drm/vkms: Compute CRC without change input data

This commit decouples pixel manipulation from compute_crc() for avoiding
any pixel change during the CRC calculation. This commits represents a
preparation work for making VKMS able to support the writeback feature.

Change in V5 (Melissa):
- Rebase and drop bitmap for alpha
Change in V4 (Emil):
- Move bitmap_clear operation and comments to get_pixel function

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Reviewed-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200830142000.146706-3-rodrigosiqueiramelo@gmail.com

diff --git a/drivers/gpu/drm/vkms/vkms_composer.c b/drivers/gpu/drm/vkms/vkms_composer.c
index f67d1ba..c5b32fe 100644 (file)
--- a/drivers/gpu/drm/vkms/vkms_composer.c
+++ b/drivers/gpu/drm/vkms/vkms_composer.c
@@ -9,31 +9,41 @@
 
 #include "vkms_drv.h"
 
+static u32 get_pixel_from_buffer(int x, int y, const u8 *buffer,
+                                const struct vkms_composer *composer)
+{
+       u32 pixel;
+       int src_offset = composer->offset + (y * composer->pitch)
+                                     + (x * composer->cpp);
+
+       pixel = *(u32 *)&buffer[src_offset];
+
+       return pixel;
+}
+
 /**
  * compute_crc - Compute CRC value on output frame
  *
- * @vaddr_out: address to final framebuffer
+ * @vaddr: address to final framebuffer
  * @composer: framebuffer's metadata
  *
  * returns CRC value computed using crc32 on the visible portion of
  * the final framebuffer at vaddr_out
  */
-static uint32_t compute_crc(void *vaddr_out, struct vkms_composer *composer)
+static uint32_t compute_crc(const u8 *vaddr,
+                           const struct vkms_composer *composer)
 {
-       int i, j, src_offset;
+       int x, y;
+       u32 crc = 0, pixel = 0;
        int x_src = composer->src.x1 >> 16;
        int y_src = composer->src.y1 >> 16;
        int h_src = drm_rect_height(&composer->src) >> 16;
        int w_src = drm_rect_width(&composer->src) >> 16;
-       u32 crc = 0;
-
-       for (i = y_src; i < y_src + h_src; ++i) {
-               for (j = x_src; j < x_src + w_src; ++j) {
-                       src_offset = composer->offset
-                                    + (i * composer->pitch)
-                                    + (j * composer->cpp);
-                       crc = crc32_le(crc, vaddr_out + src_offset,
-                                      sizeof(u32));
+
+       for (y = y_src; y < y_src + h_src; ++y) {
+               for (x = x_src; x < x_src + w_src; ++x) {
+                       pixel = get_pixel_from_buffer(x, y, vaddr, composer);
+                       crc = crc32_le(crc, (void *)&pixel, sizeof(u32));
                }
        }