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Message-ID: <57211204.7080703@tronnes.org>
Date:	Wed, 27 Apr 2016 21:24:52 +0200
From:	Noralf Trønnes <noralf@...nnes.org>
To:	dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
	laurent.pinchart@...asonboard.com, tomi.valkeinen@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/7] drm/fb-helper: Add fb_deferred_io support


Den 27.04.2016 21:20, skrev Daniel Vetter:
> On Wed, Apr 27, 2016 at 08:16:32PM +0200, Noralf Trønnes wrote:
>> This adds deferred io support to drm_fb_helper.
>> The fbdev framebuffer changes are flushed using the callback
>> (struct drm_framebuffer *)->funcs->dirty() by a dedicated worker
>> ensuring that it always runs in process context.
>>
>> Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
>> ---
>>
>> Changes since v2:
>> - FB_DEFERRED_IO is now always selected by DRM_KMS_FB_HELPER, ifdef removed
>> - The drm_clip_rect utility functions are dropped, so open code it
>> - docs: use & to denote structs
>>
>> Changes since v1:
>> - Use a dedicated worker to run the framebuffer flushing like qxl does
>> - Add parameter descriptions to drm_fb_helper_deferred_io
>>
>>   drivers/gpu/drm/Kconfig         |   1 +
>>   drivers/gpu/drm/drm_fb_helper.c | 109 +++++++++++++++++++++++++++++++++++++++-
>>   include/drm/drm_fb_helper.h     |  15 ++++++
>>   3 files changed, 124 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
>> index 9e4f2f1..8e6f34b 100644
>> --- a/drivers/gpu/drm/Kconfig
>> +++ b/drivers/gpu/drm/Kconfig
>> @@ -52,6 +52,7 @@ config DRM_KMS_FB_HELPER
>>   	select FB_CFB_FILLRECT
>>   	select FB_CFB_COPYAREA
>>   	select FB_CFB_IMAGEBLIT
>> +	select FB_DEFERRED_IO
>>   	help
>>   	  FBDEV helpers for KMS drivers.
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
>> index 855108e..5112b5d 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -48,6 +48,8 @@ MODULE_PARM_DESC(fbdev_emulation,
>>
>>   static LIST_HEAD(kernel_fb_helper_list);
>>
>> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper);
> Instead of this forward decl just inline the few setup commands into
> drm_fb_helper_prepare.

That would mean that I have to forward declare drm_fb_helper_dirty_work()
instead. Is that better?
Or should I relocate the functions?

>> +
>>   /**
>>    * DOC: fbdev helpers
>>    *
>> @@ -84,6 +86,15 @@ static LIST_HEAD(kernel_fb_helper_list);
>>    * and set up an initial configuration using the detected hardware, drivers
>>    * should call drm_fb_helper_single_add_all_connectors() followed by
>>    * drm_fb_helper_initial_config().
>> + *
>> + * If CONFIG_FB_DEFERRED_IO is enabled and &drm_framebuffer_funcs ->dirty is
>> + * set, the drm_fb_helper_{cfb,sys}_{write,fillrect,copyarea,imageblit}
>> + * functions will accumulate changes and schedule &fb_helper .dirty_work to run
>> + * right away. This worker then calls the dirty() function ensuring that it
>> + * will always run in process context since the fb_*() function could be
>> + * running in atomic context. If drm_fb_helper_deferred_io() is used as the
>> + * deferred_io callback it will also schedule dirty_work with the damage
>> + * collected from the mmap page writes.
