Re: [PATCH v3 5/7] drm/gem: Store client buffer mappings as struct dma_buf_map

Daniel Vetter
2020-10-02T13:05:52Z

On Tue, Sep 29, 2020 at 05:14:35PM +0200, Thomas Zimmermann wrote:
> Kernel DRM clients now store their framebuffer address in an instance
> of struct dma_buf_map. Depending on the buffer's location, the address
> refers to system or I/O memory.
>
> Callers of drm_client_buffer_vmap() receive a copy of the value in
> the call's supplied arguments. It can be accessed and modified with
> dma_buf_map interfaces.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
> drivers/gpu/drm/drm_client.c | 34 +++++++++++++++++++--------------
> drivers/gpu/drm/drm_fb_helper.c | 23 +++++++++++++---------
> include/drm/drm_client.h | 7 ++++---
> 3 files changed, 38 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_client.c b/drivers/gpu/drm/drm_client.c
> index ac0082bed966..fe573acf1067 100644
> --- a/drivers/gpu/drm/drm_client.c
> +++ b/drivers/gpu/drm/drm_client.c
> @@ -235,7 +235,7 @@ static void drm_client_buffer_delete(struct drm_client_buffer *buffer)
> {
> struct drm_device *dev = buffer->client->dev;
>
> - drm_gem_vunmap(buffer->gem, buffer->vaddr);
> + drm_gem_vunmap(buffer->gem, &buffer->map);
>
> if (buffer->gem)
> drm_gem_object_put(buffer->gem);
> @@ -291,25 +291,31 @@ drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height, u
> /**
> * drm_client_buffer_vmap - Map DRM client buffer into address space
> * @buffer: DRM client buffer
> + * @map_copy: Returns the mapped memory's address
> *
> * This function maps a client buffer into kernel address space. If the
> - * buffer is already mapped, it returns the mapping's address.
> + * buffer is already mapped, it returns the existing mapping's address.
> *
> * Client buffer mappings are not ref'counted. Each call to
> * drm_client_buffer_vmap() should be followed by a call to
> * drm_client_buffer_vunmap(); or the client buffer should be mapped
> * throughout its lifetime.
> *
> + * The returned address is a copy of the internal value. In contrast to
> + * other vmap interfaces, you don't need it for the client's vunmap
> + * function. So you can modify it at will during blit and draw operations.
> + *
> * Returns:
> - * The mapped memory's address
> + * 0 on success, or a negative errno code otherwise.
> */
> -void *drm_client_buffer_vmap(struct drm_client_buffer *buffer)
> +int
> +drm_client_buffer_vmap(struct drm_client_buffer *buffer, struct dma_buf_map *map_copy)
> {
> - struct dma_buf_map map;
> + struct dma_buf_map *map = &buffer->map;
> int ret;
>
> - if (buffer->vaddr)
> - return buffer->vaddr;
> + if (dma_buf_map_is_set(map))
> + goto out;
>
> /*
> * FIXME: The dependency on GEM here isn't required, we could
> @@ -319,13 +325,14 @@ void *drm_client_buffer_vmap(struct drm_client_buffer *buffer)
> * fd_install step out of the driver backend hooks, to make that
> * final step optional for internal users.
> */
> - ret = drm_gem_vmap(buffer->gem, &map);
> + ret = drm_gem_vmap(buffer->gem, map);
> if (ret)
> - return ERR_PTR(ret);
> + return ret;
>
> - buffer->vaddr = map.vaddr;
> +out:
> + *map_copy = *map;
>
> - return map.vaddr;
> + return 0;
> }
> EXPORT_SYMBOL(drm_client_buffer_vmap);
>
> @@ -339,10 +346,9 @@ EXPORT_SYMBOL(drm_client_buffer_vmap);
> */
> void drm_client_buffer_vunmap(struct drm_client_buffer *buffer)
> {
> - struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(buffer->vaddr);
> + struct dma_buf_map *map = &buffer->map;
>
> - drm_gem_vunmap(buffer->gem, &map);
