Re: [PATCH 3/6] drm/fb-cma-helper: Support device unplug

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Aug 28, 2017 at 07:17:45PM +0200, Noralf Trønnes wrote:
> Add drm_fbdev_cma_dev_unplug() and use the drm_fb_helper device unplug
> support. Pin driver module on fb_open().
> 
> Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
> ---
>  drivers/gpu/drm/drm_fb_cma_helper.c | 139 +++++++++++++++++-------------------
>  include/drm/drm_fb_cma_helper.h     |   1 +
>  2 files changed, 68 insertions(+), 72 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> index f2ee883..2b044be 100644
> --- a/drivers/gpu/drm/drm_fb_cma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_cma_helper.c
> @@ -25,8 +25,6 @@
>  #include <drm/drm_fb_cma_helper.h>
>  #include <linux/module.h>
>  
> -#define DEFAULT_FBDEFIO_DELAY_MS 50
> -
>  struct drm_fbdev_cma {
>  	struct drm_fb_helper	fb_helper;
>  	const struct drm_framebuffer_funcs *fb_funcs;
> @@ -238,6 +236,34 @@ int drm_fb_cma_debugfs_show(struct seq_file *m, void *arg)
>  EXPORT_SYMBOL_GPL(drm_fb_cma_debugfs_show);
>  #endif
>  
> +static int drm_fbdev_cma_fb_open(struct fb_info *info, int user)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_device *dev = fb_helper->dev;
> +
> +	/*
> +	 * The fb_ops definition resides in this library, meaning fb_open()
> +	 * will take a ref on the library instead of the driver. Make sure the
> +	 * driver module is pinned. Skip fbcon (user==0) since it can detach
> +	 * itself on unregister_framebuffer().
> +	 */
> +	if (user && !try_module_get(dev->driver->fops->owner))
> +		return -ENODEV;

I thought we've fixed this by redoing the fb_ops as a macro? Maybe tinydrm
isn't fixed yet, but then we need to fix up tinydrm. This here otoh kinda
smells a bit like a hack ...

If we need it, then I'd vote to put it into the fbdev helpers, not the cma
specific parts.

> +
> +	return 0;
> +}
> +
> +static int drm_fbdev_cma_fb_release(struct fb_info *info, int user)
> +{
> +	struct drm_fb_helper *fb_helper = info->par;
> +	struct drm_device *dev = fb_helper->dev;
> +
> +	if (user)
> +		module_put(dev->driver->fops->owner);
> +
> +	return 0;
> +}
> +
>  static int drm_fb_cma_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  {
>  	return dma_mmap_writecombine(info->device, vma, info->screen_base,
> @@ -247,10 +273,13 @@ static int drm_fb_cma_mmap(struct fb_info *info, struct vm_area_struct *vma)
>  static struct fb_ops drm_fbdev_cma_ops = {
>  	.owner		= THIS_MODULE,
>  	DRM_FB_HELPER_DEFAULT_OPS,
> +	.fb_open	= drm_fbdev_cma_fb_open,
> +	.fb_release	= drm_fbdev_cma_fb_release,
>  	.fb_fillrect	= drm_fb_helper_sys_fillrect,
>  	.fb_copyarea	= drm_fb_helper_sys_copyarea,
>  	.fb_imageblit	= drm_fb_helper_sys_imageblit,
>  	.fb_mmap	= drm_fb_cma_mmap,
> +	.fb_destroy	= drm_fb_helper_fb_destroy,
>  };
>  
>  static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
> @@ -262,52 +291,26 @@ static int drm_fbdev_cma_deferred_io_mmap(struct fb_info *info,
>  	return 0;
>  }
>  
> -static int drm_fbdev_cma_defio_init(struct fb_info *fbi,
> +static int drm_fbdev_cma_defio_init(struct drm_fb_helper *helper,
>  				    struct drm_gem_cma_object *cma_obj)
>  {
> -	struct fb_deferred_io *fbdefio;
> -	struct fb_ops *fbops;
> +	struct fb_info *fbi = helper->fbdev;
> +	int ret;
>  
> -	/*
> -	 * Per device structures are needed because:
> -	 * fbops: fb_deferred_io_cleanup() clears fbops.fb_mmap
> -	 * fbdefio: individual delays
> -	 */
> -	fbdefio = kzalloc(sizeof(*fbdefio), GFP_KERNEL);
> -	fbops = kzalloc(sizeof(*fbops), GFP_KERNEL);
> -	if (!fbdefio || !fbops) {
> -		kfree(fbdefio);
> -		kfree(fbops);
> -		return -ENOMEM;
> -	}
> +	ret = drm_fb_helper_defio_init(helper);
> +	if (ret)
> +		return ret;
>  
>  	/* can't be offset from vaddr since dirty() uses cma_obj */
>  	fbi->screen_buffer = cma_obj->vaddr;
>  	/* fb_deferred_io_fault() needs a physical address */
>  	fbi->fix.smem_start = page_to_phys(virt_to_page(fbi->screen_buffer));
>  
> -	*fbops = *fbi->fbops;
> -	fbi->fbops = fbops;
> -
> -	fbdefio->delay = msecs_to_jiffies(DEFAULT_FBDEFIO_DELAY_MS);
> -	fbdefio->deferred_io = drm_fb_helper_deferred_io;
> -	fbi->fbdefio = fbdefio;
> -	fb_deferred_io_init(fbi);
>  	fbi->fbops->fb_mmap = drm_fbdev_cma_deferred_io_mmap;
>  
>  	return 0;
>  }
>  
> -static void drm_fbdev_cma_defio_fini(struct fb_info *fbi)
> -{
> -	if (!fbi->fbdefio)
> -		return;
> -
> -	fb_deferred_io_cleanup(fbi);
> -	kfree(fbi->fbdefio);
> -	kfree(fbi->fbops);
> -}
> -

