Hi Rodrigo,
On Mon, Dec 12, 2022 at 11:55:10AM -0500, Rodrigo Vivi wrote:
> On Mon, Dec 12, 2022 at 05:13:38PM +0100, Andi Shyti wrote:
> > From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> >
> > After applying an engine reset, on some platforms like Jasperlake, we
> > occasionally detect that the engine state is not cleared until shortly
> > after the resume. As we try to resume the engine with volatile internal
> > state, the first request fails with a spurious CS event (it looks like
> > it reports a lite-restore to the hung context, instead of the expected
> > idle->active context switch).
> >
> > Signed-off-by: Chris Wilson <hris@xxxxxxxxxxxxxxxxxx>
>
> There's a typo in the signature email I'm afraid...
oh yes, I forgot the 'C' :)
> Other than that, have we checked the possibility of using the driver-initiated-flr bit
> instead of this second loop? That should be the right way to guarantee everything is
> cleared on gen11+...
maybe I am misinterpreting it, but is FLR the same as resetting
hardware domains individually?
How am I supposed to use driver_initiated_flr() in this context?
Thanks,
Andi
> > Cc: stable@xxxxxxxxxxxxxxx
> > Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> > Signed-off-by: Andi Shyti <andi.shyti@xxxxxxxxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/gt/intel_reset.c | 34 ++++++++++++++++++++++-----
> > 1 file changed, 28 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/intel_reset.c b/drivers/gpu/drm/i915/gt/intel_reset.c
> > index ffde89c5835a4..88dfc0c5316ff 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_reset.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_reset.c
> > @@ -268,6 +268,7 @@ static int ilk_do_reset(struct intel_gt *gt, intel_engine_mask_t engine_mask,
> > static int gen6_hw_domain_reset(struct intel_gt *gt, u32 hw_domain_mask)
> > {
> > struct intel_uncore *uncore = gt->uncore;
> > + int loops = 2;
> > int err;
> >
> > /*
> > @@ -275,18 +276,39 @@ static int gen6_hw_domain_reset(struct intel_gt *gt, u32 hw_domain_mask)
> > * for fifo space for the write or forcewake the chip for
> > * the read
> > */
> > - intel_uncore_write_fw(uncore, GEN6_GDRST, hw_domain_mask);
> > + do {
> > + intel_uncore_write_fw(uncore, GEN6_GDRST, hw_domain_mask);
> >
> > - /* Wait for the device to ack the reset requests */
> > - err = __intel_wait_for_register_fw(uncore,
> > - GEN6_GDRST, hw_domain_mask, 0,
> > - 500, 0,
> > - NULL);
> > + /*
> > + * Wait for the device to ack the reset requests.
> > + *
> > + * On some platforms, e.g. Jasperlake, we see see that the
> > + * engine register state is not cleared until shortly after
> > + * GDRST reports completion, causing a failure as we try
> > + * to immediately resume while the internal state is still
> > + * in flux. If we immediately repeat the reset, the second
> > + * reset appears to serialise with the first, and since
> > + * it is a no-op, the registers should retain their reset
> > + * value. However, there is still a concern that upon
> > + * leaving the second reset, the internal engine state
> > + * is still in flux and not ready for resuming.
> > + */
> > + err = __intel_wait_for_register_fw(uncore, GEN6_GDRST,
> > + hw_domain_mask, 0,
> > + 2000, 0,
> > + NULL);
> > + } while (err == 0 && --loops);
> > if (err)
> > GT_TRACE(gt,
> > "Wait for 0x%08x engines reset failed\n",
> > hw_domain_mask);
> >
> > + /*
> > + * As we have observed that the engine state is still volatile
> > + * after GDRST is acked, impose a small delay to let everything settle.
> > + */
> > + udelay(50);
> > +
> > return err;
> > }
> >
> > --
> > 2.38.1
> >