> - buffer->vaddr = NULL;
> + drm_gem_vunmap(buffer->gem, map);
> }
> EXPORT_SYMBOL(drm_client_buffer_vunmap);
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 8697554ccd41..343a292f2c7c 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -394,7 +394,7 @@ static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
> 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->vaddr + offset;
> + void *dst = fb_helper->buffer->map.vaddr + offset;
> size_t len = (clip->x2 - clip->x1) * cpp;
> unsigned int y;
>
> @@ -416,7 +416,8 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
> struct drm_clip_rect *clip = &helper->dirty_clip;
> struct drm_clip_rect clip_copy;
> unsigned long flags;
> - void *vaddr;
> + struct dma_buf_map map;
> + int ret;
>
> spin_lock_irqsave(&helper->dirty_lock, flags);
> clip_copy = *clip;
> @@ -429,8 +430,8 @@ static void drm_fb_helper_dirty_work(struct work_struct *work)
>
> /* Generic fbdev uses a shadow buffer */
> if (helper->buffer) {
> - vaddr = drm_client_buffer_vmap(helper->buffer);
> - if (IS_ERR(vaddr))
> + ret = drm_client_buffer_vmap(helper->buffer, &map);
> + if (ret)
> return;
> drm_fb_helper_dirty_blit_real(helper, &clip_copy);
> }
> @@ -2076,7 +2077,8 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
> struct drm_framebuffer *fb;
> struct fb_info *fbi;
> u32 format;
> - void *vaddr;
> + struct dma_buf_map map;
> + int ret;
>
> drm_dbg_kms(dev, "surface width(%d), height(%d) and bpp(%d)\n",
> sizes->surface_width, sizes->surface_height,
> @@ -2112,11 +2114,14 @@ static int drm_fb_helper_generic_probe(struct drm_fb_helper *fb_helper,
> fb_deferred_io_init(fbi);
> } else {
> /* buffer is mapped for HW framebuffer */
> - vaddr = drm_client_buffer_vmap(fb_helper->buffer);
> - if (IS_ERR(vaddr))
> - return PTR_ERR(vaddr);
> + ret = drm_client_buffer_vmap(fb_helper->buffer, &map);
> + if (ret)
> + return ret;
> + if (map.is_iomem)
> + fbi->screen_base = map.vaddr_iomem;
> + else
> + fbi->screen_buffer = map.vaddr;
>
> - fbi->screen_buffer = vaddr;
> /* Shamelessly leak the physical address to user-space */
> #if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
> if (drm_leak_fbdev_smem && fbi->fix.smem_start == 0)
> diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
> index 7aaea665bfc2..f07f2fb02e75 100644
> --- a/include/drm/drm_client.h
> +++ b/include/drm/drm_client.h
> @@ -3,6 +3,7 @@
> #ifndef _DRM_CLIENT_H_
> #define _DRM_CLIENT_H_
>
> +#include <linux/dma-buf-map.h>
> #include <linux/lockdep.h>
> #include <linux/mutex.h>
> #include <linux/types.h>
> @@ -141,9 +142,9 @@ struct drm_client_buffer {
> struct drm_gem_object *gem;
>
> /**
> - * @vaddr: Virtual address for the buffer
> + * @map: Virtual address for the buffer
> */
> - void *vaddr;
> + struct dma_buf_map map;
>
> /**
> * @fb: DRM framebuffer
> @@ -155,7 +156,7 @@ struct drm_client_buffer *
> drm_client_framebuffer_create(struct drm_client_dev *client, u32 width, u32 height, u32 format);
> void drm_client_framebuffer_delete(struct drm_client_buffer *buffer);
> int drm_client_framebuffer_flush(struct drm_client_buffer *buffer, struct drm_rect *rect);
> -void *drm_client_buffer_vmap(struct drm_client_buffer *buffer);
> +int drm_client_buffer_vmap(struct drm_client_buffer *buffer, struct dma_buf_map *map);
> void drm_client_buffer_vunmap(struct drm_client_buffer *buffer);
>
> int drm_client_modeset_create(struct drm_client_dev *client);

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

> --
> 2.28.0
>

--
Daniel Vetter
Software Engineer, Intel Corporation