Re: [PATCH 1/2] drm/i915/gt: Allow clobbering gpu resets if the display is off

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

On Mon, Sep 09, 2019 at 11:55:35PM +0100, Chris Wilson wrote:
> If the display is inactive, we need not worry about the gpu reset
> clobbering the display!
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/gt/intel_reset.c | 18 +++++++++++++++++-
>  1 file changed, 17 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> index b9d84d52e986..fe57296b790c 100644
> --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> @@ -7,6 +7,7 @@
>  #include <linux/sched/mm.h>
>  #include <linux/stop_machine.h>
>  
> +#include "display/intel_display.h"
>  #include "display/intel_display_types.h"
>  #include "display/intel_overlay.h"
>  
> @@ -729,6 +730,21 @@ static void nop_submit_request(struct i915_request *request)
>  	intel_engine_queue_breadcrumbs(engine);
>  }
>  
> +static bool reset_clobbers_display(struct drm_i915_private *i915)
> +{
> +	struct intel_crtc *crtc;
> +
> +	if (!INTEL_INFO(i915)->gpu_reset_clobbers_display)
> +		return false;
> +
> +	for_each_intel_crtc(&i915->drm, crtc) {
> +		if (crtc->active)
> +			return true;
> +	}

This feels racy. crtc->active gets set somewhere in the middle of the
modeset, so looks like now we could clobber all the stuff we've already
set up before crtc->active got set.

> +
> +	return false;
> +}
> +
>  static void __intel_gt_set_wedged(struct intel_gt *gt)
>  {
>  	struct intel_engine_cs *engine;
> @@ -755,7 +771,7 @@ static void __intel_gt_set_wedged(struct intel_gt *gt)
>  	awake = reset_prepare(gt);
>  
>  	/* Even if the GPU reset fails, it should still stop the engines */
> -	if (!INTEL_INFO(gt->i915)->gpu_reset_clobbers_display)
> +	if (!reset_clobbers_display(gt->i915))
>  		__intel_gt_reset(gt, ALL_ENGINES);
>  
>  	for_each_engine(engine, gt->i915, id)
> -- 
> 2.23.0
> 
> _______________________________________________
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> Intel-gfx@lists.freedesktop.org
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-- 
Ville Syrjälä
Intel
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