Hi Michael, CC linux-m68k
On Sun, 6 Sept 2026 at 03:49, Michael Schmitz <[email protected]> wrote: > Am 27.08.2026 um 21:39 schrieb Linmao Li: > > The SuperBlitter operations derive an integer byte count per pixel. The > > accelerated fill path handles only one-, two- and four-byte pixels. > > However, the operations are currently installed for every external > > framebuffer in SuperVidel RAM, including planar 1/2/4/8-bpp and 24-bpp > > truecolor modes accepted by the external video parser. > > > > For 1/2/4-bpp modes, the byte count becomes zero, so accelerated copies do > > nothing and fills fall through to 32-bit stores. Planar 8-bpp uses an > > incompatible memory layout. For 24-bpp modes, fills also use 32-bit stores > > despite advancing addresses by three bytes per pixel. These cases can > > corrupt the framebuffer beyond the requested rectangle. > > I believe 24 bpp mode can be rescued using something like this (entirely > untested): > > --- a/drivers/video/fbdev/atafb.c > +++ b/drivers/video/fbdev/atafb.c > @@ -2463,6 +2463,11 @@ static void svblit_fillrect(struct fb_info *info, > case 2: > memset16((u16 *)line, pix, rect->width); > break; > + case 3: > + memset(line, pix, ((rect->width * bytespp) % 4)); > + line += ((rect->width * bytespp) % 4); > + memset32((u32 *)line, pix, (rect->width * bytespp) / 4); This uses unaligned writes for the largest part. You can avoid that by doing the memset32() first. > + break; > default: > memset32((u32 *)line, pix, rect->width); > break; > > Can't test this on hardware, and would need Miro to confirm it works as > intended. > > > > > Enable the SuperBlitter operations only for the layouts they implement: > > 8-bpp packed pixels and 16/32-bpp truecolor. Keep the existing software > > operations for all other external formats. > > > > Fixes: d463633d63e6 ("fbdev: atafb: Add support for SuperVidel's > > SuperBlitter") > > Signed-off-by: Linmao Li <[email protected]> > > --- > > drivers/video/fbdev/atafb.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/video/fbdev/atafb.c b/drivers/video/fbdev/atafb.c > > index 5bca34c45cef3..c3011b61a94b9 100644 > > --- a/drivers/video/fbdev/atafb.c > > +++ b/drivers/video/fbdev/atafb.c > > @@ -3360,7 +3360,11 @@ static int __init atafb_probe(struct platform_device > > *pdev) > > memset (screen_base, 0, external_len); > > > > /* framebuffer in SV RAM: enable the SuperBlitter */ > > - if (external_addr >= 0xa0000000) { > > + if (external_addr >= 0xa0000000 && > > + ((external_pmode == FB_TYPE_PACKED_PIXELS && > > + external_depth == 8) || > > + (external_pmode == -1 && > > + (external_depth == 16 || external_depth == 32)))) { > > svblit_regs = ioremap(SVBLIT_REGS_PHYS, 0x100); > > if (svblit_regs) { > > svblit_fw = svblit_rd(SVBLIT_VERSION) & 0x1ff; > > > > Otherwise, LGTM. > > @Geert: can you remember if pixel format or bit depth of an external > framebuffer can be changed at runtime using fbset?? I am no Atari expert, but IIRC all external framebuffers rely on being fully set-up before Linux boots? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected] In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
