Commit 222ec45f authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

drm/fb_helper: Support framebuffers in I/O memory 



At least sparc64 requires I/O-specific access to framebuffers. This
patch updates the fbdev console accordingly.

For drivers with direct access to the framebuffer memory, the callback
functions in struct fb_ops test for the type of memory and call the rsp
fb_sys_ of fb_cfb_ functions. Read and write operations are implemented
internally by DRM's fbdev helper.

For drivers that employ a shadow buffer, fbdev's blit function retrieves
the framebuffer address as struct dma_buf_map, and uses dma_buf_map
interfaces to access the buffer.

The bochs driver on sparc64 uses a workaround to flag the framebuffer as
I/O memory and avoid a HW exception. With the introduction of struct
dma_buf_map, this is not required any longer. The patch removes the rsp
code from both, bochs and fbdev.

v7:
	* use min_t(size_t,) (kernel test robot)
	* return the number of bytes read/written, if any (fbdev testcase)
v5:
	* implement fb_read/fb_write internally (Daniel, Sam)
v4:
	* move dma_buf_map changes into separate patch (Daniel)
	* TODO list: comment on fbdev updates (Daniel)

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: default avatarSam Ravnborg <sam@ravnborg.org>
Tested-by: default avatarSam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201103093015.1063-11-tzimmermann@suse.de
parent b4e7090c

Documentation/gpu/todo.rst

+17 −2
Original line number Diff line number Diff line
@@ -201,13 +201,28 @@ Convert drivers to use drm_fbdev_generic_setup() 
------------------------------------------------



Most drivers can use drm_fbdev_generic_setup(). Driver have to implement

atomic modesetting and GEM vmap support. Current generic fbdev emulation

expects the framebuffer in system memory (or system-like memory).

atomic modesetting and GEM vmap support. Historically, generic fbdev emulation

expected the framebuffer in system memory or system-like memory. By employing

struct dma_buf_map, drivers with frambuffers in I/O memory can be supported

as well.



Contact: Maintainer of the driver you plan to convert



Level: Intermediate



Reimplement functions in drm_fbdev_fb_ops without fbdev

-------------------------------------------------------



A number of callback functions in drm_fbdev_fb_ops could benefit from

being rewritten without dependencies on the fbdev module. Some of the

helpers could further benefit from using struct dma_buf_map instead of

raw pointers.



Contact: Thomas Zimmermann <tzimmermann@suse.de>, Daniel Vetter



Level: Advanced





drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup

-----------------------------------------------------------------

drivers/gpu/drm/bochs/bochs_kms.c

+0 −1
Original line number Diff line number Diff line
@@ -151,7 +151,6 @@ int bochs_kms_init(struct bochs_device *bochs) 
	bochs->dev->mode_config.preferred_depth = 24;

	bochs->dev->mode_config.prefer_shadow = 0;

	bochs->dev->mode_config.prefer_shadow_fbdev = 1;

	bochs->dev->mode_config.fbdev_use_iomem = true;

	bochs->dev->mode_config.quirk_addfb_prefer_host_byte_order = true;



	bochs->dev->mode_config.funcs = &bochs_mode_funcs;

drivers/gpu/drm/drm_fb_helper.c

+206 −14
Original line number Diff line number Diff line
@@ -372,24 +372,22 @@ static void drm_fb_helper_resume_worker(struct work_struct *work) 
}



static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,

					  struct drm_clip_rect *clip)

					  struct drm_clip_rect *clip,

					  struct dma_buf_map *dst)

{

	struct drm_framebuffer *fb = fb_helper->fb;

	unsigned int cpp = fb->format->cpp[0];

	size_t offset = clip->y1 * fb->pitches[0] + clip->x1 * cpp;

	void *src = fb_helper->fbdev->screen_buffer + offset;

	void *dst = fb_helper->buffer->map.vaddr + offset;

	size_t len = (clip->x2 - clip->x1) * cpp;

	unsigned int y;



	for (y = clip->y1; y < clip->y2; y++) {

		if (!fb_helper->dev->mode_config.fbdev_use_iomem)

			memcpy(dst, src, len);

		else

			memcpy_toio((void __iomem *)dst, src, len);

	dma_buf_map_incr(dst, offset); /* go to first pixel within clip rect */



	for (y = clip->y1; y < clip->y2; y++) {

		dma_buf_map_memcpy_to(dst, src, len);

		dma_buf_map_incr(dst, fb->pitches[0]);

		src += fb->pitches[0];

		dst += fb->pitches[0];

