Re: [PATCH 13/17] drm: push locking down into restore_fbdev_mode

[Daniel Vetter <daniel@ffwll.ch>]

On Sat, May 24, 2014 at 02:30:22PM -0400, Rob Clark wrote:
> All the call-sites save one need locking.  By pushing it down and adding
> a lockless flag, we can use the new spiffy atomic ww_mutex crtc locking
> and simplify all the call-sites.
> 
> Signed-off-by: Rob Clark <robdclark@gmail.com>

Yeah, makes sense. But I don't like the bool lockless interface,
especially since the only user of it is also in the fb helper.

Imo much better to add a static function with __ prefix internal to
drm_fb_helper.c which is lockless and give drivers less rope to hang
themselves. Since I just can't think of a good reason why they want to not
have locking when force-restoring the fbdev emulation.

With that changed this is Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
> ---
>  drivers/gpu/drm/armada/armada_fbdev.c     |  4 +---
>  drivers/gpu/drm/drm_fb_cma_helper.c       |  9 ++-------
>  drivers/gpu/drm/drm_fb_helper.c           | 17 ++++++++---------
>  drivers/gpu/drm/exynos/exynos_drm_fbdev.c |  4 +---
>  drivers/gpu/drm/gma500/psb_drv.c          |  4 +---
>  drivers/gpu/drm/i915/intel_fbdev.c        |  6 +-----
>  drivers/gpu/drm/msm/msm_drv.c             |  7 ++-----
>  drivers/gpu/drm/omapdrm/omap_drv.c        |  4 +---
>  drivers/gpu/drm/tegra/fb.c                |  7 ++-----
>  include/drm/drm_fb_helper.h               |  3 ++-
>  10 files changed, 21 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/gpu/drm/armada/armada_fbdev.c b/drivers/gpu/drm/armada/armada_fbdev.c
> index 948cb14..9976125 100644
> --- a/drivers/gpu/drm/armada/armada_fbdev.c
> +++ b/drivers/gpu/drm/armada/armada_fbdev.c
> @@ -181,10 +181,8 @@ void armada_fbdev_lastclose(struct drm_device *dev)
>  {
>  	struct armada_private *priv = dev->dev_private;
>  
> -	drm_modeset_lock_all(dev);
>  	if (priv->fbdev)
> -		drm_fb_helper_restore_fbdev_mode(priv->fbdev);
> -	drm_modeset_unlock_all(dev);
> +		drm_fb_helper_restore_fbdev_mode(priv->fbdev, false);
>  }
>  
>  void armada_fbdev_fini(struct drm_device *dev)
> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> index 65540b7..ccb7a9ac 100644
> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> @@ -429,13 +429,8 @@ EXPORT_SYMBOL_GPL(drm_fbdev_cma_fini);
>   */
>  void drm_fbdev_cma_restore_mode(struct drm_fbdev_cma *fbdev_cma)
>  {
> -	if (fbdev_cma) {
> -		struct drm_device *dev = fbdev_cma->fb_helper.dev;
> -
> -		drm_modeset_lock_all(dev);
> -		drm_fb_helper_restore_fbdev_mode(&fbdev_cma->fb_helper);
> -		drm_modeset_unlock_all(dev);
> -	}
> +	if (fbdev_cma)
> +		drm_fb_helper_restore_fbdev_mode(&fbdev_cma->fb_helper, false);
>  }
>  EXPORT_SYMBOL_GPL(drm_fbdev_cma_restore_mode);
>  
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 4669e69..3815e1a 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -276,12 +276,15 @@ EXPORT_SYMBOL(drm_fb_helper_debug_leave);
>  /**
>   * drm_fb_helper_restore_fbdev_mode - restore fbdev configuration
>   * @fb_helper: fbcon to restore
> + * @lockless: true in drm_fb_helper_force_kernel_mode() path, to avoid
> + *   blocking in panic case, everywhere else should use false
>   *
>   * This should be called from driver's drm ->lastclose callback
>   * when implementing an fbcon on top of kms using this helper. This ensures that
>   * the user isn't greeted with a black screen when e.g. X dies.
>   */
> -bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper)
> +bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper,
> +		bool lockless)
>  {
>  	struct drm_device *dev = fb_helper->dev;
>  	struct drm_plane *plane;
> @@ -289,9 +292,8 @@ bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper)
>  	struct drm_atomic_state *state;
>  	int i;
>  
> -	drm_warn_on_modeset_not_all_locked(dev);
> -
> -	state = dev->driver->atomic_begin(dev, 0);
> +	state = dev->driver->atomic_begin(dev, lockless ?
> +			DRM_MODE_ATOMIC_NOLOCK : 0);
>  	if (IS_ERR(state)) {
>  		DRM_ERROR("failed to restore fbdev mode\n");
>  		return true;
> @@ -355,7 +357,7 @@ static bool drm_fb_helper_force_kernel_mode(void)
>  			continue;
>  		}
>  
> -		ret = drm_fb_helper_restore_fbdev_mode(helper);
> +		ret = drm_fb_helper_restore_fbdev_mode(helper, true);
>  		if (ret)
>  			error = true;
>  
> @@ -840,7 +842,6 @@ EXPORT_SYMBOL(drm_fb_helper_check_var);
>  int drm_fb_helper_set_par(struct fb_info *info)
>  {
>  	struct drm_fb_helper *fb_helper = info->par;
> -	struct drm_device *dev = fb_helper->dev;
>  	struct fb_var_screeninfo *var = &info->var;
>  
>  	if (var->pixclock != 0) {
