[Intel-gfx] [PATCH 10/13] drm/i915: Disable DSB usage specifically for LUTs

[Shankar, Uma]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville Syrjala
> Sent: Wednesday, November 23, 2022 8:57 PM
> To: intel-gfx at lists.freedesktop.org
> Subject: [Intel-gfx] [PATCH 10/13] drm/i915: Disable DSB usage specifically for LUTs
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> The DSB has problem loading the LUTs at the moment. Some of that is due to the
> palette anti collision logic, some due to what seem real hw issues. Disable it the
> whole thing locally in the color management code for now.
> 
> Note that we currently have this weird situation where on
> adl+ we load parts of the LUT with DSB and parts with mmio.
> That is due to the fact that only some parts of the LUT code are using the DSB
> register write functions (ivb_load_lut_ext*()), while the rest is using pure mmio
> (bdw_load_lut_10()). So now we'll go back to pure mmio temporarily, until the DSB
> issues get fixed (at which point we should be going for pure DSB).

Yeah, we need to debug and analyze the failure with DSB. If needed,
we can raise a hardware sighting.

For now, let's keep it disabled:
Reviewed-by: Uma Shankar <uma.shankar at intel.com>

> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_color.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_color.c
> b/drivers/gpu/drm/i915/display/intel_color.c
> index 2715f1b617e1..9978d21f1634 100644
> --- a/drivers/gpu/drm/i915/display/intel_color.c
> +++ b/drivers/gpu/drm/i915/display/intel_color.c
> @@ -1394,6 +1394,9 @@ void intel_color_prepare_commit(struct intel_crtc_state
> *crtc_state)  {
>  	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> 
> +	/* FIXME DSB has issues loading LUTs, disable it for now */
> +	return;
> +
>  	crtc_state->dsb = intel_dsb_prepare(crtc);  }
> 
> --
> 2.37.4