	}

}
@@ -417,8 +415,9 @@ static void drm_fb_helper_dirty_work(struct work_struct *work) 
			ret = drm_client_buffer_vmap(helper->buffer, &map);

			if (ret)

				return;

			drm_fb_helper_dirty_blit_real(helper, &clip_copy);

			drm_fb_helper_dirty_blit_real(helper, &clip_copy, &map);

		}



		if (helper->fb->funcs->dirty)

			helper->fb->funcs->dirty(helper->fb, NULL, 0, 0,

						 &clip_copy, 1);
@@ -2027,6 +2026,199 @@ static int drm_fbdev_fb_mmap(struct fb_info *info, struct vm_area_struct *vma) 
		return -ENODEV;

}



static bool drm_fbdev_use_iomem(struct fb_info *info)

{

	struct drm_fb_helper *fb_helper = info->par;

	struct drm_client_buffer *buffer = fb_helper->buffer;



	return !drm_fbdev_use_shadow_fb(fb_helper) && buffer->map.is_iomem;

}



static ssize_t fb_read_screen_base(struct fb_info *info, char __user *buf, size_t count,

				   loff_t pos)

{

	const char __iomem *src = info->screen_base + pos;

	size_t alloc_size = min(count, PAGE_SIZE);

	ssize_t ret = 0;

	int err = 0;

	char *tmp;



	tmp = kmalloc(alloc_size, GFP_KERNEL);

	if (!tmp)

		return -ENOMEM;



	while (count) {

		size_t c = min_t(size_t, count, alloc_size);



		memcpy_fromio(tmp, src, c);

		if (copy_to_user(buf, tmp, c)) {

			err = -EFAULT;

			break;

		}



		src += c;

		buf += c;

		ret += c;

		count -= c;

	}



	kfree(tmp);



	return ret ? ret : err;

}



static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,

				     loff_t pos)

{

	const char *src = info->screen_buffer + pos;



	if (copy_to_user(buf, src, count))

		return -EFAULT;



	return count;

}



static ssize_t drm_fbdev_fb_read(struct fb_info *info, char __user *buf,

				 size_t count, loff_t *ppos)

{

	loff_t pos = *ppos;

	size_t total_size;

	ssize_t ret;



	if (info->screen_size)

		total_size = info->screen_size;

	else

		total_size = info->fix.smem_len;



	if (pos >= total_size)

		return 0;

	if (count >= total_size)

		count = total_size;

	if (total_size - count < pos)

		count = total_size - pos;



	if (drm_fbdev_use_iomem(info))

		ret = fb_read_screen_base(info, buf, count, pos);

	else

		ret = fb_read_screen_buffer(info, buf, count, pos);



	if (ret > 0)

		*ppos += ret;



	return ret;

}



static ssize_t fb_write_screen_base(struct fb_info *info, const char __user *buf, size_t count,

				    loff_t pos)

{

	char __iomem *dst = info->screen_base + pos;

	size_t alloc_size = min(count, PAGE_SIZE);

	ssize_t ret = 0;

	int err = 0;

	u8 *tmp;



	tmp = kmalloc(alloc_size, GFP_KERNEL);

	if (!tmp)

		return -ENOMEM;



	while (count) {

		size_t c = min_t(size_t, count, alloc_size);



		if (copy_from_user(tmp, buf, c)) {

			err = -EFAULT;

			break;

		}

		memcpy_toio(dst, tmp, c);



		dst += c;

		buf += c;

		ret += c;

		count -= c;

	}



	kfree(tmp);



	return ret ? ret : err;

