Re: [Intel-gfx] [PATCH] drm/i915: Unbreak check_digital_port_conflicts()

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Dec 07, 2015 at 11:13:20PM +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrj�l� <ville.syrjala@linux.intel.com>
> 
> Atomic changes broke check_digital_port_conflicts(). It needs to look
> at the global situation instead of just trying to find a conflict
> within the current atomic state.
> 
> This bug made my HSW explode spectacularly after I had split the DDI
> encoders into separate DP and HDMI encoders. With the fix, things
> seem much more solid.
> 
> I hope holding the connection_mutex is enough protection that we can
> actually walk the connectors even if they're not part of the current
> atomic state...

That is sufficient locking.
> 
> Cc: stable@vger.kernel.org

Ugh. Long-term I think what we need is for all drivers (well at least
atomic ones) to fill out the possible_clones stuff correctly in the
encoder. And then check this in the atomic helpers. But that's way too
much for -fixes.

On the patch itself, for -fixes: Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
> Fixes: 5448a00d3f06 ("drm/i915: Don't use staged config in check_digital_port_conflicts()")
> Signed-off-by: Ville Syrj�l� <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 1c6d56c84b9d..c902964ceca0 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -12253,18 +12253,23 @@ static void intel_dump_pipe_config(struct intel_crtc *crtc,
>  
>  static bool check_digital_port_conflicts(struct drm_atomic_state *state)
>  {
> -	struct intel_encoder *encoder;
> +	struct drm_device *dev = state->dev;
>  	struct drm_connector *connector;
> -	struct drm_connector_state *connector_state;
>  	unsigned int used_ports = 0;
> -	int i;
>  
>  	/*
>  	 * Walk the connector list instead of the encoder
>  	 * list to detect the problem on ddi platforms
>  	 * where there's just one encoder per digital port.
>  	 */
> -	for_each_connector_in_state(state, connector, connector_state, i) {
> +	drm_for_each_connector(connector, dev) {
> +		struct drm_connector_state *connector_state;
> +		struct intel_encoder *encoder;
> +
> +		connector_state = drm_atomic_get_existing_connector_state(state, connector);
> +		if (!connector_state)
> +			connector_state = connector->state;
> +
>  		if (!connector_state->best_encoder)
>  			continue;
>  
> -- 
> 2.4.10
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch