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[1/2] fbdev: Fix sys_imageblit() for arbitrary image widths

Message ID 20220313192952.12058-2-tzimmermann@suse.de
State New
Headers show
Series fbdev: Fix image blitting for arbitrary image widths | expand

Commit Message

Thomas Zimmermann March 13, 2022, 7:29 p.m. UTC
Commit 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
broke sys_imageblit() for image width that are not aligned to 8-bit
boundaries. Fix this by handling the trailing pixels on each line
separately. The performance improvements in the original commit do not
regress by this change.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
Cc: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Javier Martinez Canillas <javierm@redhat.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
---
 drivers/video/fbdev/core/sysimgblt.c | 29 ++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

Comments

Geert Uytterhoeven March 14, 2022, 8:56 p.m. UTC | #1
Hi Thomas,

On Sun, Mar 13, 2022 at 8:29 PM Thomas Zimmermann <tzimmermann@suse.de> wrote:
> Commit 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
> broke sys_imageblit() for image width that are not aligned to 8-bit
> boundaries. Fix this by handling the trailing pixels on each line
> separately. The performance improvements in the original commit do not
> regress by this change.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

Thanks for fixing! This was very valuable for hammering the bugs
out of ssd130xdrm and the xrgb888-to-mono conversion...

Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
Javier Martinez Canillas March 17, 2022, 11:20 a.m. UTC | #2
Hello Thomas,

On 3/13/22 20:29, Thomas Zimmermann wrote:
> Commit 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
> broke sys_imageblit() for image width that are not aligned to 8-bit
> boundaries. Fix this by handling the trailing pixels on each line
> separately. The performance improvements in the original commit do not
> regress by this change.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Fixes: 6f29e04938bf ("fbdev: Improve performance of sys_imageblit()")
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: Javier Martinez Canillas <javierm@redhat.com>
> Cc: Sam Ravnborg <sam@ravnborg.org>
> ---

Looks good to me. Also Marek and Geert mentioned that fixes the issue
they were seeing.

Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
diff mbox series

Patch

diff --git a/drivers/video/fbdev/core/sysimgblt.c b/drivers/video/fbdev/core/sysimgblt.c
index 722c327a381b..335e92b813fc 100644
--- a/drivers/video/fbdev/core/sysimgblt.c
+++ b/drivers/video/fbdev/core/sysimgblt.c
@@ -188,7 +188,7 @@  static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
 {
 	u32 fgx = fgcolor, bgx = bgcolor, bpp = p->var.bits_per_pixel;
 	u32 ppw = 32/bpp, spitch = (image->width + 7)/8;
-	u32 bit_mask, eorx;
+	u32 bit_mask, eorx, shift;
 	const char *s = image->data, *src;
 	u32 *dst;
 	const u32 *tab;
@@ -229,17 +229,23 @@  static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
 
 	for (i = image->height; i--; ) {
 		dst = dst1;
+		shift = 8;
 		src = s;
 
+		/*
+		 * Manually unroll the per-line copying loop for better
+		 * performance. This works until we processed the last
+		 * completely filled source byte (inclusive).
+		 */
 		switch (ppw) {
 		case 4: /* 8 bpp */
-			for (j = k; j; j -= 2, ++src) {
+			for (j = k; j >= 2; j -= 2, ++src) {
 				*dst++ = colortab[(*src >> 4) & bit_mask];
 				*dst++ = colortab[(*src >> 0) & bit_mask];
 			}
 			break;
 		case 2: /* 16 bpp */
-			for (j = k; j; j -= 4, ++src) {
+			for (j = k; j >= 4; j -= 4, ++src) {
 				*dst++ = colortab[(*src >> 6) & bit_mask];
 				*dst++ = colortab[(*src >> 4) & bit_mask];
 				*dst++ = colortab[(*src >> 2) & bit_mask];
@@ -247,7 +253,7 @@  static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
 			}
 			break;
 		case 1: /* 32 bpp */
-			for (j = k; j; j -= 8, ++src) {
+			for (j = k; j >= 8; j -= 8, ++src) {
 				*dst++ = colortab[(*src >> 7) & bit_mask];
 				*dst++ = colortab[(*src >> 6) & bit_mask];
 				*dst++ = colortab[(*src >> 5) & bit_mask];
@@ -259,6 +265,21 @@  static void fast_imageblit(const struct fb_image *image, struct fb_info *p,
 			}
 			break;
 		}
+
+		/*
+		 * For image widths that are not a multiple of 8, there
+		 * are trailing pixels left on the current line. Print
+		 * them as well.
+		 */
+		for (; j--; ) {
+			shift -= ppw;
+			*dst++ = colortab[(*src >> shift) & bit_mask];
+			if (!shift) {
+				shift = 8;
+				++src;
+			}
+		}
+
 		dst1 += p->fix.line_length;
 		s += spitch;
 	}