Re: [PATCH 06/15] drm/i915/selftests: Check known register values within the context

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 14/10/2019 10:07, Chris Wilson wrote:
> Check the logical ring context by asserting that the registers hold
> expected start during execution. (It's a bit chicken-and-egg for how
> could we manage to execute our request if the registers were not being
> updated. Still, it's nice to verify that the HW is working as expected.)
> 
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> ---
>   drivers/gpu/drm/i915/gt/selftest_lrc.c | 126 +++++++++++++++++++++++++
>   1 file changed, 126 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index a691e429ca01..0aa36b1b2389 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -2599,10 +2599,136 @@ static int live_lrc_layout(void *arg)
>   	return err;
>   }
>   
> +static int __live_lrc_state(struct i915_gem_context *fixme,
> +			    struct intel_engine_cs *engine,
> +			    struct i915_vma *scratch)
> +{
> +	struct intel_context *ce;
> +	struct i915_request *rq;
> +	enum {
> +		RING_START_IDX = 0,
> +		RING_TAIL_IDX,
> +		MAX_IDX
> +	};
> +	u32 expected[MAX_IDX];
> +	u32 *cs;
> +	int err;
> +	int n;
> +
> +	ce = intel_context_create(fixme, engine);

Calling the context fixme imo just makes the code less readable.

> +	if (IS_ERR(ce))
> +		return PTR_ERR(ce);
> +
> +	err = intel_context_pin(ce);
> +	if (err)
> +		goto err_put;
> +
> +	rq = i915_request_create(ce);
> +	if (IS_ERR(rq)) {
> +		err = PTR_ERR(rq);
> +		goto err_unpin;
> +	}
> +
> +	cs = intel_ring_begin(rq, 4 * MAX_IDX);
> +	if (IS_ERR(cs)) {
> +		err = PTR_ERR(cs);
> +		i915_request_add(rq);
> +		goto err_unpin;
> +	}
> +
> +	*cs++ = MI_STORE_REGISTER_MEM_GEN8 | MI_USE_GGTT;
> +	*cs++ = i915_mmio_reg_offset(RING_START(engine->mmio_base));
> +	*cs++ = i915_ggtt_offset(scratch) + RING_START_IDX * sizeof(u32);
> +	*cs++ = 0;
> +
> +	expected[RING_START_IDX] = i915_ggtt_offset(ce->ring->vma);
> +
> +	*cs++ = MI_STORE_REGISTER_MEM_GEN8 | MI_USE_GGTT;
> +	*cs++ = i915_mmio_reg_offset(RING_TAIL(engine->mmio_base));
> +	*cs++ = i915_ggtt_offset(scratch) + RING_TAIL_IDX * sizeof(u32);
> +	*cs++ = 0;
> +
> +	i915_request_get(rq);
> +	i915_request_add(rq);
> +
> +	intel_engine_flush_submission(engine);
> +	expected[RING_TAIL_IDX] = ce->ring->tail;
> +
> +	if (i915_request_wait(rq, 0, HZ / 5) < 0) {
> +		err = -ETIME;
> +		goto err_rq;
> +	}
> +
> +	cs = i915_gem_object_pin_map(scratch->obj, I915_MAP_WB);
> +	if (IS_ERR(cs)) {
> +		err = PTR_ERR(cs);
> +		goto err_rq;
> +	}
> +
> +	for (n = 0; n < MAX_IDX; n++) {
> +		if (cs[n] != expected[n]) {
> +			pr_err("%s: Stored register[%d] value[0x%x] did not match expected[0x%x]\n",
> +			       engine->name, n, cs[n], expected[n]);
> +			err = -EINVAL;
> +			break;
> +		}
> +	}
> +
> +	i915_gem_object_unpin_map(scratch->obj);
> +
> +err_rq:
> +	i915_request_put(rq);
> +err_unpin:
> +	intel_context_unpin(ce);
> +err_put:
> +	intel_context_put(ce);
> +	return err;
> +}
> +
> +static int live_lrc_state(void *arg)
> +{
> +	struct intel_gt *gt = arg;
> +	struct intel_engine_cs *engine;
> +	struct i915_gem_context *fixme;
> +	struct i915_vma *scratch;
> +	enum intel_engine_id id;
> +	int err = 0;
> +
> +	/*
> +	 * Check the live register state matches what we expect for this
> +	 * intel_context.
> +	 */
> +
> +	fixme = kernel_context(gt->i915);
> +	if (!fixme)
> +		return -ENOMEM;
> +
> +	scratch = create_scratch(gt);
> +	if (IS_ERR(scratch)) {
> +		err = PTR_ERR(scratch);
> +		goto out_close;
> +	}
> +
> +	for_each_engine(engine, gt->i915, id) {
> +		err = __live_lrc_state(fixme, engine, scratch);
> +		if (err)
> +			break;
> +	}
> +
> +	if (igt_flush_test(gt->i915))
> +		err = -EIO;
> +
> +	i915_vma_unpin_and_release(&scratch, 0);
> +out_close:
> +	kernel_context_close(fixme);
> +	return err;
> +}
> +
>   int intel_lrc_live_selftests(struct drm_i915_private *i915)
>   {
>   	static const struct i915_subtest tests[] = {
>   		SUBTEST(live_lrc_layout),
> +		SUBTEST(live_lrc_state),
>   	};
>   
>   	if (!HAS_LOGICAL_RING_CONTEXTS(i915))
> 

I don't know.. guess it has some extra value compared to basic MI_NOOP 
tests.

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Regards,

Tvrtko
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