Re: [PATCH] drm/i915: Add a way to test the modeset done during gpu reset.

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

On Tue, Apr 05, 2016 at 12:56:37PM +0200, Maarten Lankhorst wrote:
> Add force_reset_modeset_test as a parameter to force the modeset path during gpu reset.
> This allows a IGT test to set the knob and trigger a hang to force the gpu reset.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Fixes: e2c8b8701e2d ("drm/i915: Use atomic helpers for suspend, v2.")
> Cc: drm-intel-fixes@lists.freedesktop.org

Seems like this should be two patches; One to fix the locking and
another to add the debug knob.

> ---
>  drivers/gpu/drm/i915/i915_params.c   |   6 ++
>  drivers/gpu/drm/i915/i915_params.h   |   1 +
>  drivers/gpu/drm/i915/intel_display.c | 161 ++++++++++++++++++++++++-----------
>  3 files changed, 116 insertions(+), 52 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
> index 1779f02e6df8..80ce581793dc 100644
> --- a/drivers/gpu/drm/i915/i915_params.c
> +++ b/drivers/gpu/drm/i915/i915_params.c
> @@ -45,6 +45,7 @@ struct i915_params i915 __read_mostly = {
>  	.fastboot = 0,
>  	.prefault_disable = 0,
>  	.load_detect_test = 0,
> +	.force_reset_modeset_test = 0,
>  	.reset = true,
>  	.invert_brightness = 0,
>  	.disable_display = 0,
> @@ -158,6 +159,11 @@ MODULE_PARM_DESC(load_detect_test,
>  	"Force-enable the VGA load detect code for testing (default:false). "
>  	"For developers only.");
>  
> +module_param_named_unsafe(force_reset_modeset_test, i915.force_reset_modeset_test, bool, 0600);
> +MODULE_PARM_DESC(force_reset_modeset_test,
> +	"Force a modeset during gpu reset for testing (default:false). "
> +	"For developers only.");
> +
>  module_param_named_unsafe(invert_brightness, i915.invert_brightness, int, 0600);
>  MODULE_PARM_DESC(invert_brightness,
>  	"Invert backlight brightness "
> diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> index 02bc27804291..3934c4300427 100644
> --- a/drivers/gpu/drm/i915/i915_params.h
> +++ b/drivers/gpu/drm/i915/i915_params.h
> @@ -55,6 +55,7 @@ struct i915_params {
>  	bool fastboot;
>  	bool prefault_disable;
>  	bool load_detect_test;
> +	bool force_reset_modeset_test;
>  	bool reset;
>  	bool disable_display;
>  	bool enable_guc_submission;
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index af74cdba7081..acca08797123 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -3119,27 +3119,94 @@ static void intel_update_primary_planes(struct drm_device *dev)
>  	}
>  }
>  
> +static int
> +__intel_display_resume(struct drm_device *dev,
> +		       struct drm_atomic_state *state,
> +		       bool *setup)
> +{
> +	struct drm_crtc_state *crtc_state;
> +	struct drm_crtc *crtc;
> +	int i;
> +
> +	if (!setup || !*setup) {
> +		if (setup)
> +			*setup = true;
> +
> +		intel_modeset_setup_hw_state(dev);
> +		i915_redisable_vga(dev);
> +	}
> +
> +	if (!state)
> +		return 0;
> +
> +	for_each_crtc_in_state(state, crtc, crtc_state, i) {
> +		/*
> +		 * Force recalculation even if we restore
> +		 * current state. With fast modeset this may not result
> +		 * in a modeset when the state is compatible.
> +		 */
> +		crtc_state->mode_changed = true;
> +	}
> +
> +	return drm_atomic_commit(state);
> +}
> +
>  void intel_prepare_reset(struct drm_device *dev)
>  {
> +	bool requires_display_reset = true;
> +	struct drm_atomic_state *state;
> +	struct drm_modeset_acquire_ctx *pctx;
> +	int ret;
> +
>  	/* no reset support for gen2 */
>  	if (IS_GEN2(dev))
>  		return;
>  
>  	/* reset doesn't touch the display */
> -	if (INTEL_INFO(dev)->gen >= 5 || IS_G4X(dev))
> -		return;
> +	if (INTEL_INFO(dev)->gen >= 5 || IS_G4X(dev)) {
> +		if (!i915.force_reset_modeset_test)
> +			return;
> +
> +		requires_display_reset = false;

Can't we just run the full code on g4x+ anyway? Would leave the code
much simpler.

> +	}
>  
>  	drm_modeset_lock_all(dev);
> +	pctx = dev->mode_config.acquire_ctx;

pctx makes me think of power context.

