed-by: Gautham R. Shenoy <gautham.shenoy@xxxxxxx>
> > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> > ---
> > v2:
> >   * Drop lowest_perf variable
> > ---
> >   drivers/cpufreq/amd-pstate.c | 28 +++++-----------------------
> >   1 file changed, 5 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index 3a3df67c096d5..dc3c45b6f5103 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -537,10 +537,6 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
> >   	u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
> >   	u64 value = prev;
> >   
> > -	min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf,
> > -			cpudata->max_limit_perf);
> > -	max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf,
> > -			cpudata->max_limit_perf);
> >   	des_perf = clamp_t(unsigned long, des_perf, min_perf, max_perf);
> >   
> >   	max_freq = READ_ONCE(cpudata->max_limit_freq);
> > @@ -607,7 +603,7 @@ static int amd_pstate_verify(struct cpufreq_policy_data *policy_data)
> >   
> >   static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy)
> >   {
> > -	u32 max_limit_perf, min_limit_perf, lowest_perf, max_perf, max_freq;
> > +	u32 max_limit_perf, min_limit_perf, max_perf, max_freq;
> >   	struct amd_cpudata *cpudata = policy->driver_data;
> >   
> >   	max_perf = READ_ONCE(cpudata->highest_perf);
> > @@ -615,12 +611,8 @@ static int amd_pstate_update_min_max_limit(struct cpufreq_policy *policy)
> >   	max_limit_perf = div_u64(policy->max * max_perf, max_freq);
> >   	min_limit_perf = div_u64(policy->min * max_perf, max_freq);
> >   
> > -	lowest_perf = READ_ONCE(cpudata->lowest_perf);
> > -	if (min_limit_perf < lowest_perf)
> > -		min_limit_perf = lowest_perf;
> > -
> > -	if (max_limit_perf < min_limit_perf)
> > -		max_limit_perf = min_limit_perf;
> > +	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
> > +		min_limit_perf = min(cpudata->nominal_perf, max_limit_perf);
> >   
> >   	WRITE_ONCE(cpudata->max_limit_perf, max_limit_perf);
> >   	WRITE_ONCE(cpudata->min_limit_perf, min_limit_perf);
> > @@ -1562,28 +1554,18 @@ static void amd_pstate_epp_cpu_exit(struct cpufreq_policy *policy)
> >   static int amd_pstate_epp_update_limit(struct cpufreq_policy *policy)
> >   {
> >   	struct amd_cpudata *cpudata = policy->driver_data;
> > -	u32 max_perf, min_perf;
> >   	u64 value;
> >   	s16 epp;
> >   
> > -	max_perf = READ_ONCE(cpudata->highest_perf);
> > -	min_perf = READ_ONCE(cpudata->lowest_perf);
> >   	amd_pstate_update_min_max_limit(policy);
> >   
> > -	max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf,
> > -			cpudata->max_limit_perf);
> > -	min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf,
> > -			cpudata->max_limit_perf);
> >   	value = READ_ONCE(cpudata->cppc_req_cached);
> >   
> > -	if (cpudata->policy == CPUFREQ_POLICY_PERFORMANCE)
> > -		min_perf = min(cpudata->nominal_perf, max_perf);
> > -
> >   	value &= ~(AMD_CPPC_MAX_PERF_MASK | AMD_CPPC_MIN_PERF_MASK |
> >   		   AMD_CPPC_DES_PERF_MASK);
> > -	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, max_perf);
> > +	value |= FIELD_PREP(AMD_CPPC_MAX_PERF_MASK, cpudata->max_limit_perf);
> >   	value |= FIELD_PREP(AMD_CPPC_DES_PERF_MASK, 0);
> > -	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, min_perf);
> > +	value |= FIELD_PREP(AMD_CPPC_MIN_PERF_MASK, cpudata->min_limit_perf);
> >   
> >   	/* Get BIOS pre-defined epp value */
> >   	epp = amd_pstate_get_epp(cpudata, value);