Commit 58523a25 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

drm/format-helper: Optimize 32-to-24-bpp conversion 



For ease of implementation, existing line-conversion functions
for 24-bit formats write each byte individually. Optimize the
performance by writing 4 pixels in 3 32-bit stores.

v2:
- simplify address calculation (Jani)

Signed-off-by: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarJocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250328141709.217283-7-tzimmermann@suse.de
parent a376dcf4

drivers/gpu/drm/drm_format_helper.c

+36 −1
Original line number Diff line number Diff line
@@ -246,6 +246,9 @@ static int drm_fb_xfrm(struct iosys_map *dst, 
				     xfrm_line);

}



#define ALIGN_DOWN_PIXELS(end, n, a) \

	((end) - ((n) & ((a) - 1)))



static __always_inline void drm_fb_xfrm_line_32to8(void *dbuf, const void *sbuf,

						   unsigned int pixels,

						   u32 (*xfrm_pixel)(u32))
@@ -274,10 +277,42 @@ static __always_inline void drm_fb_xfrm_line_32to24(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 pixels in chunks of 4 */

	while (sbuf32 < ALIGN_DOWN_PIXELS(send32, pixels, 4)) {

		u32 val24[4] = {

			xfrm_pixel(le32_to_cpup(sbuf32++)),

			xfrm_pixel(le32_to_cpup(sbuf32++)),

			xfrm_pixel(le32_to_cpup(sbuf32++)),

			xfrm_pixel(le32_to_cpup(sbuf32++)),

		};

		u32 out32[3] = {

			/* write output bytes in reverse order for little endianness */

			((val24[0] & 0x000000ff)) |

			((val24[0] & 0x0000ff00)) |

			((val24[0] & 0x00ff0000)) |

			((val24[1] & 0x000000ff) << 24),

			((val24[1] & 0x0000ff00) >> 8) |

			((val24[1] & 0x00ff0000) >> 8) |

			((val24[2] & 0x000000ff) << 16) |

			((val24[2] & 0x0000ff00) << 16),

			((val24[2] & 0x00ff0000) >> 16) |

			((val24[3] & 0x000000ff) << 8) |

			((val24[3] & 0x0000ff00) << 8) |

			((val24[3] & 0x00ff0000) << 8),

		};



		*dbuf32++ = cpu_to_le32(out32[0]);

		*dbuf32++ = cpu_to_le32(out32[1]);

		*dbuf32++ = cpu_to_le32(out32[2]);

	}



	/* write trailing pixel */

	dbuf8 = (u8 __force *)dbuf32;

	while (sbuf32 < send32) {

		u32 val24 = xfrm_pixel(le32_to_cpup(sbuf32++));

		/* write output in reverse order for little endianness */