[PATCH v6 08/10] drm/gem: Store client buffer mappings as struct dma_buf_map

[Thomas Zimmermann <tzimmermann@xxxxxxx>]

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.

v6:
        * don't call page_to_phys() on framebuffers in I/O memory;
          warn instead (Daniel)

Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
Tested-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
---
 drivers/gpu/drm/drm_client.c    | 34 +++++++++++++++++++--------------
 drivers/gpu/drm/drm_fb_helper.c | 32 ++++++++++++++++++++-----------
 include/drm/drm_client.h        |  7 ++++---
 3 files changed, 45 insertions(+), 28 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 c2f72bb6afb1..6ce0b9119ef2 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -378,7 +378,7 @@ 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;
 
@@ -400,7 +400,8 @@ 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;
@@ -413,8 +414,8 @@ 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);
                }
@@ -2060,7 +2061,8 @@ 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,
@@ -2096,14 +2098,22 @@ 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 */
+               /*
+                * Shamelessly leak the physical address to user-space. As
+                * page_to_phys() is undefined for I/O memory, warn in this
+                * case.
+                */
 #if IS_ENABLED(CONFIG_DRM_FBDEV_LEAK_PHYS_SMEM)
-               if (drm_leak_fbdev_smem && fbi->fix.smem_start == 0)
+               if (drm_leak_fbdev_smem && fbi->fix.smem_start == 0 &&
+                   !drm_WARN_ON_ONCE(dev, map.is_iomem))
                        fbi->fix.smem_start =
                                page_to_phys(virt_to_page(fbi->screen_buffer));
 #endif
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);
-- 
2.29.0