linux-kernel - Re: [PATCH v4 5/5] drm/i915: Fix intel_dp_mst_best

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Date:   Fri, 5 Oct 2018 09:28:00 +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,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 5/5] drm/i915: Fix intel_dp_mst_best_encoder()

On Thu, Oct 04, 2018 at 08:29:54PM -0400, Lyude Paul wrote:
> Currently, i915 appears to rely on blocking modesets on
> no-longer-present MSTB ports by simply returning NULL for
> ->best_encoder(), which in turn causes any new atomic commits that don't
> disable the CRTC to fail. This is wrong however, since we still want to
> allow userspace to disable CRTCs on no-longer-present MSTB ports by
> changing the DPMS state to off and this still requires that we retrieve
> an encoder.
> 
> So, fix this by always returning a valid encoder regardless of the state
> of the MST port.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> Cc: stable@...r.kernel.org
> 
> Changes since v1:
> - Remove mst atomic helper, since this got replaced with a much simpler
>   solution
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>

With the obvious rebase onto my bikeshed for patch 3:

Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
> ---
>  drivers/gpu/drm/i915/intel_dp_mst.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
> index a366f32b048a..daade60c5714 100644
> --- a/drivers/gpu/drm/i915/intel_dp_mst.c
> +++ b/drivers/gpu/drm/i915/intel_dp_mst.c
> @@ -407,8 +407,6 @@ static struct drm_encoder *intel_mst_atomic_best_encoder(struct drm_connector *c
>  	struct intel_dp *intel_dp = intel_connector->mst_port;
>  	struct intel_crtc *crtc = to_intel_crtc(state->crtc);
>  
> -	if (intel_connector->mst_port_gone)
> -		return NULL;
>  	return &intel_dp->mst_encoders[crtc->pipe]->base.base;
>  }
>  
> -- 
> 2.17.1
> 

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