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drm/format-helper: Optimize 32-to-16-bpp conversion

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For ease of implementation, existing line-conversion functions
for 16-bit formats write each pixel individually. Optimize the
performance by writing multiple pixels in single 64-bit and 32-bit
stores.

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/20250328141709.217283-8-tzimmermann@suse.de
This commit is contained in:
Thomas Zimmermann 2025-03-28 15:15:03 +01:00
parent 58523a25cb
commit 3f31a017dd
1 changed files with 36 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

37
drivers/gpu/drm/drm_format_helper.c
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@ -265,10 +265,45 @@ static __always_inline void drm_fb_xfrm_line_32to16(void *dbuf, const void *sbuf
unsigned int pixels,
u32 (*xfrm_pixel)(u32))
{
__le16 *dbuf16 = dbuf;
__le64 *dbuf64 = dbuf;
__le32 *dbuf32;
__le16 *dbuf16;
const __le32 *sbuf32 = sbuf;
const __le32 *send32 = sbuf32 + pixels;
#if defined(CONFIG_64BIT)
/* 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 */
u64 val64 = ((u64)xfrm_pixel(pix[0])) |
((u64)xfrm_pixel(pix[1]) << 16) |
((u64)xfrm_pixel(pix[2]) << 32) |
((u64)xfrm_pixel(pix[3]) << 48);
*dbuf64++ = cpu_to_le64(val64);
}
#endif
/* write 2 pixels at once */
dbuf32 = (__le32 __force *)dbuf64;
while (sbuf32 < ALIGN_DOWN_PIXELS(send32, pixels, 2)) {
u32 pix[2] = {
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]) << 16);
*dbuf32++ = cpu_to_le32(val32);
}
/* write trailing pixel */
dbuf16 = (__le16 __force *)dbuf32;
while (sbuf32 < send32)
*dbuf16++ = cpu_to_le16(xfrm_pixel(le32_to_cpup(sbuf32++)));
}