[PATCH RFT v2 1/5] drm: Split framebuffer pixel offset calculation from drm_fb_dma_get_gem_addr()

[Chen-Yu Tsai]

Currently drm_fb_dma_get_gem_addr() calculates the offset into the
framebuffer memory for the framebuffer's unclipped source coordinates,
adds that to the framebuffer's backing storage, and returns the result.

We are about to add a variant that uses the clipped source coordinates,
so there is already some reuse of code. However, calculating the data
offset for a given pixel is not specific to the DMA FB helpers. The
offset is only related to the framebuffer.

Split out the offset calculation into a new framebuffer helper so that
non-DMA users can also reuse the same code.

Suggested-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # dependency for next patch
Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
---
Changes since v1:
- New patch
---
 drivers/gpu/drm/drm_fb_dma_helper.c | 28 ++----------------
 drivers/gpu/drm/drm_framebuffer.c   | 45 +++++++++++++++++++++++++++++
 include/drm/drm_framebuffer.h       |  3 ++
 3 files changed, 51 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_dma_helper.c b/drivers/gpu/drm/drm_fb_dma_helper.c
index fd71969d2fb1..ab0f37d8a5ff 100644
--- a/drivers/gpu/drm/drm_fb_dma_helper.c
+++ b/drivers/gpu/drm/drm_fb_dma_helper.c
@@ -75,36 +75,14 @@ dma_addr_t drm_fb_dma_get_gem_addr(struct drm_framebuffer *fb,
 				   unsigned int plane)
 {
 	struct drm_gem_dma_object *obj;
-	dma_addr_t dma_addr;
-	u8 h_div = 1, v_div = 1;
-	u32 block_w = drm_format_info_block_width(fb->format, plane);
-	u32 block_h = drm_format_info_block_height(fb->format, plane);
-	u32 block_size = fb->format->char_per_block[plane];
-	u32 sample_x;
-	u32 sample_y;
-	u32 block_start_y;
-	u32 num_hblocks;
 
 	obj = drm_fb_dma_get_gem_obj(fb, plane);
 	if (!obj)
 		return 0;
 
-	dma_addr = obj->dma_addr + fb->offsets[plane];
-
-	if (plane > 0) {
-		h_div = fb->format->hsub;
-		v_div = fb->format->vsub;
-	}
-
-	sample_x = (state->src_x >> 16) / h_div;
-	sample_y = (state->src_y >> 16) / v_div;
-	block_start_y = (sample_y / block_h) * block_h;
-	num_hblocks = sample_x / block_w;
-
-	dma_addr += fb->pitches[plane] * block_start_y;
-	dma_addr += block_size * num_hblocks;
-
-	return dma_addr;
+	return obj->dma_addr + drm_framebuffer_get_block_offset(fb, plane,
+								state->src_x >> 16,
+								state->src_y >> 16);
 }
 EXPORT_SYMBOL_GPL(drm_fb_dma_get_gem_addr);
 
diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index d32aceb6ca9b..9e1231162047 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -1208,6 +1208,51 @@ void drm_framebuffer_print_info(struct drm_printer *p, unsigned int indent,
 	}
 }
 
+/**
+ * drm_framebuffer_get_block_offset() - Get offset to start of pixel block for
+ * the given framebuffer and coordinates.
+ * @fb: The framebuffer
+ * @plane: Which plane
+ * @x: x coordinate for pixel
+ * @y: y coordinate for pixel
+ *
+ * This function will usually be called from the PLANE callback functions,
+ * or from one of the helpers that calculates the framebuffer's DMA address.
+ *
+ * Return: offset from start of framebuffer to start of pixel block
+ */
+u32 drm_framebuffer_get_block_offset(struct drm_framebuffer *fb, unsigned int plane,
+				     unsigned int x, unsigned int y)
+{
+	u8 h_div = 1, v_div = 1;
+	u32 block_w = drm_format_info_block_width(fb->format, plane);
+	u32 block_h = drm_format_info_block_height(fb->format, plane);
+	u32 block_size = fb->format->char_per_block[plane];
+	u32 sample_x;
+	u32 sample_y;
+	u32 block_start_y;
+	u32 num_hblocks;
+	u32 offset;
+
+	offset = fb->offsets[plane];
+
+	if (plane > 0) {
+		h_div = fb->format->hsub;
+		v_div = fb->format->vsub;
+	}
+
+	sample_x = x / h_div;
+	sample_y = y / v_div;
+	block_start_y = (sample_y / block_h) * block_h;
+	num_hblocks = sample_x / block_w;
+
+	offset += fb->pitches[plane] * block_start_y;
+	offset += block_size * num_hblocks;
+
+	return offset;
+}
+EXPORT_SYMBOL(drm_framebuffer_get_block_offset);
+
 #ifdef CONFIG_DEBUG_FS
 static int drm_framebuffer_info(struct seq_file *m, void *data)
 {
diff --git a/include/drm/drm_framebuffer.h b/include/drm/drm_framebuffer.h
index 38b24fc8978d..c07aea1cc59f 100644
--- a/include/drm/drm_framebuffer.h
+++ b/include/drm/drm_framebuffer.h
@@ -220,6 +220,9 @@ void drm_framebuffer_remove(struct drm_framebuffer *fb);
 void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
 void drm_framebuffer_unregister_private(struct drm_framebuffer *fb);
 
+u32 drm_framebuffer_get_block_offset(struct drm_framebuffer *fb, unsigned int plane,
+				     unsigned int x, unsigned int y);
+
 /**
  * drm_framebuffer_get - acquire a framebuffer reference
  * @fb: DRM framebuffer
-- 
2.55.0.1032.g73a4cd73de-goog