Re: [PATCH] drm/i915: vlv: clamp minimum RPS frequency to what Punit allows

Ville Syrjälä
2015-12-07T14:40:57Z

On Fri, Dec 05, 2014 at 11:23:29PM +0200, Ville Syrjälä wrote:
> On Thu, Dec 04, 2014 at 06:39:35PM +0200, Imre Deak wrote:
> > As described in the code comment, I couldn't set the minimum RPS
> > frequency on my BYT-M B0 to the minimum allowed as reported by Punit.
> > Fix this by clamping the minimum value to the first one that was
> > accepted on my machine. This fixes at least the pm_rpm basic-api and
> > min-max-config subtests.
> >
> > Testcase: igt/pm_rps
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_pm.c | 12 +++++++++++-
> > 1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index 45c786f..7a1112f 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -5039,7 +5039,17 @@ static int valleyview_rps_rpe_freq(struct drm_i915_private *dev_priv)
> >
> > static int valleyview_rps_min_freq(struct drm_i915_private *dev_priv)
> > {
> > - return vlv_punit_read(dev_priv, PUNIT_REG_GPU_LFM) & 0xff;
> > + u32 val;
> > +
> > + val = vlv_punit_read(dev_priv, PUNIT_REG_GPU_LFM) & 0xff;
> > + /*
> > + * According to the BYT Punit GPU turbo HAS 1.1.6.3 the minimum value
> > + * for the minimum frequency in GPLL mode is 0xc1. Contrary to this on
> > + * a BYT-M B0 the above register contains 0xbf. Moreover when setting
> > + * a frequency Punit will not allow values below 0xc0. Clamp it 0xc0
> > + * to make sure it matches what Punit accepts.
> > + */
> > + return max_t(u32, val, 0xc0);
>
> Matches what I see on this ffrd as well. But this too has czclk==266.
> Would be interesting to see what happens with other czclks. Anyone
> have a byt w/ 1333 memory?

I guess we never found a 333 SKU. Since the patch is at least correct
for every VLV machine I've ever seen, I think we can go with it.

Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

>
> > }
> >
> > /* Check that the pctx buffer wasn't move under us. */
> > --
> > 1.8.4
> >
> > _______________________________________________
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> > Intel-gfx@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> --
> Ville Syrjälä
> Intel OTC

--
Ville Syrjälä
Intel OTC