[PATCH v2] drm/i915/dsc: Change rc parameters calculation for DSC 1.1

[Kandpal, Suraj]

> -----Original Message-----
> From: Tseng, William <william.tseng at intel.com>
> Sent: Friday, February 21, 2025 12:53 PM
> To: Kandpal, Suraj <suraj.kandpal at intel.com>; intel-gfx at lists.freedesktop.org;
> intel-xe at lists.freedesktop.org
> Cc: Heikkila, Juha-pekka <juha-pekka.heikkila at intel.com>
> Subject: RE: [PATCH v2] drm/i915/dsc: Change rc parameters calculation for
> DSC 1.1
> 
> 
> 
> > -----Original Message-----
> > From: Kandpal, Suraj <suraj.kandpal at intel.com>
> > Sent: Friday, February 21, 2025 11:43 AM
> > To: Tseng, William <william.tseng at intel.com>;
> > intel-gfx at lists.freedesktop.org
> > Cc: Heikkila, Juha-pekka <juha-pekka.heikkila at intel.com>
> > Subject: RE: [PATCH v2] drm/i915/dsc: Change rc parameters calculation
> > for DSC 1.1
> >
> >
> >
> > > -----Original Message-----
> > > From: Tseng, William <william.tseng at intel.com>
> > > Sent: Friday, February 21, 2025 7:27 AM
> > > To: intel-gfx at lists.freedesktop.org
> > > Cc: Tseng, William <william.tseng at intel.com>; Kandpal, Suraj
> > > <suraj.kandpal at intel.com>; Heikkila, Juha-pekka <juha-
> > > pekka.heikkila at intel.com>
> > > Subject: [PATCH v2] drm/i915/dsc: Change rc parameters calculation
> > > for DSC 1.1
> >
> > I think you missed one of my previous comments in which I asked you to
> > send it to the intel-xe mailing list So that the CI can test more thoroughly.
> > Also this patch is causing a regression on DG2 + DSC 1.1 config my
> > guess is it would cause a issue on any Machine 13 and above with DSC
> > 1.1 when input bpp is 24 and compressed bpp is 18
> >
> 
> Sorry for missing the comment about the mailing list intel-xe.
> I will send the revised patch to it next time.
> 
> As to the regression concern, I think it won't happen if DSC 1.1 does not support
> the case of input bpp is 24 and compressed bpp is 18.
> What do you think of it?

DSC 1.1 does support input bpc uptil 12 so it should support input bpp of 24 and compressed bpp of 18
I don't see anywhere in the spec where it says otherwise.

> 
> > >
> > > When calculating dsc parameters, the rc parameters calculated by
> > > calculate_rc_params() is incorrect in the case of DSC 1.1 and
> > > DISPLAY_VER(dev_priv) >= 13. It turns out to be some noise-like
> > > lines are displayed on a MIPI DSI panel supporting DSC 1.1.
> > >
> > > The function calculate_rc_params() is implemented by following the
> > > Table E-2 in DSC 1.2a and creates incorrect rc parameters for DSC 1.1.
> > > As a result, add the additional condition
> > > (vdsc_cfg->dsc_version_minor
> > > >= 2) to get the right function to calculate rc parameters for DSC 1.1.
> > >
> > > v1: initial version.
> > > v2: modify the commit comment and change the condition
> > >     regarding DSC version checking.
> > >
> > > Cc: Suraj Kandpal <suraj.kandpal at intel.com>
> > > Cc: Juha-Pekka Heikkil <juha-pekka.heikkila at intel.com>
> > > Signed-off-by: William Tseng <william.tseng at intel.com>
> >
> > Needs a closes-by tag
> >
> 
> Will add closes-by as the line. Is it correct?
> closes-by : https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/13719

It should be Closes: 
My bad
Also lets refrain from sending new patches/ revisions till we root cause this.

Regards,
Suraj Kandpal

> 
> Regards
> William
> 
> > Regards,
> > Suraj Kandpal
> >
> > > ---
> > >  drivers/gpu/drm/i915/display/intel_vdsc.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/i915/display/intel_vdsc.c
> > > b/drivers/gpu/drm/i915/display/intel_vdsc.c
> > > index b355c479eda3..b0a7a2179844 100644
> > > --- a/drivers/gpu/drm/i915/display/intel_vdsc.c
> > > +++ b/drivers/gpu/drm/i915/display/intel_vdsc.c
> > > @@ -320,7 +320,7 @@ int intel_dsc_compute_params(struct
> > > intel_crtc_state
> > > *pipe_config)
> > >  	 * upto uncompressed bpp-1, hence add calculations for all the rc
> > >  	 * parameters
> > >  	 */
> > > -	if (DISPLAY_VER(dev_priv) >= 13) {
> > > +	if (DISPLAY_VER(dev_priv) >= 13 && vdsc_cfg->dsc_version_minor >=
> > > 2) {
> > >  		calculate_rc_params(vdsc_cfg);
> > >  	} else {
> > >  		if ((compressed_bpp == 8 ||
> > > --
> > > 2.34.1