Re: PowerPC radeon KMS - is it possible?
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2012-04-18 11:19:16
Possibly related (same subject, not in this thread)
- 2012-04-24 · Re: PowerPC radeon KMS - is it possible? · Gerhard Pircher <hidden>
- 2012-04-24 · Re: PowerPC radeon KMS - is it possible? · Michel Dänzer <hidden>
- 2012-04-23 · Re: PowerPC radeon KMS - is it possible? · Gerhard Pircher <hidden>
- 2012-04-23 · Re: PowerPC radeon KMS - is it possible? · Michel Dänzer <hidden>
- 2012-04-20 · Re: PowerPC radeon KMS - is it possible? · Gerhard Pircher <hidden>
On Wed, 2012-04-18 at 12:44 +0200, Michel Dänzer wrote:
On Mit, 2012-04-18 at 12:34 +0200, Michel Dänzer wrote:quoted
On Mit, 2012-04-18 at 20:20 +1000, Benjamin Herrenschmidt wrote:quoted
I suspect there's a fundamental design issue with apple bridge in that the CPU to memory path isn't coherent at all with the GPU to memory path ie. even vs. cache flush instructions (ie buffers in the memory controllers can still be out of sync). Darwin does some gross hacks to work around that, some of them visible in the AGP drivers, some burried in the Apple driver, I don't know for sure. It's possible that they end up mapping all AGP memory as cache inhibited, but we can't do that because of our linear mapping.We are doing that though...This reminded me, I've been running with the patch below, but I'm not sure it makes any difference. Maybe Andreas or Jordan can try it.
It certainly is something we need to do, provided we also know there will be no subsequent access to that page via a cachable mapping until it's removed from AGP. Cheers, Ben.
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/include/asm/agp.h b/arch/powerpc/include/asm/agp.h index 416e12c..eb34fa5 100644 --- a/arch/powerpc/include/asm/agp.h +++ b/arch/powerpc/include/asm/agp.h@@ -2,9 +2,12 @@ #define _ASM_POWERPC_AGP_H #ifdef __KERNEL__ +#include <asm/cacheflush.h> #include <asm/io.h> -#define map_page_into_agp(page) +#define map_page_into_agp(page) \ + flush_dcache_range((unsigned long)page_address(page), \ + (unsigned long)page_address(page) + PAGE_SIZE) #define unmap_page_from_agp(page) #define flush_agp_cache() mb()