> @@ -848,9 +849,7 @@ int drm_fb_helper_set_par(struct fb_info *info)
>  		return -EINVAL;
>  	}
>  
> -	drm_modeset_lock_all(dev);
> -	drm_fb_helper_restore_fbdev_mode(fb_helper);
> -	drm_modeset_unlock_all(dev);
> +	drm_fb_helper_restore_fbdev_mode(fb_helper, false);
>  
>  	if (fb_helper->delayed_hotplug) {
>  		fb_helper->delayed_hotplug = false;
> diff --git a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> index 2371716..486b21f 100644
> --- a/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> +++ b/drivers/gpu/drm/exynos/exynos_drm_fbdev.c
> @@ -375,7 +375,5 @@ void exynos_drm_fbdev_restore_mode(struct drm_device *dev)
>  	if (!private || !private->fb_helper)
>  		return;
>  
> -	drm_modeset_lock_all(dev);
> -	drm_fb_helper_restore_fbdev_mode(private->fb_helper);
> -	drm_modeset_unlock_all(dev);
> +	drm_fb_helper_restore_fbdev_mode(private->fb_helper, false);
>  }
> diff --git a/drivers/gpu/drm/gma500/psb_drv.c b/drivers/gpu/drm/gma500/psb_drv.c
> index 0180292..72a35e3 100644
> --- a/drivers/gpu/drm/gma500/psb_drv.c
> +++ b/drivers/gpu/drm/gma500/psb_drv.c
> @@ -112,11 +112,9 @@ static void psb_driver_lastclose(struct drm_device *dev)
>  	struct drm_psb_private *dev_priv = dev->dev_private;
>  	struct psb_fbdev *fbdev = dev_priv->fbdev;
>  
> -	drm_modeset_lock_all(dev);
> -	ret = drm_fb_helper_restore_fbdev_mode(&fbdev->psb_fb_helper);
> +	ret = drm_fb_helper_restore_fbdev_mode(&fbdev->psb_fb_helper, false);
>  	if (ret)
>  		DRM_DEBUG("failed to restore crtc mode\n");
> -	drm_modeset_unlock_all(dev);
>  
>  	return;
>  }
> diff --git a/drivers/gpu/drm/i915/intel_fbdev.c b/drivers/gpu/drm/i915/intel_fbdev.c
> index fce4a0d..28afd69 100644
> --- a/drivers/gpu/drm/i915/intel_fbdev.c
> +++ b/drivers/gpu/drm/i915/intel_fbdev.c
> @@ -683,11 +683,7 @@ void intel_fbdev_restore_mode(struct drm_device *dev)
>  	if (!dev_priv->fbdev)
>  		return;
>  
> -	drm_modeset_lock_all(dev);
> -
> -	ret = drm_fb_helper_restore_fbdev_mode(&dev_priv->fbdev->helper);
> +	ret = drm_fb_helper_restore_fbdev_mode(&dev_priv->fbdev->helper, false);
>  	if (ret)
>  		DRM_DEBUG("failed to restore crtc mode\n");
> -
> -	drm_modeset_unlock_all(dev);
>  }
> diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
> index 46e0f29..d24ca45 100644
> --- a/drivers/gpu/drm/msm/msm_drv.c
> +++ b/drivers/gpu/drm/msm/msm_drv.c
> @@ -382,11 +382,8 @@ static void msm_preclose(struct drm_device *dev, struct drm_file *file)
>  static void msm_lastclose(struct drm_device *dev)
>  {
>  	struct msm_drm_private *priv = dev->dev_private;
> -	if (priv->fbdev) {
> -		drm_modeset_lock_all(dev);
> -		drm_fb_helper_restore_fbdev_mode(priv->fbdev);
> -		drm_modeset_unlock_all(dev);
> -	}
> +	if (priv->fbdev)
> +		drm_fb_helper_restore_fbdev_mode(priv->fbdev, false);
>  }
>  
>  static irqreturn_t msm_irq(int irq, void *arg)
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c b/drivers/gpu/drm/omapdrm/omap_drv.c
> index 3f64c47..ad082f4 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> @@ -590,9 +590,7 @@ static void dev_lastclose(struct drm_device *dev)
>  		}
>  	}
>  
> -	drm_modeset_lock_all(dev);
> -	ret = drm_fb_helper_restore_fbdev_mode(priv->fbdev);
> -	drm_modeset_unlock_all(dev);
> +	ret = drm_fb_helper_restore_fbdev_mode(priv->fbdev, false);
>  	if (ret)
>  		DBG("failed to restore crtc mode");
>  }
> diff --git a/drivers/gpu/drm/tegra/fb.c b/drivers/gpu/drm/tegra/fb.c
> index f7fca09..85aae37 100644
> --- a/drivers/gpu/drm/tegra/fb.c
> +++ b/drivers/gpu/drm/tegra/fb.c
> @@ -346,11 +346,8 @@ static void tegra_fbdev_free(struct tegra_fbdev *fbdev)
>  
>  void tegra_fbdev_restore_mode(struct tegra_fbdev *fbdev)
>  {
> -	if (fbdev) {
> -		drm_modeset_lock_all(fbdev->base.dev);
> -		drm_fb_helper_restore_fbdev_mode(&fbdev->base);
> -		drm_modeset_unlock_all(fbdev->base.dev);
> -	}
> +	if (fbdev)
> +		drm_fb_helper_restore_fbdev_mode(&fbdev->base, false);
>  }
>  
>  static void tegra_fb_output_poll_changed(struct drm_device *drm)
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 6e622f7..99598a0 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -108,7 +108,8 @@ int drm_fb_helper_set_par(struct fb_info *info);
>  int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
>  			    struct fb_info *info);
>  
> -bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper);
> +bool drm_fb_helper_restore_fbdev_mode(struct drm_fb_helper *fb_helper,
> +		bool lockless);
>  void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helper,
>  			    uint32_t fb_width, uint32_t fb_height);
>  void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
> -- 
> 1.9.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch