[PATCH v4 06/23] drm/connector: hdmi: Use YUV420 output format as an RGB fallback

[Maxime Ripard]

On Thu, May 15, 2025 at 03:44:18PM +0300, Cristian Ciocaltea wrote:
> Hi Maxime,
> 
> On 5/13/25 4:35 PM, Maxime Ripard wrote:
> > Hi,
> > 
> > On Fri, Apr 25, 2025 at 01:26:57PM +0300, Cristian Ciocaltea wrote:
> >> Try to make use of YUV420 when computing the best output format and
> >> RGB cannot be supported for any of the available color depths.
> >>
> >> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea at collabora.com>
> >> ---
> >>  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 22 +++++++++++++++++-----
> >>  1 file changed, 17 insertions(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> >> index 9e0a468073acbb2477eff1abef1c09d63620afaa..1fba10b92a6baa49150b6ff1e96bf2c2739bf269 100644
> >> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> >> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> >> @@ -648,14 +648,26 @@ hdmi_compute_config(const struct drm_connector *connector,
> >>  				       8, connector->max_bpc);
> >>  	int ret;
> >>  
> >> -	/*
> >> -	 * TODO: Add support for YCbCr420 output for HDMI 2.0 capable
> >> -	 * devices, for modes that only support YCbCr420.
> >> -	 */
> >>  	ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
> >>  				      HDMI_COLORSPACE_RGB);
> >> +	if (!ret)
> >> +		return 0;
> > 
> > Sorry, I missed it on the previous iteration, but this condition
> > inversion compared to the rest of the function is throwing me off :)
> > 
> > I believe something like
> > 
> > If (ret) {
> >    if (connector->ycbcr_420_allowed) {
> >       hdmi_compute_format_bpc(..., HDMI_COLORSPACE_YUV420)
> >    } else {
> >      drm_dbg_kms("Can't use YUV420")
> >    }
> > }
> > 
> > Would be more natural
> 
> Yep, will do.
> 
> Please let me know if I can start preparing v5, as I'm not sure if you
> managed to also check the test-related patches.

I haven't gotten through the whole series yet, sorry. I hope to finish
it by ~ the middle of next week.

Maxime
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