[Nouveau] [PATCH v5 10/10] drm/fb_helper: Support framebuffers in I/O memory
Thomas Zimmermann
tzimmermann at suse.de
Thu Oct 22 08:37:56 UTC 2020
Hi
On 22.10.20 10:05, Daniel Vetter wrote:
> 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>
>> ---
>> 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)
>> +{
>> + const char __iomem *src = info->screen_base + pos;
>
> Maybe a bit much a bikeshed, but I'd write this in terms of drm objects,
> like the dirty_blit function, using the dma_buf_map (instead of the
> fb_info parameter). And then instead of
> screen_base and screen_buffer suffixes give them _mem and _iomem suffixes.
Screen_buffer can be a shadow buffer. Until the blit worker (see
drm_fb_helper_dirty_work() ) completes, it might be more up to date than
the real buffer that's stored in the client.
The orignal fbdev code supported an fb_sync callback to synchronize with
outstanding screen updates (e.g., HW blit ops), but fb_sync is just
overhead here. Copying from screen_buffer or screen_base always returns
the most up-to-date image.
>
> Same for write below. Or I'm not quite understanding why we do it like
> this here - I don't think this code will be used outside of the generic
> fbdev code, so we can always assume that drm_fb_helper->buffer is set up.
It's similar as in the read case. If we write to the client's buffer, an
outstanding blit worker could write the now-outdated shadow buffer over
the user's newly written framebuffer data.
Thinking about it, we might want to schedule the blit worker at the end
of each fb_write, so that the data makes it into the HW buffer in time.
>
> The other thing I think we need is some minimal testcases to make sure.
> The fbtest tool used way back seems to have disappeared, I couldn't find
> a copy of the source anywhere anymore.
As discussed on IRC, I'll add some testcase to the igt test. I'll share
the link here when done.
Best regards
Thomas
>
> With all that: Acked-by: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> Cheers, Daniel
>
>> + size_t alloc_size = min(count, PAGE_SIZE);
>> + ssize_t ret = 0;
>> + char *tmp;
>> +
>> + tmp = kmalloc(alloc_size, GFP_KERNEL);
>> + if (!tmp)
>> + return -ENOMEM;
>> +
>> + 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)
>> +{
>> + 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)
>> +{
>> + 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)
>> +{
>> + 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
>>
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Felix Imendörffer
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