Above changes look like unrelated cleanup? Should be a separate patch I
think.

>  static int
>  drm_fbdev_cma_create(struct drm_fb_helper *helper,
>  	struct drm_fb_helper_surface_size *sizes)
> @@ -365,7 +368,7 @@ drm_fbdev_cma_create(struct drm_fb_helper *helper,
>  	fbi->fix.smem_len = size;
>  
>  	if (fbdev_cma->fb_funcs->dirty) {
> -		ret = drm_fbdev_cma_defio_init(fbi, obj);
> +		ret = drm_fbdev_cma_defio_init(helper, obj);
>  		if (ret)
>  			goto err_cma_destroy;
>  	}
> @@ -399,7 +402,6 @@ struct drm_fbdev_cma *drm_fbdev_cma_init_with_funcs(struct drm_device *dev,
>  	const struct drm_framebuffer_funcs *funcs)
>  {
>  	struct drm_fbdev_cma *fbdev_cma;
> -	struct drm_fb_helper *helper;
>  	int ret;
>  
>  	fbdev_cma = kzalloc(sizeof(*fbdev_cma), GFP_KERNEL);
> @@ -409,37 +411,15 @@ struct drm_fbdev_cma *drm_fbdev_cma_init_with_funcs(struct drm_device *dev,
>  	}
>  	fbdev_cma->fb_funcs = funcs;
>  
> -	helper = &fbdev_cma->fb_helper;
> -
> -	drm_fb_helper_prepare(dev, helper, &drm_fb_cma_helper_funcs);
> -
> -	ret = drm_fb_helper_init(dev, helper, max_conn_count);
> -	if (ret < 0) {
> -		dev_err(dev->dev, "Failed to initialize drm fb helper.\n");
> -		goto err_free;
> -	}
> -
> -	ret = drm_fb_helper_single_add_all_connectors(helper);
> -	if (ret < 0) {
> -		dev_err(dev->dev, "Failed to add connectors.\n");
> -		goto err_drm_fb_helper_fini;
> -
> -	}
> -
> -	ret = drm_fb_helper_initial_config(helper, preferred_bpp);
> -	if (ret < 0) {
> -		dev_err(dev->dev, "Failed to set initial hw configuration.\n");
> -		goto err_drm_fb_helper_fini;
> +	ret = drm_fb_helper_simple_init(dev, &fbdev_cma->fb_helper,
> +					preferred_bpp, max_conn_count,
> +					&drm_fb_cma_helper_funcs);

Yeah the conversion to simple* should be split out I think. But then I
thought more of this will be unified with the overall fbdev helpers?

