On 13.03.2022 20:29, 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 <tzimmerm...@suse.de>
> Fixes: 0d03011894d2 ("fbdev: Improve performance of cfb_imageblit()")
> Reported-by: Marek Szyprowski <m.szyprow...@samsung.com>
> Cc: Thomas Zimmermann <tzimmerm...@suse.de>
> Cc: Javier Martinez Canillas <javi...@redhat.com>
> Cc: Sam Ravnborg <s...@ravnborg.org>
Tested-by: Marek Szyprowski <m.szyprow...@samsung.com>
> ---
>   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;
>       }

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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