On Tue, 25 Sep 2012 13:47:54 +0200 Daniel Vetter <daniel at ffwll.ch> wrote: > On Tue, Sep 25, 2012 at 1:08 PM, Jesse Barnes <jbarnes at virtuousgeek.org> wrote: > > On Tue, 25 Sep 2012 10:54:00 +0200 > > Daniel Vetter <daniel at ffwll.ch> wrote: > > > >> On Wed, Sep 19, 2012 at 01:28:57PM -0700, Jesse Barnes wrote: > >> > Some commands and workarounds require stores to occur to function > >> > correctly, so add some scratch space to the HWS page to accommodate > >> > them. > >> > > >> > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org> > >> > --- > >> > drivers/gpu/drm/i915/intel_ringbuffer.h | 1 + > >> > 1 file changed, 1 insertion(+) > >> > > >> > diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h > >> > index 2ea7a31..ef85742 100644 > >> > --- a/drivers/gpu/drm/i915/intel_ringbuffer.h > >> > +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h > >> > @@ -181,6 +181,7 @@ intel_read_status_page(struct intel_ring_buffer *ring, > >> > * The area from dword 0x20 to 0x3ff is available for driver usage. > >> > */ > >> > #define I915_GEM_HWS_INDEX 0x20 > >> > +#define I915_GEM_SCRATCH_INDEX 0x28 /* Some commands need a scratch store */ > >> > >> Any specific reason for using an index divisible by 8? Afaik this is an > >> index, and the hw multiplies by 4 on it's own. So looks a bit puzzling > >> when reading (since iirc only 0x21 is used anywhere else, in some dri1 > >> stuff). > > > > I got scared when I saw something about qword alignment in the docs. > > Afaik you need the qword alignment only when doing a qword write. And > iirc that only works with writes to gtt address (not status page > offsets). And for 64bit store_dw writes I remember some further > restrictions (at least on some pipes). > > One thing I wonder is whether these workarounds still work when using > a status page store dw and not a direct write to a gtt address though > ... I think they do, but we should come up with a torture test for stuff like this... -- Jesse Barnes, Intel Open Source Technology Center