>>    */
>>
>>   /**
>> @@ -650,6 +661,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
>>   			   const struct drm_fb_helper_funcs *funcs)
>>   {
>>   	INIT_LIST_HEAD(&helper->kernel_fb_list);
>> +	drm_fb_helper_dirty_init(helper);
>>   	helper->funcs = funcs;
>>   	helper->dev = dev;
>>   }
>> @@ -834,6 +846,82 @@ void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_unlink_fbi);
>>
>> +static void drm_fb_helper_dirty_work(struct work_struct *work)
>> +{
>> +	struct drm_fb_helper *helper = container_of(work, struct drm_fb_helper,
>> +						    dirty_work);
>> +	struct drm_clip_rect *clip = &helper->dirty_clip;
>> +	struct drm_clip_rect clip_copy;
>> +	unsigned long flags;
>> +
>> +	spin_lock_irqsave(&helper->dirty_lock, flags);
>> +	clip_copy = *clip;
>> +	clip->x1 = clip->y1 = ~0;
>> +	clip->x2 = clip->y2 = 0;
>> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
>> +
>> +	helper->fb->funcs->dirty(helper->fb, NULL, 0, 0, &clip_copy, 1);
>> +}
>> +
>> +static void drm_fb_helper_dirty_init(struct drm_fb_helper *helper)
>> +{
>> +	spin_lock_init(&helper->dirty_lock);
>> +	INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
>> +	helper->dirty_clip.x1 = helper->dirty_clip.y1 = ~0;
>> +}
>> +
>> +static void drm_fb_helper_dirty(struct fb_info *info, u32 x, u32 y,
>> +				u32 width, u32 height)
>> +{
>> +	struct drm_fb_helper *helper = info->par;
>> +	struct drm_clip_rect *clip = &helper->dirty_clip;
>> +	unsigned long flags;
>> +
>> +	if (!helper->fb->funcs->dirty)
>> +		return;
>> +
>> +	spin_lock_irqsave(&helper->dirty_lock, flags);
>> +	clip->x1 = min_t(u32, clip->x1, x);
>> +	clip->y1 = min_t(u32, clip->y1, y);
>> +	clip->x2 = max_t(u32, clip->x2, x + width);
>> +	clip->y2 = max_t(u32, clip->y2, y + height);
>> +	spin_unlock_irqrestore(&helper->dirty_lock, flags);
>> +
>> +	schedule_work(&helper->dirty_work);
>> +}
>> +
>> +/**
>> + * drm_fb_helper_deferred_io() - fbdev deferred_io callback function
>> + * @info: fb_info struct pointer
>> + * @pagelist: list of dirty mmap framebuffer pages
>> + *
>> + * This function is used as the &fb_deferred_io ->deferred_io
>> + * callback function for flushing the fbdev mmap writes.
>> + */
>> +void drm_fb_helper_deferred_io(struct fb_info *info,
>> +			       struct list_head *pagelist)
>> +{
>> +	unsigned long start, end, min, max;
>> +	struct page *page;
>> +	u32 y1, y2;
>> +
>> +	min = ULONG_MAX;
>> +	max = 0;
>> +	list_for_each_entry(page, pagelist, lru) {
>> +		start = page->index << PAGE_SHIFT;
>> +		end = start + PAGE_SIZE - 1;
>> +		min = min(min, start);
>> +		max = max(max, end);
>> +	}
>> +
>> +	if (min < max) {
>> +		y1 = min / info->fix.line_length;
>> +		y2 = min_t(u32, max / info->fix.line_length, info->var.yres);
> Needs a DIV_ROUND_UP here I think.
>
> Besides these two nits nothing else I've spotted.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
>
>
>> +		drm_fb_helper_dirty(info, 0, y1, info->var.xres, y2 - y1);
>> +	}
>> +}
>> +EXPORT_SYMBOL(drm_fb_helper_deferred_io);
>> +
>>   /**
>>    * drm_fb_helper_sys_read - wrapper around fb_sys_read
>>    * @info: fb_info struct pointer
>> @@ -862,7 +950,14 @@ EXPORT_SYMBOL(drm_fb_helper_sys_read);
>>   ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
>>   				size_t count, loff_t *ppos)
>>   {
>> -	return fb_sys_write(info, buf, count, ppos);
>> +	ssize_t ret;
>> +
>> +	ret = fb_sys_write(info, buf, count, ppos);
>> +	if (ret > 0)
>> +		drm_fb_helper_dirty(info, 0, 0, info->var.xres,
>> +				    info->var.yres);
>> +
>> +	return ret;
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_write);
>>
>> @@ -877,6 +972,8 @@ void drm_fb_helper_sys_fillrect(struct fb_info *info,
>>   				const struct fb_fillrect *rect)
>>   {
