On Thu, Dec 17, 2020 at 11:44 AM Srinivas Pandruvada <[email protected]> wrote: > > This change tries to address an issue, when BIOS disabled turbo > but HWP_CAP guaranteed is changed later and user space wants to take > advantage of this increased guaranteed performance. > > The HWP_CAP.GUARANTEED value is not a static value. It can be changed > by some out of band agent or during Intel Speed Select performance > level change. The HWP_CAP.MAX still shows max possible performance when > BIOS disabled turbo. So guaranteed can still change as long as this is > same or below HWP_CAP.MAX. > > When guaranteed is changed, the sysfs base_frequency attributes shows > the latest guaranteed frequency. This attribute can be used by user > space software to update scaling min/max frequency. > > Currently the setpolicy callback already uses the latest HWP_CAP > values when setting HWP_REQ. But the verify callback will still restrict > the user settings to the to old guaranteed value. So if the guaranteed > is increased, user space can't take advantage of it. > > To solve this similar to setpolicy callback, read the latest HWP_CAP > values and use it to restrict the maximum setting. This is done by > calling intel_pstate_get_hwp_max(), which already accounts for user > and BIOS turbo disable to get the current max performance. > > This issue is side effect of fixing the issue of scaling frequency > limits by the > 'commit eacc9c5a927e ("cpufreq: intel_pstate: > Fix intel_pstate_get_hwp_max() for turbo disabled")' > The fix resulted in correct setting of reduced scaling frequencies, > but this resulted in capping HWP.REQ to HWP_CAP.GUARANTEED in this case. > > Cc: 5.8+ <[email protected]> # 5.8+ > Signed-off-by: Srinivas Pandruvada <[email protected]> > --- > drivers/cpufreq/intel_pstate.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index 2a4db856222f..7081d1edb22b 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -2199,6 +2199,12 @@ static void > intel_pstate_clear_update_util_hook(unsigned int cpu) > > static int intel_pstate_get_max_freq(struct cpudata *cpu) > { > + if (hwp_active) { > + int turbo_max, max_state; > + > + intel_pstate_get_hwp_max(cpu->cpu, &turbo_max, &max_state);
This would cause intel_pstate_get_hwp_max() to be called twice in intel_pstate_update_perf_limits() which is not perfect. > + return max_state * cpu->pstate.scaling; > + } > return global.turbo_disabled || global.no_turbo ? > cpu->pstate.max_freq : cpu->pstate.turbo_freq; > } > --
