On Sun, Mar 13, 2022 at 08:29:52PM +0100, Thomas Zimmermann wrote:
> Commit 0d03011894d2 ("fbdev: Improve performance of cfb_imageblit()")
> broke cfb_imageblit() for image widths 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@xxxxxxx>
> Fixes: 0d03011894d2 ("fbdev: Improve performance of cfb_imageblit()")
> Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: Javier Martinez Canillas <javierm@xxxxxxxxxx>
> Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> Acked-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
> Reviewed-by: Javier Martinez Canillas <javierm@xxxxxxxxxx>
Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> ---
> drivers/video/fbdev/core/cfbimgblt.c | 28 ++++++++++++++++++++++++----
> 1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/video/fbdev/core/cfbimgblt.c b/drivers/video/fbdev/core/cfbimgblt.c
> index 7361cfabdd85..9ebda4e0dc7a 100644
> --- a/drivers/video/fbdev/core/cfbimgblt.c
> +++ b/drivers/video/fbdev/core/cfbimgblt.c
> @@ -218,7 +218,7 @@ static inline void fast_imageblit(const struct fb_image *image, struct fb_info *
> {
> 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 __iomem *dst;
> const u32 *tab = NULL;
> @@ -259,17 +259,23 @@ static inline void fast_imageblit(const struct fb_image *image, struct fb_info *
>
> for (i = image->height; i--; ) {
> dst = (u32 __iomem *)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) {
> FB_WRITEL(colortab[(*src >> 4) & bit_mask], dst++);
> FB_WRITEL(colortab[(*src >> 0) & bit_mask], dst++);
> }
> break;
> case 2: /* 16 bpp */
> - for (j = k; j; j -= 4, ++src) {
> + for (j = k; j >= 4; j -= 4, ++src) {
> FB_WRITEL(colortab[(*src >> 6) & bit_mask], dst++);
> FB_WRITEL(colortab[(*src >> 4) & bit_mask], dst++);
> FB_WRITEL(colortab[(*src >> 2) & bit_mask], dst++);
> @@ -277,7 +283,7 @@ static inline void fast_imageblit(const struct fb_image *image, struct fb_info *
> }
> break;
> case 1: /* 32 bpp */
> - for (j = k; j; j -= 8, ++src) {
> + for (j = k; j >= 8; j -= 8, ++src) {
> FB_WRITEL(colortab[(*src >> 7) & bit_mask], dst++);
> FB_WRITEL(colortab[(*src >> 6) & bit_mask], dst++);
> FB_WRITEL(colortab[(*src >> 5) & bit_mask], dst++);
> @@ -290,6 +296,20 @@ static inline void fast_imageblit(const struct fb_image *image, struct fb_info *
> 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;
> + FB_WRITEL(colortab[(*src >> shift) & bit_mask], dst++);
> + if (!shift) {
> + shift = 8;
> + ++src;
> + }
> + }
> +
> dst1 += p->fix.line_length;
> s += spitch;
> }
