Commit 65931bbc authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

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



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: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarJocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250328141709.217283-9-tzimmermann@suse.de
parent 3f31a017

drivers/gpu/drm/drm_format_helper.c

+20 −1
Original line number Diff line number Diff line
@@ -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++));

}