[PATCH v3] drm/ast: add dmabuf/prime buffer sharing support

[oushixiong <oushixiong@kylinos.cn>]

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This patch adds ast specific codes for DRM prime feature, this is to
allow for offloading of rending in one direction and outputs in other.

This patch is designed to solve the problem that the AST is not displayed
when the server plug in a discrete graphics card at the same time.
We call the dirty callback function to copy the rendering results of the
discrete graphics card to the ast side by dma-buf.

v1->v2:
  - Fix the comment.
v2->v3:
  - we remove the gem_prime_import_sg_table callback and use the
    gem_prime_import callback, because it just map and access the buffer
    with the CPU. and do not to pin the buffer.

Signed-off-by: oushixiong <oushixiong@kylinos.cn>
Acked-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/ast/ast_drv.c  |  27 +++++++
 drivers/gpu/drm/ast/ast_mode.c | 125 ++++++++++++++++++++++++++++++++-
 2 files changed, 151 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/ast/ast_drv.c b/drivers/gpu/drm/ast/ast_drv.c
index 7465c4f0156a..fd3c4bad2eb4 100644
--- a/drivers/gpu/drm/ast/ast_drv.c
+++ b/drivers/gpu/drm/ast/ast_drv.c
@@ -28,6 +28,7 @@
 
 #include <linux/module.h>
 #include <linux/pci.h>
+#include <linux/dma-buf.h>
 
 #include <drm/drm_aperture.h>
 #include <drm/drm_atomic_helper.h>
@@ -50,6 +51,29 @@ module_param_named(modeset, ast_modeset, int, 0400);
 
 DEFINE_DRM_GEM_FOPS(ast_fops);
 
+static struct drm_gem_object *ast_gem_prime_import(struct drm_device *dev,
+						struct dma_buf *dma_buf)
+{
+	struct drm_gem_vram_object *gbo;
+
+	gbo = drm_gem_vram_of_gem(dma_buf->priv);
+	if (gbo->bo.base.dev == dev) {
+		/*
+		 * Importing dmabuf exported from out own gem increases
+		 * refcount on gem itself instead of f_count of dmabuf.
+		 */
+		drm_gem_object_get(&gbo->bo.base);
+		return &gbo->bo.base;
+	}
+
+	gbo = drm_gem_vram_create(dev, dma_buf->size, 0);
+	if (IS_ERR(gbo))
+		return NULL;
+
+	get_dma_buf(dma_buf);
+	return &gbo->bo.base;
+}
+
 static const struct drm_driver ast_driver = {
 	.driver_features = DRIVER_ATOMIC |
 			   DRIVER_GEM |
@@ -63,6 +87,9 @@ static const struct drm_driver ast_driver = {
 	.minor = DRIVER_MINOR,
 	.patchlevel = DRIVER_PATCHLEVEL,
 
+	.prime_fd_to_handle = drm_gem_prime_fd_to_handle,
+	.gem_prime_import = ast_gem_prime_import,
+
 	DRM_GEM_VRAM_DRIVER
 };
 
diff --git a/drivers/gpu/drm/ast/ast_mode.c b/drivers/gpu/drm/ast/ast_mode.c
index 45b56b39ad47..65a4342c5622 100644
--- a/drivers/gpu/drm/ast/ast_mode.c
+++ b/drivers/gpu/drm/ast/ast_mode.c
@@ -48,6 +48,8 @@
 #include "ast_drv.h"
 #include "ast_tables.h"
 
+MODULE_IMPORT_NS(DMA_BUF);
+
 static inline void ast_load_palette_index(struct ast_private *ast,
 				     u8 index, u8 red, u8 green,
 				     u8 blue)
@@ -1535,8 +1537,129 @@ static const struct drm_mode_config_helper_funcs ast_mode_config_helper_funcs =
 	.atomic_commit_tail = drm_atomic_helper_commit_tail_rpm,
 };
 
