[PATCH v5 10/10] drm/fb_helper: Support framebuffers in I/O memory
Sam Ravnborg
sam at ravnborg.org
Sat Oct 24 20:38:38 UTC 2020
Hi Thomas.
On Tue, Oct 20, 2020 at 02:20:46PM +0200, Thomas Zimmermann wrote:
> 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.
>
> 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: Thomas Zimmermann <tzimmermann at suse.de>
> Tested-by: Sam Ravnborg <sam at ravnborg.org>
Reviewed-by: Sam Ravnborg <sam at ravnborg.org>
But see a few comments below on naming for you to consider.
Sam
> ---
> Documentation/gpu/todo.rst | 19 ++-
> drivers/gpu/drm/bochs/bochs_kms.c | 1 -
> drivers/gpu/drm/drm_fb_helper.c | 227 ++++++++++++++++++++++++++++--
> include/drm/drm_mode_config.h | 12 --
> 4 files changed, 230 insertions(+), 29 deletions(-)
>
> diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst
> index 7e6fc3c04add..638b7f704339 100644
> --- a/Documentation/gpu/todo.rst
> +++ b/Documentation/gpu/todo.rst
> @@ -197,13 +197,28 @@ 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 at suse.de>, Daniel Vetter
> +
> +Level: Advanced
> +
> +
> drm_framebuffer_funcs and drm_mode_config_funcs.fb_create cleanup
> -----------------------------------------------------------------
>
> diff --git a/drivers/gpu/drm/bochs/bochs_kms.c b/drivers/gpu/drm/bochs/bochs_kms.c
> index 13d0d04c4457..853081d186d5 100644
> --- a/drivers/gpu/drm/bochs/bochs_kms.c
> +++ b/drivers/gpu/drm/bochs/bochs_kms.c
> @@ -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;
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 6212cd7cde1d..1d3180841778 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -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 +2026,206 @@ 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)
The naming here confused me - a name like:
fb_read_iomem() would have helped me more.
With the current naming I shall remember that the screen_base member is
the iomem pointer.
> +{
> + const char __iomem *src = info->screen_base + pos;
> + size_t alloc_size = min(count, PAGE_SIZE);
> + ssize_t ret = 0;
> + char *tmp;
> +
> + tmp = kmalloc(alloc_size, GFP_KERNEL);
> + if (!tmp)
> + return -ENOMEM;
> +
I looked around and could not find other places where
we copy from iomem to mem to usermem in chunks of PAGE_SIZE.
> + while (count) {
> + size_t c = min(count, alloc_size);
> +
> + memcpy_fromio(tmp, src, c);
> + if (copy_to_user(buf, tmp, c)) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + src += c;
> + buf += c;
> + ret += c;
> + count -= c;
> + }
> +
> + kfree(tmp);
> +
> + return ret;
> +}
> +
> +static ssize_t fb_read_screen_buffer(struct fb_info *info, char __user *buf, size_t count,
> + loff_t pos)
And fb_read_sysmem() here.
> +{
> + 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->state != FBINFO_STATE_RUNNING)
> + return -EPERM;
> +
> + 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)
fb_write_iomem()
> +{
> + char __iomem *dst = info->screen_base + pos;
> + size_t alloc_size = min(count, PAGE_SIZE);
> + ssize_t ret = 0;
> + u8 *tmp;
> +
> + tmp = kmalloc(alloc_size, GFP_KERNEL);
> + if (!tmp)
> + return -ENOMEM;
> +
> + while (count) {
> + size_t c = min(count, alloc_size);
> +
> + if (copy_from_user(tmp, buf, c)) {
> + ret = -EFAULT;
> + break;
> + }
> + memcpy_toio(dst, tmp, c);
> +
> + dst += c;
> + buf += c;
> + ret += c;
> + count -= c;
> + }
> +
> + kfree(tmp);
> +
> + return ret;
> +}
> +
> +static ssize_t fb_write_screen_buffer(struct fb_info *info, const char __user *buf, size_t count,
> + loff_t pos)
fb_write_sysmem()
> +{
> + 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;
> +
> + if (info->state != FBINFO_STATE_RUNNING)
> + return -EPERM;
> +
> + 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;
> +
> + if (err)
> + return err;
> +
> + return ret;
> +}
> +
> +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 +2233,11 @@ 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 = {
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 5ffbb4ed5b35..ab424ddd7665 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -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:
> *
> --
> 2.28.0
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