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