On Tue, Oct 16, 2012 at 9:11 PM, Paulo Zanoni <przanoni at gmail.com> wrote: > 2012/10/11 Jesse Barnes <jbarnes at virtuousgeek.org>: >> I've only lightly tested this so far, but the corruption seems to be >> gone if I write the GFX_FLSH_CNTL reg after binding an object. This >> register should control the TLB for the system agent, which is what CPU >> mapped objects will go through. >> >> Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org> >> >> diff --git a/drivers/char/agp/intel-agp.h b/drivers/char/agp/intel-agp.h >> index 6ec0fff..95f0d4d 100644 >> --- a/drivers/char/agp/intel-agp.h >> +++ b/drivers/char/agp/intel-agp.h >> @@ -99,6 +99,9 @@ >> #define GFX_FLSH_CNTL 0x2170 /* 915+ */ >> #define GFX_FLSH_CNTL_VLV 0x101008 >> >> +#define GFX_FLSH_CNTL 0x101008 >> +#define GFX_FLSH_CNTL_EN (1<<0) > > Notice that there's a redefinition of GFX_FLSH_CNTL with a different > value just 3 lines above. We're probably fixing gen6+ and breaking > gen5- Yeah, Jesse needs to fix up this patch (or me, since it'll conflict anyway with -fixes, so I need a backmerge first). > We write 0 to this reg in some places, but I believe that shouldn't matter. This is one of the magic registers we have: Read always returns 0, it doesn't matter what you write into it, but something special happens as a side-effect of writing to it. In this case we flush the cpu gtt tlb. We have a few others of this kind. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
