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authorHaixia Shi <hshi@chromium.org>2015-01-30 21:51:14 +0300
committerDave Airlie <airlied@gmail.com>2015-01-31 03:08:47 +0300
commit865844448ce80ccd714793e9ba4140d7ae214229 (patch)
treef98e9afbd1538de669377cde994de9adc2fd75af /drivers/gpu/drm/udl
parente410055331c2f474872b364dce3d4042418e892b (diff)
downloadlinux-865844448ce80ccd714793e9ba4140d7ae214229.tar.xz
drm/udl: optimize udl_compress_hline16 (v2)
The run-length encoding algorithm should compare 16-bit encoded pixel values instead of comparing raw pixel values. It allows pixels with similar but different colors to be encoded as repeat pixels, and thus potentially save USB bandwidth. Signed-off-by: Haixia Shi <hshi@chromium.org> Reviewed-by: Daniel Kurtz <djkurtz@chromium.org> Tested-by: Haixia Shi <hshi@chromium.org> Signed-off-by: Dave Airlie <airlied@gmail.com>
Diffstat (limited to 'drivers/gpu/drm/udl')
-rw-r--r--drivers/gpu/drm/udl/udl_transfer.c39
1 files changed, 19 insertions, 20 deletions
diff --git a/drivers/gpu/drm/udl/udl_transfer.c b/drivers/gpu/drm/udl/udl_transfer.c
index f343db73e095..917dcb978c2c 100644
--- a/drivers/gpu/drm/udl/udl_transfer.c
+++ b/drivers/gpu/drm/udl/udl_transfer.c
@@ -82,12 +82,14 @@ static inline u16 pixel32_to_be16(const uint32_t pixel)
((pixel >> 8) & 0xf800));
}
-static bool pixel_repeats(const void *pixel, const uint32_t repeat, int bpp)
+static inline u16 get_pixel_val16(const uint8_t *pixel, int bpp)
{
+ u16 pixel_val16 = 0;
if (bpp == 2)
- return *(const uint16_t *)pixel == repeat;
- else
- return *(const uint32_t *)pixel == repeat;
+ pixel_val16 = *(const uint16_t *)pixel;
+ else if (bpp == 4)
+ pixel_val16 = pixel32_to_be16(*(const uint32_t *)pixel);
+ return pixel_val16;
}
/*
@@ -134,6 +136,7 @@ static void udl_compress_hline16(
uint8_t *cmd_pixels_count_byte = NULL;
const u8 *raw_pixel_start = NULL;
const u8 *cmd_pixel_start, *cmd_pixel_end = NULL;
+ uint16_t pixel_val16;
prefetchw((void *) cmd); /* pull in one cache line at least */
@@ -154,33 +157,29 @@ static void udl_compress_hline16(
(int)(cmd_buffer_end - cmd) / 2))) * bpp;
prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);
+ pixel_val16 = get_pixel_val16(pixel, bpp);
while (pixel < cmd_pixel_end) {
const u8 *const start = pixel;
- u32 repeating_pixel;
-
- if (bpp == 2) {
- repeating_pixel = *(uint16_t *)pixel;
- *(uint16_t *)cmd = cpu_to_be16(repeating_pixel);
- } else {
- repeating_pixel = *(uint32_t *)pixel;
- *(uint16_t *)cmd = cpu_to_be16(pixel32_to_be16(repeating_pixel));
- }
+ const uint16_t repeating_pixel_val16 = pixel_val16;
+
+ *(uint16_t *)cmd = cpu_to_be16(pixel_val16);
cmd += 2;
pixel += bpp;
- if (unlikely((pixel < cmd_pixel_end) &&
- (pixel_repeats(pixel, repeating_pixel, bpp)))) {
+ while (pixel < cmd_pixel_end) {
+ pixel_val16 = get_pixel_val16(pixel, bpp);
+ if (pixel_val16 != repeating_pixel_val16)
+ break;
+ pixel += bpp;
+ }
+
+ if (unlikely(pixel > start + bpp)) {
/* go back and fill in raw pixel count */
*raw_pixels_count_byte = (((start -
raw_pixel_start) / bpp) + 1) & 0xFF;
- while ((pixel < cmd_pixel_end) &&
- (pixel_repeats(pixel, repeating_pixel, bpp))) {
- pixel += bpp;
- }
-
/* immediately after raw data is repeat byte */
*cmd++ = (((pixel - start) / bpp) - 1) & 0xFF;