Re: [Intel-gfx] [PATCH v2] drm/atomic: Add the crtc to affected crtc only if uapi.enable = true

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Oct 04, 2021 at 04:36:29AM -0700, Manasi Navare wrote:
> In case of a modeset where a mode gets split across mutiple CRTCs
> in the driver specific implementation (bigjoiner in i915) we wrongly count
> the affected CRTCs based on the drm_crtc_mask and indicate the stolen CRTC as
> an affected CRTC in atomic_check_only().
> This triggers a warning since affected CRTCs doent match requested CRTC.
> 
> To fix this in such bigjoiner configurations, we should only
> increment affected crtcs if that CRTC is enabled in UAPI not
> if it is just used internally in the driver to split the mode.
> 
> There is no way we can adjust requested_crtc calculation as suggested
> in review comments because the crtc gets stolen only after the atomic_check call.

The uapi crtc_state->enable value does not change due to bigjoiner
stealing the crtc. So I don't understand what you're trying to say
here.

The only internal thing that could alter the set of enabled crtcs
on the uapi level is update_connector_routing(true), but that is
always called before drm_atomic_check_only().

> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Simon Ser <contact@emersion.fr>
> Cc: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
> Cc: Daniel Stone <daniels@collabora.com>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> ---
>  drivers/gpu/drm/drm_atomic.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
> index ff1416cd609a..44e7ebf43a2a 100644
> --- a/drivers/gpu/drm/drm_atomic.c
> +++ b/drivers/gpu/drm/drm_atomic.c
> @@ -1360,8 +1360,10 @@ int drm_atomic_check_only(struct drm_atomic_state *state)
>  		}
>  	}
>  
> -	for_each_new_crtc_in_state(state, crtc, new_crtc_state, i)
> -		affected_crtc |= drm_crtc_mask(crtc);
> +	for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
> +		if (new_crtc_state->enable)
> +			affected_crtc |= drm_crtc_mask(crtc);
> +	}
>  
>  	/*
>  	 * For commits that allow modesets drivers can add other CRTCs to the
> -- 
> 2.19.1

-- 
Ville Syrjälä
Intel