drm/gem: Store client buffer mappings as struct dma_buf_map

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@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201103093015.1063-9-tzimmermann@suse.de

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 @@ err_delete:
 /**
  * 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);
 

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

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);