> +	if (ret) {
> +		kfree(fbdev_cma);
> +		return ERR_PTR(ret);
>  	}
>  
>  	return fbdev_cma;
> -
> -err_drm_fb_helper_fini:
> -	drm_fb_helper_fini(helper);
> -err_free:
> -	kfree(fbdev_cma);
> -
> -	return ERR_PTR(ret);
>  }
>  EXPORT_SYMBOL_GPL(drm_fbdev_cma_init_with_funcs);
>  
> @@ -468,17 +448,15 @@ EXPORT_SYMBOL_GPL(drm_fbdev_cma_init);
>  /**
>   * drm_fbdev_cma_fini() - Free drm_fbdev_cma struct
>   * @fbdev_cma: The drm_fbdev_cma struct
> + *
> + * This function calls drm_fb_helper_simple_fini() and frees @fbdev_cma.
> + *
> + * Don't use this function together with drm_fbdev_cma_dev_unplug().
>   */
>  void drm_fbdev_cma_fini(struct drm_fbdev_cma *fbdev_cma)
>  {
> -	drm_fb_helper_unregister_fbi(&fbdev_cma->fb_helper);
> -	if (fbdev_cma->fb_helper.fbdev)
> -		drm_fbdev_cma_defio_fini(fbdev_cma->fb_helper.fbdev);
> -
> -	if (fbdev_cma->fb_helper.fb)
> -		drm_framebuffer_remove(fbdev_cma->fb_helper.fb);
> -
> -	drm_fb_helper_fini(&fbdev_cma->fb_helper);
> +	if (fbdev_cma)
> +		drm_fb_helper_simple_fini(&fbdev_cma->fb_helper);
>  	kfree(fbdev_cma);
>  }
>  EXPORT_SYMBOL_GPL(drm_fbdev_cma_fini);
> @@ -542,3 +520,20 @@ void drm_fbdev_cma_set_suspend_unlocked(struct drm_fbdev_cma *fbdev_cma,
>  						   state);
>  }
>  EXPORT_SYMBOL(drm_fbdev_cma_set_suspend_unlocked);
> +
> +/**
> + * drm_fbdev_cma_dev_unplug - wrapper around drm_fb_helper_dev_unplug
> + * @fbdev_cma: The drm_fbdev_cma struct, may be NULL
> + *
> + * This unplugs the fbdev emulation for a hotpluggable DRM device. See
> + * drm_fb_helper_dev_unplug() for details.
> + *
> + * Drivers must call drm_mode_config_cleanup() and free @fbdev_cma in their
> + * &drm_driver->release callback.
> + */
> +void drm_fbdev_cma_dev_unplug(struct drm_fbdev_cma *fbdev_cma)
> +{
> +	if (fbdev_cma)
> +		drm_fb_helper_dev_unplug(&fbdev_cma->fb_helper);
> +}

I thought we're trying to phase out the cma helpers, why do we need a
wrapper for a wrapper?

> +EXPORT_SYMBOL(drm_fbdev_cma_dev_unplug);
> diff --git a/include/drm/drm_fb_cma_helper.h b/include/drm/drm_fb_cma_helper.h
> index a323781..a6aafae 100644
> --- a/include/drm/drm_fb_cma_helper.h
> +++ b/include/drm/drm_fb_cma_helper.h
> @@ -27,6 +27,7 @@ void drm_fbdev_cma_hotplug_event(struct drm_fbdev_cma *fbdev_cma);
>  void drm_fbdev_cma_set_suspend(struct drm_fbdev_cma *fbdev_cma, bool state);
>  void drm_fbdev_cma_set_suspend_unlocked(struct drm_fbdev_cma *fbdev_cma,
>  					bool state);
> +void drm_fbdev_cma_dev_unplug(struct drm_fbdev_cma *fbdev_cma);
>  
>  void drm_fb_cma_destroy(struct drm_framebuffer *fb);
>  int drm_fb_cma_create_handle(struct drm_framebuffer *fb,
> -- 
> 2.7.4
> 

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