linux-kernel - Re: [PATCH v4 2/5] drm/nouveau: Fix nv50_mstc->best

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Date:   Fri, 5 Oct 2018 09:14:40 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Lyude Paul <lyude@...hat.com>
Cc:     nouveau@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        stable@...r.kernel.org, Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Thierry Reding <treding@...dia.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/5] drm/nouveau: Fix nv50_mstc->best_encoder()

On Thu, Oct 04, 2018 at 08:29:51PM -0400, Lyude Paul wrote:
> As mentioned in the previous commit, we currently prevent new modesets
> on recently-removed MST connectors by returning no encoder from our
> ->best_encoder() callback once the MST port has disappeared. This is
> wrong however, because it prevents legacy modesetting users from being
> able to disable CRTCs on MST connectors after the connector's respective
> topology has disappeared.
> 
> So, fix this by instead by just always returning a valid encoder.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> Cc: stable@...r.kernel.org
> 
> Changes since v2:
> - Remove usage of atomic MST helper for now, since that got replaced
>   with a much simpler solution
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>

> ---
>  drivers/gpu/drm/nouveau/dispnv50/disp.c | 14 ++++----------
>  1 file changed, 4 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/dispnv50/disp.c b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> index 5691dfa1db6f..63a23a80f279 100644
> --- a/drivers/gpu/drm/nouveau/dispnv50/disp.c
> +++ b/drivers/gpu/drm/nouveau/dispnv50/disp.c
> @@ -843,22 +843,16 @@ nv50_mstc_atomic_best_encoder(struct drm_connector *connector,
>  {
>  	struct nv50_head *head = nv50_head(connector_state->crtc);
>  	struct nv50_mstc *mstc = nv50_mstc(connector);
> -	if (mstc->port) {
> -		struct nv50_mstm *mstm = mstc->mstm;
> -		return &mstm->msto[head->base.index]->encoder;
> -	}
> -	return NULL;
> +
> +	return &mstc->mstm->msto[head->base.index]->encoder;
>  }
>  
>  static struct drm_encoder *
>  nv50_mstc_best_encoder(struct drm_connector *connector)
>  {
>  	struct nv50_mstc *mstc = nv50_mstc(connector);
> -	if (mstc->port) {
> -		struct nv50_mstm *mstm = mstc->mstm;
> -		return &mstm->msto[0]->encoder;
> -	}
> -	return NULL;
> +
> +	return &mstc->mstm->msto[0]->encoder;
>  }
>  
>  static enum drm_mode_status
> -- 
> 2.17.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch