On Fri, Nov 15, 2019 at 04:07:18PM -0500, Lyude Paul wrote:
> Since nv50_outp_atomic_check_view() can set crtc_state->mode_changed, we
> probably should be calling it before handling any PBN changes. Just a
> precaution.
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: 232c9eec417a ("drm/nouveau: Use atomic VCPI helpers for MST")
> Cc: Ben Skeggs <bskeggs@redhat.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: David Airlie <airlied@redhat.com>
> Cc: Jerry Zuo <Jerry.Zuo@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Juston Li <juston.li@intel.com>
> Cc: Sean Paul <seanpaul@chromium.org>
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Cc: <stable@vger.kernel.org> # v5.1+
> ---
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 44 ++++++++++++++-----------
>  1 file changed, 24 insertions(+), 20 deletions(-)

Looks reasonable:

Reviewed-by: Thierry Reding <treding@nvidia.com>

> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index 549486f1d937..6327aaf37c08 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -770,32 +770,36 @@ nv50_msto_atomic_check(struct drm_encoder *encoder,
>  	struct nv50_mstm *mstm = mstc->mstm;
>  	struct nv50_head_atom *asyh = nv50_head_atom(crtc_state);
>  	int slots;
> +	int ret;
>  
> -	if (crtc_state->mode_changed || crtc_state->connectors_changed) {
> -		/*
> -		 * When restoring duplicated states, we need to make sure that
> -		 * the bw remains the same and avoid recalculating it, as the
> -		 * connector's bpc may have changed after the state was
> -		 * duplicated
> -		 */
> -		if (!state->duplicated) {
> -			const int bpp = connector->display_info.bpc * 3;
> -			const int clock = crtc_state->adjusted_mode.clock;
> +	ret = nv50_outp_atomic_check_view(encoder, crtc_state, conn_state,
> +					  mstc->native);
> +	if (ret)
> +		return ret;
>  
> -			asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp);
> -		}
> +	if (!crtc_state->mode_changed && !crtc_state->connectors_changed)
> +		return 0;
>  
> -		slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr,
> -						      mstc->port,
> -						      asyh->dp.pbn);
> -		if (slots < 0)
> -			return slots;
> +	/*
> +	 * When restoring duplicated states, we need to make sure that the bw
> +	 * remains the same and avoid recalculating it, as the connector's bpc
> +	 * may have changed after the state was duplicated
> +	 */
> +	if (!state->duplicated) {
> +		const int bpp = connector->display_info.bpc * 3;
> +		const int clock = crtc_state->adjusted_mode.clock;
>  
> -		asyh->dp.tu = slots;
> +		asyh->dp.pbn = drm_dp_calc_pbn_mode(clock, bpp);
>  	}
>  
> -	return nv50_outp_atomic_check_view(encoder, crtc_state, conn_state,
> -					   mstc->native);
> +	slots = drm_dp_atomic_find_vcpi_slots(state, &mstm->mgr, mstc->port,
> +					      asyh->dp.pbn);
> +	if (slots < 0)
> +		return slots;
> +
> +	asyh->dp.tu = slots;
> +
> +	return 0;
>  }
>  
>  static void
> -- 
> 2.21.0
> 
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