Commit 3f31a017 authored by Thomas Zimmermann's avatar Thomas Zimmermann
Browse files

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



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: default avatarThomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: default avatarJocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250328141709.217283-8-tzimmermann@suse.de
parent 58523a25

drivers/gpu/drm/drm_format_helper.c

+36 −1
Original line number Diff line number Diff line
@@ -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++)));

}