[PATCH 02/11] drm/i915/dp_mst: Fix symbol clock when calculating the DSC DPT bpp limit

[Manasi Navare]

On Tue, Mar 26, 2024 at 1:04 PM Manasi Navare <navaremanasi at chromium.org> wrote:
>
> On Tue, Mar 26, 2024 at 3:01 AM Nautiyal, Ankit K
> <ankit.k.nautiyal at intel.com> wrote:
> >
> >
> > On 3/21/2024 1:41 AM, Imre Deak wrote:
> > > The expected link symbol clock unit when calculating the DSC DPT bpp
> > > limit is kSymbols/sec, aligning with the dotclock's kPixels/sec unit
> > > based on the crtc clock. As opposed to this port_clock is used - which
> > > has a 10 kbits/sec unit - with the resulting symbol clock in 10
> > > kSymbols/sec units (disregarding the rounding error for the 13.5Gbps
> > > rate). Fix the calculation using the expected 10x factor.
> > >
> > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> >
> > LGTM.
> >
> > Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal at intel.com>
> >
> > > ---
> > >   drivers/gpu/drm/i915/display/intel_dp_mst.c | 3 +--
> > >   1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_dp_mst.c b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > index 53aec023ce92f..b2bcf66071b05 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_dp_mst.c
> > > @@ -58,8 +58,7 @@ static int intel_dp_mst_check_constraints(struct drm_i915_private *i915, int bpp
> > >   {
> > >       if (intel_dp_is_uhbr(crtc_state) && DISPLAY_VER(i915) < 14 && dsc) {
> > >               int output_bpp = bpp;
> > > -             /* DisplayPort 2 128b/132b, bits per lane is always 32 */
> > > -             int symbol_clock = crtc_state->port_clock / 32;
> > > +             int symbol_clock = intel_dp_link_symbol_clock(crtc_state->port_clock);
>
> Is this correct Symbol clock calculation not needed for UHBR support
> on platforms with DISPLAY_VER = 14 (MTL)?
>
> Manasi

Never mind, the patch [PATCH 05/11] drm/i915/dp_mst: Account with the
DSC DPT bpp limit on MTL answers my question here

Manasi

> > >
> > >               if (output_bpp * adjusted_mode->crtc_clock >=
> > >                   symbol_clock * 72) {