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drm/format-helper: Optimize 32-to-8-bpp conversion

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For ease of implementation, existing line-conversion functions
for 8-bit formats write each pixel individually. Optimize the
performance by writing multiple pixels in a single 32-bit store.

v2:
- simplify address calculation (Jani)
- fix typo in commit message (Jocelyn)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250328141709.217283-9-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2025-03-28 15:15:04 +01:00
parent 3f31a017dd
commit 65931bbc51
1 changed files with 20 additions and 1 deletions
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21
drivers/gpu/drm/drm_format_helper.c
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@ -253,10 +253,29 @@ static __always_inline void drm_fb_xfrm_line_32to8(void *dbuf, const void *sbuf,
unsigned int pixels,
u32 (*xfrm_pixel)(u32))
{
u8 *dbuf8 = dbuf;
__le32 *dbuf32 = dbuf;
u8 *dbuf8;
const __le32 *sbuf32 = sbuf;
const __le32 *send32 = sbuf32 + pixels;
/* write 4 pixels at once */
while (sbuf32 < ALIGN_DOWN_PIXELS(send32, pixels, 4)) {
u32 pix[4] = {
le32_to_cpup(sbuf32++),
le32_to_cpup(sbuf32++),
le32_to_cpup(sbuf32++),
le32_to_cpup(sbuf32++),
};
/* write output bytes in reverse order for little endianness */
u32 val32 = xfrm_pixel(pix[0]) |
(xfrm_pixel(pix[1]) << 8) |
(xfrm_pixel(pix[2]) << 16) |
(xfrm_pixel(pix[3]) << 24);
*dbuf32++ = cpu_to_le32(val32);
}
/* write trailing pixels */
dbuf8 = (u8 __force *)dbuf32;
while (sbuf32 < send32)
*dbuf8++ = xfrm_pixel(le32_to_cpup(sbuf32++));
}