> +
>  	/*
>  	 * Disabling the crtcs gracefully seems nicer. Also the
>  	 * g33 docs say we should at least disable all the planes.
>  	 */
> -	intel_display_suspend(dev);
> +
> +	state = drm_atomic_helper_duplicate_state(dev, pctx);
> +	if (IS_ERR(state)) {
> +		ret = PTR_ERR(state);
> +		state = NULL;
> +		DRM_ERROR("Duplicating state failed with %i\n", ret);
> +		goto err;
> +	}
> +
> +	ret = drm_atomic_helper_disable_all(dev, pctx);
> +	if (ret) {
> +		DRM_ERROR("Suspending crtc's failed with %i\n", ret);
> +		goto err;
> +	}
> +
> +	to_i915(dev)->modeset_restore_state = state;
> +	return;
> +
> +err:
> +	drm_atomic_state_free(state);
> +	if (!requires_display_reset)
> +		drm_modeset_unlock_all(dev);
>  }
>  
>  void intel_finish_reset(struct drm_device *dev)
>  {
>  	struct drm_i915_private *dev_priv = to_i915(dev);
> +	struct drm_atomic_state *state = dev_priv->modeset_restore_state;
> +	bool hpd_init;
> +	int ret;
>  
>  	/*
>  	 * Flips in the rings will be nuked by the reset,
> @@ -3154,36 +3221,48 @@ void intel_finish_reset(struct drm_device *dev)
>  
>  	/* reset doesn't touch the display */
>  	if (INTEL_INFO(dev)->gen >= 5 || IS_G4X(dev)) {
> +		hpd_init = false;
> +
> +		if (!state) {
> +			/*
> +			 * Flips in the rings have been nuked by the reset,
> +			 * so update the base address of all primary
> +			 * planes to the the last fb to make sure we're
> +			 * showing the correct fb after a reset.
> +			 *
> +			 * FIXME: Atomic will make this obsolete since we won't schedule
> +			 * CS-based flips (which might get lost in gpu resets) any more.
> +			 */
> +			intel_update_primary_planes(dev);
> +			return;
> +		}
> +	} else {
>  		/*
> -		 * Flips in the rings have been nuked by the reset,
> -		 * so update the base address of all primary
> -		 * planes to the the last fb to make sure we're
> -		 * showing the correct fb after a reset.
> -		 *
> -		 * FIXME: Atomic will make this obsolete since we won't schedule
> -		 * CS-based flips (which might get lost in gpu resets) any more.
> +		 * The display has been reset as well,
> +		 * so need a full re-initialization.
>  		 */
> -		intel_update_primary_planes(dev);
> -		return;
> -	}
> +		hpd_init = true;
> +		intel_runtime_pm_disable_interrupts(dev_priv);
> +		intel_runtime_pm_enable_interrupts(dev_priv);
>  
> -	/*
> -	 * The display has been reset as well,
> -	 * so need a full re-initialization.
> -	 */
> -	intel_runtime_pm_disable_interrupts(dev_priv);
> -	intel_runtime_pm_enable_interrupts(dev_priv);
> +		intel_modeset_init_hw(dev);
>  
> -	intel_modeset_init_hw(dev);
> +		spin_lock_irq(&dev_priv->irq_lock);
> +		if (dev_priv->display.hpd_irq_setup)
> +			dev_priv->display.hpd_irq_setup(dev);
> +		spin_unlock_irq(&dev_priv->irq_lock);
> +	}
>  
> -	spin_lock_irq(&dev_priv->irq_lock);
> -	if (dev_priv->display.hpd_irq_setup)
> -		dev_priv->display.hpd_irq_setup(dev);
> -	spin_unlock_irq(&dev_priv->irq_lock);
> +	dev_priv->modeset_restore_state = NULL;
> +	if (state)
> +		state->acquire_ctx = dev->mode_config.acquire_ctx;
>  
> -	intel_display_resume(dev);
> +	ret = __intel_display_resume(dev, state, NULL);
> +	if (ret)
> +		DRM_ERROR("Restoring old state failed with %i\n", ret);
>  
> -	intel_hpd_init(dev_priv);
> +	if (hpd_init)
> +		intel_hpd_init(dev_priv);
>  
>  	drm_modeset_unlock_all(dev);
>  }
> @@ -15876,6 +15955,8 @@ void intel_display_resume(struct drm_device *dev)
>  	bool setup = false;
>  
>  	dev_priv->modeset_restore_state = NULL;
> +	if (state)
> +		state->acquire_ctx = &ctx;
>  
>  	/*
>  	 * This is a cludge because with real atomic modeset mode_config.mutex
> @@ -15888,32 +15969,8 @@ void intel_display_resume(struct drm_device *dev)
>  
>  retry:
>  	ret = drm_modeset_lock_all_ctx(dev, &ctx);
> -
> -	if (ret == 0 && !setup) {
> -		setup = true;
> -
> -		intel_modeset_setup_hw_state(dev);
> -		i915_redisable_vga(dev);
> -	}
> -
> -	if (ret == 0 && state) {
> -		struct drm_crtc_state *crtc_state;
> -		struct drm_crtc *crtc;
> -		int i;
> -
> -		state->acquire_ctx = &ctx;
> -
> -		for_each_crtc_in_state(state, crtc, crtc_state, i) {
> -			/*
> -			 * Force recalculation even if we restore
> -			 * current state. With fast modeset this may not result
> -			 * in a modeset when the state is compatible.
> -			 */
> -			crtc_state->mode_changed = true;
> -		}
> -
> -		ret = drm_atomic_commit(state);
> -	}
> +	if (!ret)
> +		ret = __intel_display_resume(dev, state, &setup);
>  
>  	if (ret == -EDEADLK) {
>  		drm_modeset_backoff(&ctx);
> -- 
> 2.1.0
> 
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-- 
Ville Syrjälä
Intel OTC
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