Re: [Intel-gfx] [PATCH v1 2/3] drm/i915/dsc: force full modeset whenever DSC is enabled at probe

[Jani Nikula <jani.nikula@intel.com>]

On Thu, 13 Feb 2020, Matt Roper <matthew.d.roper@intel.com> wrote:
> On Thu, Feb 13, 2020 at 11:03:29PM +0200, Jani Nikula wrote:
>> On Thu, 13 Feb 2020, Matt Roper <matthew.d.roper@intel.com> wrote:
>> > On Thu, Feb 13, 2020 at 04:04:11PM +0200, Stanislav Lisovskiy wrote:
>> >> From: Jani Nikula <jani.nikula@intel.com>
>> >> 
>> >> We lack full state readout of DSC config, which may lead to DSC enable
>> >> using a config that's all zeros, failing spectacularly. Force full
>> >> modeset and thus compute config at probe to get a sane state, until we
>> >> implement DSC state readout. Any fastset that did appear to work with
>> >> DSC at probe, worked by coincidence. [1] is an example of a change that
>> >> triggered the issue on TGL DSI DSC.
>> >> 
>> >> [1] http://patchwork.freedesktop.org/patch/msgid/20200212150102.7600-1-ville.syrjala@linux.intel.com
>> >> 
>> >> Cc: Manasi Navare <manasi.d.navare@intel.com>
>> >> Cc: Vandita Kulkarni <vandita.kulkarni@intel.com>
>> >> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
>> >> Cc: stable@vger.kernel.org
>> >> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> >
>> > Should this be
>> >
>> > Fixes: fbacb15ea814 ("drm/i915/dsc: add basic hardware state readout support")
>> >
>> > since that's where we added the basic readout with a FIXME to add more
>> > later?
>> 
>> That added some readout and checks, but the problem existed before them
>> too.
>
> Right, but that's as far back as we can go with a fix, right?  Since
> before that we don't even read out enough to know that compression is
> enabled?

Ah, that's right. Any fixes predating that commit would have to be
different. Perhaps we'll just settle for this. ;)

Thanks,
Jani.



>
>
> Matt
>
>> 
>> BR,
>> Jani.
>> 
>> 
>> 
>> >
>> > I don't know the specifics of DSC and what state we need, but the
>> > approach here seems reasonable.
>> >
>> > Acked-by: Matt Roper <matthew.d.roper@intel.com>
>> >
>> >> ---
>> >>  drivers/gpu/drm/i915/display/intel_display.c | 18 ++++++++++++++++++
>> >>  1 file changed, 18 insertions(+)
>> >> 
>> >> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
>> >> index 61ba1f2256a0..1e3f2cc27db8 100644
>> >> --- a/drivers/gpu/drm/i915/display/intel_display.c
>> >> +++ b/drivers/gpu/drm/i915/display/intel_display.c
>> >> @@ -17828,6 +17828,24 @@ static int intel_initial_commit(struct drm_device *dev)
>> >>  			 * have readout for pipe gamma enable.
>> >>  			 */
>> >>  			crtc_state->uapi.color_mgmt_changed = true;
>> >> +
>> >> +			/*
>> >> +			 * FIXME hack to force full modeset when DSC is being
>> >> +			 * used.
>> >> +			 *
>> >> +			 * As long as we do not have full state readout and
>> >> +			 * config comparison of crtc_state->dsc, we have no way
>> >> +			 * to ensure reliable fastset. Remove once we have
>> >> +			 * readout for DSC.
>> >> +			 */
>> >> +			if (crtc_state->dsc.compression_enable) {
>> >> +				ret = drm_atomic_add_affected_connectors(state,
>> >> +									 &crtc->base);
>> >> +				if (ret)
>> >> +					goto out;
>> >> +				crtc_state->uapi.mode_changed = true;
>> >> +				drm_dbg_kms(dev, "Force full modeset for DSC\n");
>> >> +			}
>> >>  		}
>> >>  	}
>> >>  
>> >> -- 
>> >> 2.24.1.485.gad05a3d8e5
>> >> 
>> >> _______________________________________________
>> >> Intel-gfx mailing list
>> >> Intel-gfx@lists.freedesktop.org
>> >> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>> 
>> -- 
>> Jani Nikula, Intel Open Source Graphics Center

-- 
Jani Nikula, Intel Open Source Graphics Center
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