>>   	sys_fillrect(info, rect);
>> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
>> +			    rect->width, rect->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_fillrect);
>>
>> @@ -891,6 +988,8 @@ void drm_fb_helper_sys_copyarea(struct fb_info *info,
>>   				const struct fb_copyarea *area)
>>   {
>>   	sys_copyarea(info, area);
>> +	drm_fb_helper_dirty(info, area->dx, area->dy,
>> +			    area->width, area->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_copyarea);
>>
>> @@ -905,6 +1004,8 @@ void drm_fb_helper_sys_imageblit(struct fb_info *info,
>>   				 const struct fb_image *image)
>>   {
>>   	sys_imageblit(info, image);
>> +	drm_fb_helper_dirty(info, image->dx, image->dy,
>> +			    image->width, image->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_sys_imageblit);
>>
>> @@ -919,6 +1020,8 @@ void drm_fb_helper_cfb_fillrect(struct fb_info *info,
>>   				const struct fb_fillrect *rect)
>>   {
>>   	cfb_fillrect(info, rect);
>> +	drm_fb_helper_dirty(info, rect->dx, rect->dy,
>> +			    rect->width, rect->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_cfb_fillrect);
>>
>> @@ -933,6 +1036,8 @@ void drm_fb_helper_cfb_copyarea(struct fb_info *info,
>>   				const struct fb_copyarea *area)
>>   {
>>   	cfb_copyarea(info, area);
>> +	drm_fb_helper_dirty(info, area->dx, area->dy,
>> +			    area->width, area->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_cfb_copyarea);
>>
>> @@ -947,6 +1052,8 @@ void drm_fb_helper_cfb_imageblit(struct fb_info *info,
>>   				 const struct fb_image *image)
>>   {
>>   	cfb_imageblit(info, image);
>> +	drm_fb_helper_dirty(info, image->dx, image->dy,
>> +			    image->width, image->height);
>>   }
>>   EXPORT_SYMBOL(drm_fb_helper_cfb_imageblit);
>>
>> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
>> index 062723b..5b4aa35 100644
>> --- a/include/drm/drm_fb_helper.h
>> +++ b/include/drm/drm_fb_helper.h
>> @@ -172,6 +172,10 @@ struct drm_fb_helper_connector {
>>    * @funcs: driver callbacks for fb helper
>>    * @fbdev: emulated fbdev device info struct
>>    * @pseudo_palette: fake palette of 16 colors
>> + * @dirty_clip: clip rectangle used with deferred_io to accumulate damage to
>> + *              the screen buffer
>> + * @dirty_lock: spinlock protecting @dirty_clip
>> + * @dirty_work: worker used to flush the framebuffer
>>    *
>>    * This is the main structure used by the fbdev helpers. Drivers supporting
>>    * fbdev emulation should embedded this into their overall driver structure.
>> @@ -189,6 +193,9 @@ struct drm_fb_helper {
>>   	const struct drm_fb_helper_funcs *funcs;
>>   	struct fb_info *fbdev;
>>   	u32 pseudo_palette[17];
>> +	struct drm_clip_rect dirty_clip;
>> +	spinlock_t dirty_lock;
>> +	struct work_struct dirty_work;
>>
>>   	/**
>>   	 * @kernel_fb_list:
>> @@ -245,6 +252,9 @@ void drm_fb_helper_fill_fix(struct fb_info *info, uint32_t pitch,
>>
>>   void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper);
>>
>> +void drm_fb_helper_deferred_io(struct fb_info *info,
>> +			       struct list_head *pagelist);
>> +
>>   ssize_t drm_fb_helper_sys_read(struct fb_info *info, char __user *buf,
>>   			       size_t count, loff_t *ppos);
>>   ssize_t drm_fb_helper_sys_write(struct fb_info *info, const char __user *buf,
>> @@ -368,6 +378,11 @@ static inline void drm_fb_helper_unlink_fbi(struct drm_fb_helper *fb_helper)
>>   {
>>   }
>>
>> +static inline void drm_fb_helper_deferred_io(struct fb_info *info,
>> +					     struct list_head *pagelist)
>> +{
>> +}
>> +
>>   static inline ssize_t drm_fb_helper_sys_read(struct fb_info *info,
>>   					     char __user *buf, size_t count,
>>   					     loff_t *ppos)
>> --
>> 2.2.2
>>

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