+static int ast_handle_damage(struct drm_framebuffer *fb, int x, int y,
+					int width, int height)
+{
+	struct drm_gem_vram_object *dst_bo = NULL;
+	void *dst = NULL;
+	int ret = 0, i;
+	unsigned long offset = 0;
+	bool unmap = false;
+	unsigned int bytesPerPixel;
+	struct iosys_map map;
+	struct iosys_map dmabuf_map;
+
+	bytesPerPixel = fb->format->cpp[0];
+
+	if (!fb->obj[0]->dma_buf)
+		return -EINVAL;
+
+	if (!fb->obj[0]->dma_buf->vmap_ptr.vaddr) {
+		ret = dma_buf_vmap(fb->obj[0]->dma_buf, &dmabuf_map);
+		if (ret)
+			return ret;
+	} else
+		dmabuf_map.vaddr = fb->obj[0]->dma_buf->vmap_ptr.vaddr;
+
+	dst_bo = drm_gem_vram_of_gem(fb->obj[0]);
+
+	ret = drm_gem_vram_pin(dst_bo, 0);
+	if (ret) {
+		DRM_ERROR("ast_bo_pin failed\n");
+		return ret;
+	}
+
+	if (!dst_bo->map.vaddr) {
+		ret = drm_gem_vram_vmap(dst_bo, &map);
+		if (ret) {
+			drm_gem_vram_unpin(dst_bo);
+			DRM_ERROR("failed to vmap fbcon\n");
+			return ret;
+		}
+		unmap = true;
+	}
+	dst = dst_bo->map.vaddr;
+
+	for (i = y; i < y + height; i++) {
+		offset = i * fb->pitches[0] + (x * bytesPerPixel);
+		memcpy_toio(dst + offset, dmabuf_map.vaddr + offset,
+			width * bytesPerPixel);
+	}
+
+	if (unmap)
+		drm_gem_vram_vunmap(dst_bo, &map);
+
+	drm_gem_vram_unpin(dst_bo);
+
+	return 0;
+}
+
+
+static int ast_user_framebuffer_dirty(struct drm_framebuffer *fb,
+				struct drm_file *file,
+				unsigned int flags,
+				unsigned int color,
+				struct drm_clip_rect *clips,
+				unsigned int num_clips)
+{
+	int i, ret = 0;
+
+	drm_modeset_lock_all(fb->dev);
+	if (fb->obj[0]->dma_buf) {
+		ret = dma_buf_begin_cpu_access(fb->obj[0]->dma_buf,
+				DMA_FROM_DEVICE);
+		if (ret)
+			goto unlock;
+	}
+
+	for (i = 0; i < num_clips; i++) {
+		ret = ast_handle_damage(fb, clips[i].x1, clips[i].y1,
+				clips[i].x2 - clips[i].x1, clips[i].y2 - clips[i].y1);
+		if (ret)
+			break;
+	}
+
+	if (fb->obj[0]->dma_buf) {
+		dma_buf_end_cpu_access(fb->obj[0]->dma_buf,
+				DMA_FROM_DEVICE);
+	}
+
+unlock:
+	drm_modeset_unlock_all(fb->dev);
+
+	return ret;
+}
+
+static void ast_user_framebuffer_destroy(struct drm_framebuffer *fb)
+{
+	struct iosys_map dmabuf_map;
+
+	if (fb->obj[0]->dma_buf) {
+		dmabuf_map.is_iomem = fb->obj[0]->dma_buf->vmap_ptr.is_iomem;
+		dmabuf_map.vaddr = fb->obj[0]->dma_buf->vmap_ptr.vaddr;
+		if (dmabuf_map.vaddr)
+			dma_buf_vunmap(fb->obj[0]->dma_buf, &dmabuf_map);
+	}
+
+	drm_gem_fb_destroy(fb);
+}
+
+static const struct drm_framebuffer_funcs ast_gem_fb_funcs_dirtyfb = {
+	.destroy	= ast_user_framebuffer_destroy,
+	.create_handle	= drm_gem_fb_create_handle,
+	.dirty		= ast_user_framebuffer_dirty,
+};
+
+static struct drm_framebuffer *
+ast_gem_fb_create_with_dirty(struct drm_device *dev, struct drm_file *file,
+				const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	return drm_gem_fb_create_with_funcs(dev, file, mode_cmd,
+					&ast_gem_fb_funcs_dirtyfb);
+}
+
 static const struct drm_mode_config_funcs ast_mode_config_funcs = {
-	.fb_create = drm_gem_fb_create,
+	.fb_create = ast_gem_fb_create_with_dirty,
 	.mode_valid = drm_vram_helper_mode_valid,
 	.atomic_check = drm_atomic_helper_check,
 	.atomic_commit = drm_atomic_helper_commit,
-- 
2.17.1


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