}



static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,

				      loff_t pos)

{

	char *dst = info->screen_buffer + pos;



	if (copy_from_user(dst, buf, count))

		return -EFAULT;



	return count;

}



static ssize_t drm_fbdev_fb_write(struct fb_info *info, const char __user *buf,

				  size_t count, loff_t *ppos)

{

	loff_t pos = *ppos;

	size_t total_size;

	ssize_t ret;

	int err = 0;



	if (info->screen_size)

		total_size = info->screen_size;

	else

		total_size = info->fix.smem_len;



	if (pos > total_size)

		return -EFBIG;

	if (count > total_size) {

		err = -EFBIG;

		count = total_size;

	}

	if (total_size - count < pos) {

		if (!err)

			err = -ENOSPC;

		count = total_size - pos;

	}



	/*

	 * Copy to framebuffer even if we already logged an error. Emulates

	 * the behavior of the original fbdev implementation.

	 */

	if (drm_fbdev_use_iomem(info))

		ret = fb_write_screen_base(info, buf, count, pos);

	else

		ret = fb_write_screen_buffer(info, buf, count, pos);



	if (ret > 0)

		*ppos += ret;



	return ret ? ret : err;

}



static void drm_fbdev_fb_fillrect(struct fb_info *info,

				  const struct fb_fillrect *rect)

{

	if (drm_fbdev_use_iomem(info))

		drm_fb_helper_cfb_fillrect(info, rect);

	else

		drm_fb_helper_sys_fillrect(info, rect);

}



static void drm_fbdev_fb_copyarea(struct fb_info *info,

				  const struct fb_copyarea *area)

{

	if (drm_fbdev_use_iomem(info))

		drm_fb_helper_cfb_copyarea(info, area);

	else

		drm_fb_helper_sys_copyarea(info, area);

}



static void drm_fbdev_fb_imageblit(struct fb_info *info,

				   const struct fb_image *image)

{

	if (drm_fbdev_use_iomem(info))

		drm_fb_helper_cfb_imageblit(info, image);

	else

		drm_fb_helper_sys_imageblit(info, image);

}



static const struct fb_ops drm_fbdev_fb_ops = {

	.owner		= THIS_MODULE,

	DRM_FB_HELPER_DEFAULT_OPS,
@@ -2034,11 +2226,11 @@ static const struct fb_ops drm_fbdev_fb_ops = { 
	.fb_release	= drm_fbdev_fb_release,

	.fb_destroy	= drm_fbdev_fb_destroy,

	.fb_mmap	= drm_fbdev_fb_mmap,

	.fb_read	= drm_fb_helper_sys_read,

	.fb_write	= drm_fb_helper_sys_write,

	.fb_fillrect	= drm_fb_helper_sys_fillrect,

	.fb_copyarea	= drm_fb_helper_sys_copyarea,

	.fb_imageblit	= drm_fb_helper_sys_imageblit,

	.fb_read	= drm_fbdev_fb_read,

	.fb_write	= drm_fbdev_fb_write,

	.fb_fillrect	= drm_fbdev_fb_fillrect,

	.fb_copyarea	= drm_fbdev_fb_copyarea,

	.fb_imageblit	= drm_fbdev_fb_imageblit,

};



static struct fb_deferred_io drm_fbdev_defio = {

include/drm/drm_mode_config.h

+0 −12
Original line number Diff line number Diff line
@@ -877,18 +877,6 @@ struct drm_mode_config { 
	 */

	bool prefer_shadow_fbdev;



	/**

	 * @fbdev_use_iomem:

	 *

	 * Set to true if framebuffer reside in iomem.

	 * When set to true memcpy_toio() is used when copying the framebuffer in

	 * drm_fb_helper.drm_fb_helper_dirty_blit_real().

	 *

	 * FIXME: This should be replaced with a per-mapping is_iomem

	 * flag (like ttm does), and then used everywhere in fbdev code.

	 */

	bool fbdev_use_iomem;



	/**

	 * @quirk_addfb_prefer_xbgr_30bpp:

	 *

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