On Tue, Jan 22, 2019 at 02:49:13PM +0530, Mahesh Kumar wrote:
> Hi,
>
>
> On Mon, Jan 21, 2019 at 9:01 PM Ville Syrjala
> <ville.syrjala@xxxxxxxxxxxxxxx> wrote:
> >
> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > The code managing the dbuf slices is borked and needs some
> > real work to fix. In the meantime let's just stop using the
> > second slice.
> >
> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_pm.c | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> b/drivers/gpu/drm/i915/intel_pm.c
> > index 8b63afa3a221..1e41c899ffe2 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -3618,7 +3618,8 @@ static u8
> intel_enabled_dbuf_slices_num(struct drm_i915_private *dev_priv)
> > enabled_slices = 1;
> >
> > /* Gen prior to GEN11 have only one DBuf slice */
> > - if (INTEL_GEN(dev_priv) < 11)
> > + /* FIXME dbuf slice code is broken: see intel_get_ddb_size() */
> > + if (1 || INTEL_GEN(dev_priv) < 11)
> > return enabled_slices;
>
> IMHO we may not need this,
It's easier to pretend that we have only a single slice. Not sure for
instance if the lack of the above would lead to state check errors (due
to other problems in the dbuf silce implementation).
> If we return from above we'll never disable
> second slice in case it's enabled by bios.
We'll disable whenever we need to, that is during suspend/driver unload.
We can ignore the rest of the cases I think.
> Anyhow code change in intel_get_ddb_size will take care of enabling
> only one slice.
>
> >
> > if (I915_READ(DBUF_CTL_S2) & DBUF_POWER_STATE)
> > @@ -3827,8 +3828,13 @@ static u16 intel_get_ddb_size(struct
> drm_i915_private *dev_priv,
> >
> > /*
> > * 12GB/s is maximum BW supported by single DBuf slice.
> > + *
> > + * FIXME dbuf slice code is broken:
> > + * - must wait for planes to stop using the slice before
> powering it off
>
> AFAIR we were already doing it and disabling slice only after
> update_crtcs, and skl_update_crtc code is taking care of waiting for
> vblank in case it's required.
>
> > + * - plane straddling both slices is illegal in
> multi-pipe scenarios
>
> This is something new :)
>
> although this change introduce a major limitation with number and size
> of planes we can display, yet
> As code is broken and mentioned conditions need to be taken care of,
> This change should be ok until proper fix.
>
> ~Mahesh
>
> > + * - should validate we stay within the hw bandwidth limits
> > */
> > - if (num_active > 1 || total_data_bw >= GBps(12)) {
> > + if (0 && (num_active > 1 || total_data_bw >= GBps(12))) {
> > ddb->enabled_slices = 2;
> > } else {
> > ddb->enabled_slices = 1;
> > --
> > 2.19.2
> >
> > _______________________________________________
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> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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