Re: some stuff about controlfb in 2.2
From: Michel Lanners <hidden>
Date: 2000-08-18 19:22:18
Hi Olaf, On 18 Aug, this message from Olaf Hering echoed through cyberspace:
while trying to get xf4 to work on all machines here at suse I used this patch for the controlfb driver in a 7500/100 and 7600/132. The (basic) diff can be found on Micheals homepage.
What's on my page is really only what I needed to get it working in my case, as you have noted below...
My question is: How can we improve the support for the controlfb? The xf4 patch is needed to remove the offset problem. It is no perfect yet. 16bit does not work, colors are screwed up. 8bit has some shift to the left (proably one byte/ 8 pixels). 24bit worked fine with 832x624 on the 7500. I can not use that high colordepth on the 7600, only 2mb vram.
Geert or the other XFree 'developers' on the lost might be able to help here...
I would like to attach the mentioned kernel patch to improve performance, have no idea yet how to benchmark it.
x11perf -scroll500 For a comparison, I get around 36 scrolls/sec on my 7600 (XF4.0 at 1152 x 870 @ 24bpp), caching patch applied, with a 2.2 kernel. Without the caching patch, I get below 10 scrolls/sec.
quoted hunk
diff -urN linux-2.2.16.SuSE.orig/drivers/video/fbmem.c linux-2.2.16.SuSE/drivers/video/fbmem.c--- linux-2.2.16.SuSE.orig/drivers/video/fbmem.c Thu Aug 17 02:23:14 2000 +++ linux-2.2.16.SuSE/drivers/video/fbmem.c Fri Aug 18 11:04:46 2000@@ -577,7 +577,13 @@ pgprot_val(vma->vm_page_prot) |= _PAGE_NOCACHE_S; } #elif defined(__powerpc__) - pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE|_PAGE_GUARDED; + /* set mode for controlfb in PowerMacs + * see http://www.cpu.lu/~mlan/linux/dev/xf4.html + */ + if(find_devices("control")) + pgprot_val(vma->vm_page_prot) |= _PAGE_WRITETHRU; + else + pgprot_val(vma->vm_page_prot) |= _PAGE_NO_CACHE|_PAGE_GUARDED; #elif defined(__alpha__) /* Caching is off in the I/O space quadrant by design. */ #elif defined(__i386__)Is this patch ok for the kernel? Maybe we should `flag = find_devices("control");` to be safe.
I think the better way to handle this would be to provide a device-specific mmap function in the framebuffers that benefit from the changed caching. On Macs, all unaccelerated framebuffers should fall under that category. Or, one could also argue that _PAGE_WRITETHRU should be the default, and those framebuffers that need something else should provide that themselves. Cheers Michel ------------------------------------------------------------------------- Michel Lanners | " Read Philosophy. Study Art. 23, Rue Paul Henkes | Ask Questions. Make Mistakes. L-1710 Luxembourg | email mlan@cpu.lu | http://www.cpu.lu/~mlan | Learn Always. " ** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/