On Mon, Mar 21, 2022 at 07:01:27PM +0200, Souza, Jose wrote:
> On Mon, 2022-03-21 at 12:49 +0200, Stanislav Lisovskiy wrote:
> > We are currently getting FIFO underruns, in particular
> > when PSR2 is enabled. There seem to be no existing workaround
> > or patches, which can fix that issue(were expecting some recent
> > selective fetch update and DBuf bw/SAGV fixes to help,
> > which unfortunately didn't).
> > Current idea is that it looks like for some reason the
> > DBuf prefill time isn't enough once we exit PSR2, despite its
> > theoretically correct.
> > So bump it up a bit by 15%(minimum experimental amount required
> > to get it working), if PSR2 is enabled.
> > For PSR1 there is no need in this hack, so we limit it only
> > to PSR2 and Alderlake.
> >
> > v2: - Added comment(Jose Souza)
> > - Fixed 15% calculation(Jose Souza)
> >
> > Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/display/intel_cdclk.c | 26 ++++++++++++++++++++++
> > 1 file changed, 26 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_cdclk.c b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > index 8888fda8b701..92d57869983a 100644
> > --- a/drivers/gpu/drm/i915/display/intel_cdclk.c
> > +++ b/drivers/gpu/drm/i915/display/intel_cdclk.c
> > @@ -2325,6 +2325,32 @@ int intel_crtc_compute_min_cdclk(const struct intel_crtc_state *crtc_state)
> > dev_priv->max_cdclk_freq));
> > }
> >
> > +
> > + /*
> > + * HACK. We are getting FIFO underruns, in particular
> > + * when PSR2 is enabled. There seem to be no existing workaround
> > + * or patches as of now.
> > + * Current idea is that it looks like for some reason the
> > + * DBuf prefill time isn't enough once we exit PSR2, despite its
> > + * theoretically correct.
> > + * So bump it up a bit by 15%(minimum experimental amount required
> > + * to get it working), if PSR2 is enabled.
> > + * For PSR1 there is no need in this hack, so we limit it only
> > + * to PSR2 and Alderlake.
> > + */
> > + if (IS_ALDERLAKE_P(dev_priv)) {
>
>
> And please check if we can only apply this when two or more pipes are enabled.
> Otherwise this will impact power numbers in the case that is matters most.
That one I can check. Probably need someone at office to disconnect all the pipes, except eDP to see
if its still reproducible, however I think I've seen it already happening.
Stan
>
> > + struct intel_encoder *encoder;
> > +
> > + for_each_intel_encoder_with_psr(&dev_priv->drm, encoder) {
> > + struct intel_dp *intel_dp = enc_to_intel_dp(encoder);
> > +
> > + if (intel_dp->psr.psr2_enabled) {
> > + min_cdclk = DIV_ROUND_UP(min_cdclk * 115, 100);
> > + break;
> > + }
> > + }
> > + }
> > +
> > if (min_cdclk > dev_priv->max_cdclk_freq) {
> > drm_dbg_kms(&dev_priv->drm,
> > "required cdclk (%d kHz) exceeds max (%d kHz)\n",
>
