Re: [PATCH v3 1/3] powerpc/powernv/idle: Replace CPU features checks with PVR checks

[Pratik Sampat]

On 20/07/20 5:30 am, Nicholas Piggin wrote:
> Excerpts from Pratik Rajesh Sampat's message of July 18, 2020 4:53 am:
> > As the idle framework's architecture is incomplete, hence instead of
> > checking for just the processor type advertised in the device tree CPU
> > features; check for the Processor Version Register (PVR) so that finer
> > granularity can be leveraged while making processor checks.
> >
> > Signed-off-by: Pratik Rajesh Sampat <psampat@xxxxxxxxxxxxx>
> > ---
> >   arch/powerpc/platforms/powernv/idle.c | 14 +++++++-------
> >   1 file changed, 7 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
> > index 2dd467383a88..f62904f70fc6 100644
> > --- a/arch/powerpc/platforms/powernv/idle.c
> > +++ b/arch/powerpc/platforms/powernv/idle.c
> > @@ -92,7 +92,7 @@ static int pnv_save_sprs_for_deep_states(void)
> >   		if (rc != 0)
> >   			return rc;
> >   
> > -		if (cpu_has_feature(CPU_FTR_ARCH_300)) {
> > +		if (pvr_version_is(PVR_POWER9)) {
> >   			rc = opal_slw_set_reg(pir, P9_STOP_SPR_MSR, msr_val);
> >   			if (rc)
> >   				return rc;
> > @@ -116,7 +116,7 @@ static int pnv_save_sprs_for_deep_states(void)
> >   				return rc;
> >   
> >   			/* Only p8 needs to set extra HID regiters */
> > -			if (!cpu_has_feature(CPU_FTR_ARCH_300)) {
> > +			if (!pvr_version_is(PVR_POWER9)) {
> >   
> >   				rc = opal_slw_set_reg(pir, SPRN_HID1, hid1_val);
> >   				if (rc != 0)
> What I think you should do is keep using CPU_FTR_ARCH_300 for this stuff
> which is written for power9 and we know is running on power9, because
> that's a faster test (static branch and does not have to read PVR. And
> then...
>
> > @@ -1205,7 +1205,7 @@ static void __init pnv_probe_idle_states(void)
> >   		return;
> >   	}
> >   
> > -	if (cpu_has_feature(CPU_FTR_ARCH_300))
> > +	if (pvr_version_is(PVR_POWER9))
> >   		pnv_power9_idle_init();
> >   
> >   	for (i = 0; i < nr_pnv_idle_states; i++)
> Here is where you would put the version check. Once we have code that
> can also handle P10 (either by testing CPU_FTR_ARCH_31, or by adding
> an entirely new power10 idle function), then you can add the P10 version
> check here.

Sure, it makes sense to make this check on the top level function and
retain CPU_FTR_ARCH_300 lower in the calls for speed.
I'll make that change.

Thanks
Pratik

> Thanks,
> Nick