[Intel-gfx] [PATCH] drm/i915: bdw expands ACTHD to 64bit

[Chris Wilson]

On Thu, Mar 20, 2014 at 04:17:26PM +0100, Daniel Vetter wrote:
> On Thu, Mar 20, 2014 at 07:54:19AM +0000, Chris Wilson wrote:
> > On Wed, Mar 19, 2014 at 04:06:38PM -0700, Ben Widawsky wrote:
> > > On Wed, Mar 19, 2014 at 09:54:48PM +0000, Chris Wilson wrote:
> > > > As Broadwell has an increased virtual address size, it requires more
> > > > than 32 bits to store offsets into its address space. This includes the
> > > > debug registers to track the current HEAD of the individual rings, which
> > > > may be anywhere within the per-process address spaces. In order to find
> > > > the full location, we need to read the high bits from a second register.
> > > > We then also need to expand our storage to keep track of the larger
> > > > address.
> > > > 
> > > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > > Cc: Ben Widawsky <benjamin.widawsky at intel.com>
> > > > Cc: Timo Aaltonen <tjaalton at ubuntu.com>
> > > > ---
> > > >  drivers/gpu/drm/i915/i915_drv.h         |  2 +-
> > > >  drivers/gpu/drm/i915/i915_gpu_error.c   |  2 +-
> > > >  drivers/gpu/drm/i915/i915_irq.c         |  8 +++++---
> > > >  drivers/gpu/drm/i915/i915_reg.h         |  1 +
> > > >  drivers/gpu/drm/i915/intel_ringbuffer.c | 21 +++++++++++++++------
> > > >  drivers/gpu/drm/i915/intel_ringbuffer.h |  6 +++---
> > > >  6 files changed, 26 insertions(+), 14 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > > > index ed67b4abf9e3..ee913b63a945 100644
> > > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > > @@ -354,12 +354,12 @@ struct drm_i915_error_state {
> > > >  		u32 ipeir;
> > > >  		u32 ipehr;
> > > >  		u32 instdone;
> > > > -		u32 acthd;
> > > >  		u32 bbstate;
> > > >  		u32 instpm;
> > > >  		u32 instps;
> > > >  		u32 seqno;
> > > >  		u64 bbaddr;
> > > > +		u64 acthd;
> > > >  		u32 fault_reg;
> > > >  		u32 faddr;
> > > >  		u32 rc_psmi; /* sleep state */
> > > > diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
> > > > index b153a16ead0a..9519aa240614 100644
> > > > --- a/drivers/gpu/drm/i915/i915_gpu_error.c
> > > > +++ b/drivers/gpu/drm/i915/i915_gpu_error.c
> > > > @@ -248,7 +248,7 @@ static void i915_ring_error_state(struct drm_i915_error_state_buf *m,
> > > >  	err_printf(m, "  TAIL: 0x%08x\n", ring->tail);
> > > >  	err_printf(m, "  CTL: 0x%08x\n", ring->ctl);
> > > >  	err_printf(m, "  HWS: 0x%08x\n", ring->hws);
> > > > -	err_printf(m, "  ACTHD: 0x%08x\n", ring->acthd);
> > > > +	err_printf(m, "  ACTHD: 0x%08llx\n", ring->acthd);
> > > 
> > > %016x?
> > > 
> > > if (gen8)
> > > 	%016x
> > > ?
> > 
> > I wasn't sure either, but I thought since we didn't do anything special
> > for BBADDR, to leave ACTHD alone.
> > 
> > I wonder if it would help splitting it up, having to count 8 extra
> > leading zeros is going to be a nightmare (especially as the decoder
> > doesn't pad it right either...)
> > 
> > For reading, I think I would prefer
> > err_printf(m, "  ACTHD: 0x%016llx [0x%08x %08x]\n",
> >            ring->acthd, (u32)(ring->acthd>>32), (u32)(ring->acthd));
> > 
> > or maybe just
> > err_printf(m, "  ACTHD: 0x%08x %08x\n",
> >            (u32)(ring->acthd>>32), (u32)(ring->acthd));
> 
> I expect this to lead to a day-long wtf session once we have 64b ppgtt
> enabled and a leaking X hung ;-) I use g* a lot in vim when reading error
> states, so dropping information is dangerous.

I'm not following, where is the information loss? If you haven't already
guessed, we are seeing ACTHD above 4GiB already.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre