Quoting Mika Kuoppala (2018-08-10 15:00:36)
> If engine reports that it is not ready for reset, we
> give up. Evidence shows that forcing a per engine reset
> on an engine which is not reporting to be ready for reset,
> can bring it back into a working order. There is risk that
> we corrupt the context image currently executing on that
> engine. But that is a risk worth taking as if we unblock
> the engine, we prevent a whole device wedging in a case
> of full gpu reset.
>
> Reset individual engine even if it reports that it is not
> prepared for reset, but only if we aim for full gpu reset
> and not on first reset attempt.
>
> v2: force reset only on later attempts, readability (Chris)
>
> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_uncore.c | 49 +++++++++++++++++++++++------
> 1 file changed, 39 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> index 027d14574bfa..d24026839b17 100644
> --- a/drivers/gpu/drm/i915/intel_uncore.c
> +++ b/drivers/gpu/drm/i915/intel_uncore.c
> @@ -2099,9 +2099,6 @@ static int gen8_reset_engine_start(struct intel_engine_cs *engine)
> RESET_CTL_READY_TO_RESET,
> 700, 0,
> NULL);
> - if (ret)
> - DRM_ERROR("%s: reset request timeout\n", engine->name);
> -
> return ret;
> }
>
> @@ -2113,6 +2110,42 @@ static void gen8_reset_engine_cancel(struct intel_engine_cs *engine)
> _MASKED_BIT_DISABLE(RESET_CTL_REQUEST_RESET));
> }
>
> +static int reset_engines(struct drm_i915_private *i915,
> + unsigned int engine_mask,
> + unsigned int retry)
> +{
> + if (INTEL_GEN(i915) >= 11)
> + return gen11_reset_engines(i915, engine_mask);
> + else
> + return gen6_reset_engines(i915, engine_mask, retry);
> +}
> +
> +static int gen8_prepare_engine_for_reset(struct intel_engine_cs *engine,
> + unsigned int retry)
> +{
> + const bool force_reset_on_non_ready = retry >= 1;
> + int ret;
> +
> + ret = gen8_reset_engine_start(engine);
> +
> + if (ret && force_reset_on_non_ready) {
> + /*
> + * Try to unblock a single non-ready engine by risking
> + * context corruption.
> + */
> + ret = reset_engines(engine->i915,
> + intel_engine_flag(engine),
> + retry);
> + if (!ret)
> + ret = gen8_reset_engine_start(engine);
> +
> + DRM_ERROR("%s: reset request timeout, forcing reset (%d)\n",
> + engine->name, ret);
This looks dubious now ;)
After the force you then do a reset in the caller. Twice the reset for
twice the unpreparedness.
> + }
> +
> + return ret;
> +}
> +
> static int gen8_reset_engines(struct drm_i915_private *dev_priv,
> unsigned int engine_mask,
> unsigned int retry)
> @@ -2122,16 +2155,12 @@ static int gen8_reset_engines(struct drm_i915_private *dev_priv,
> int ret;
>
> for_each_engine_masked(engine, dev_priv, engine_mask, tmp) {
> - if (gen8_reset_engine_start(engine)) {
> - ret = -EIO;
> + ret = gen8_prepare_engine_for_reset(engine, retry);
> + if (ret)
if (ret && !force_reset_unread)
> goto not_ready;
> - }
> }
>
> - if (INTEL_GEN(dev_priv) >= 11)
> - ret = gen11_reset_engines(dev_priv, engine_mask);
> - else
> - ret = gen6_reset_engines(dev_priv, engine_mask, retry);
> + ret = reset_engines(dev_priv, engine_mask, retry);
>
> not_ready:
> for_each_engine_masked(engine, dev_priv, engine_mask, tmp)
> --
> 2.17.1
>
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