[coreboot-gerrit] Change in coreboot[master]: libpayload: cbgfx: Clear screen by sequential access

[Julius Werner (Code Review)]

Julius Werner has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/57104 )

Change subject: libpayload: cbgfx: Clear screen by sequential access
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Patch Set 5:

(1 comment)

File payloads/libpayload/drivers/video/graphics.c:

https://review.coreboot.org/c/coreboot/+/57104/comment/bc747049_7cfd29a3 
PS4, Line 637: 		memset(FB, color & 0xff, fbinfo->y_resolution * bpl);
> I think most people cannot identify the difference if we simply use #202020 or #21212121 ... […]

The problem is probably memcpy()ing out of the framebuffer, since it's likely mapped with a memory type where read accesses are slow. Something like this would probably work better:

uint8_t *line = alloca(bpl);
 for (int x = 0; x < fbinfo->x_resolution; x++)
   for (int i = 0; i < bpp / 8; i++)
     line[x * bpp + i] = color >> (i * 8);
 for (int y = 0; y < fbinfo->y_resolution; y++)
   memcpy(FB + y * bpl, line, bpl);