Re: [PATCH] x86, sched: Fix the AMD CPPC maximum perf on some specific generations

[Huang Rui]

On Tue, Apr 20, 2021 at 04:22:31PM +0800, Borislav Petkov wrote:
> On Tue, Apr 20, 2021 at 04:09:43PM +0800, Huang Rui wrote:
> > Some AMD Ryzen generations has different calculation method on maximum
> > perf. 255 is not for all asics, some specific generations used 166 as
> > the maximum perf. This patch is to fix the different maximum perf value
> 
> Avoid having "This patch" or "This commit" in the commit message. It is
> tautologically useless.
> 
> Also, do
> 
> $ git grep 'This patch' Documentation/process
> 
> for more details.

Thanks and good to know, I will enhance the commit message in V2.

> 
> > of AMD CPPC.
> > 
> > Fixes: 41ea667227ba ("x86, sched: Calculate frequency invariance for AMD systems")
> > Fixes: 3c55e94c0ade ("cpufreq: ACPI: Extend frequency tables to cover boost frequencies")
> > 
> > Reported-by: Jason Bagavatsingham <jason.bagavatsingham@xxxxxxxxx>
> > Tested-by: Jason Bagavatsingham <jason.bagavatsingham@xxxxxxxxx>
> > Signed-off-by: Huang Rui <ray.huang@xxxxxxx>
> > Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> > Cc: Nathan Fontenot <nathan.fontenot@xxxxxxx>
> > Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Cc: Borislav Petkov <bp@xxxxxxx>
> > Cc: x86@xxxxxxxxxx
> > ---
> >  arch/x86/kernel/smpboot.c      | 33 ++++++++++++++++++++++++++-
> >  drivers/cpufreq/acpi-cpufreq.c | 41 ++++++++++++++++++++++++++++++++++
> >  2 files changed, 73 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> > index 02813a7f3a7c..705bc5ceb1ea 100644
> > --- a/arch/x86/kernel/smpboot.c
> > +++ b/arch/x86/kernel/smpboot.c
> > @@ -2033,6 +2033,37 @@ static bool intel_set_max_freq_ratio(void)
> >  }
> >  
> >  #ifdef CONFIG_ACPI_CPPC_LIB
> > +static u64 amd_get_highest_perf(void)
> > +{
> 
> 	struct cpuinfo_x86 *c = &boot_cpu_data;
> 
> and then you can use "c" everywhere.
> 
> > +	u64 cppc_max_perf;
> 
> u64 for something which fits in a byte?
> 
> Also,
> 	max_perf = 255;
> 
> and you can remove the else and default branches below.

I aligned with highest_perf type in get_max_boost_ratio() funciton.

Will clean the "else" and "default" branches in V2.

> 
> > +
> > +	switch (boot_cpu_data.x86) {
> > +	case 0x17:
> > +		if ((boot_cpu_data.x86_model >= 0x30 &&
> > +		     boot_cpu_data.x86_model < 0x40) ||
> > +		    (boot_cpu_data.x86_model >= 0x70 &&
> > +		     boot_cpu_data.x86_model < 0x80))
> > +			cppc_max_perf = 166;
> > +		else
> > +			cppc_max_perf = 255;
> > +		break;
> > +	case 0x19:
> > +		if ((boot_cpu_data.x86_model >= 0x20 &&
> > +		     boot_cpu_data.x86_model < 0x30) ||
> > +		    (boot_cpu_data.x86_model >= 0x40 &&
> > +		     boot_cpu_data.x86_model < 0x70))
> > +			cppc_max_perf = 166;
> > +		else
> > +			cppc_max_perf = 255;
> > +		break;
> > +	default:
> > +		cppc_max_perf = 255;
> > +		break;
> > +	}
> > +
> > +	return cppc_max_perf;
> > +}
> 
> Why is this here and not in arch/x86/kernel/cpu/amd.c?

OK, I will modify to abstract this function in amd.c and then call it both
on smpboot and acpi-cpufreq.

> 
> > +
> >  static bool amd_set_max_freq_ratio(void)
> >  {
> >  	struct cppc_perf_caps perf_caps;
> 
> 
> 
> > @@ -2046,8 +2077,8 @@ static bool amd_set_max_freq_ratio(void)
> >  		return false;
> >  	}
> >  
> > -	highest_perf = perf_caps.highest_perf;
> >  	nominal_perf = perf_caps.nominal_perf;
> > +	highest_perf = amd_get_highest_perf();
> >  
> >  	if (!highest_perf || !nominal_perf) {
> >  		pr_debug("Could not retrieve highest or nominal performance\n");
> > diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> > index d1bbc16fba4b..e5c03360db20 100644
> > --- a/drivers/cpufreq/acpi-cpufreq.c
> > +++ b/drivers/cpufreq/acpi-cpufreq.c
> > @@ -630,6 +630,44 @@ static int acpi_cpufreq_blacklist(struct cpuinfo_x86 *c)
> >  #endif
> >  
> >  #ifdef CONFIG_ACPI_CPPC_LIB
> > +
> > +static u64 get_amd_max_boost_ratio(unsigned int cpu, u64 nominal_perf)
> > +{
> > +	u64 boost_ratio, cppc_max_perf;
> > +
> > +	if (!nominal_perf)
> > +		return 0;
> > +
> > +	switch (boot_cpu_data.x86) {
> > +	case 0x17:
> > +		if ((boot_cpu_data.x86_model >= 0x30 &&
> > +		     boot_cpu_data.x86_model < 0x40) ||
> > +		    (boot_cpu_data.x86_model >= 0x70 &&
> > +		     boot_cpu_data.x86_model < 0x80))
> > +			cppc_max_perf = 166;
> > +		else
> > +			cppc_max_perf = 255;
> > +		break;
> > +	case 0x19:
> > +		if ((boot_cpu_data.x86_model >= 0x20 &&
> > +		     boot_cpu_data.x86_model < 0x30) ||
> > +		    (boot_cpu_data.x86_model >= 0x40 &&
> > +		     boot_cpu_data.x86_model < 0x70))
> > +			cppc_max_perf = 166;
> > +		else
> > +			cppc_max_perf = 255;
> > +		break;
> > +	default:
> > +		cppc_max_perf = 255;
> > +		break;
> 
> This chunk is repeated here. Why?
> 

Yes, I should abstract the funciton in amd.c and avoid the repeated
implementation.

Thanks,
Ray