[Intel-gfx] [PATCH] drm/i915/pmu: Wait longer for busyness data to be available from GuC

[Matthew Brost]

On Tue, Dec 07, 2021 at 06:15:12PM -0800, Umesh Nerlige Ramappa wrote:
> live_engine_busy_stats waits for busyness to start ticking before
> sampling busyness for the test sample duration. The wait accesses an
> MMIO register and the uncore call to read it takes up to 3 ms in the
> worst case. This can result in the wait timing out since the MMIO read
> itself comsumes up the timeout of 500us. Increase the timeout to a
> larger value of 10ms to account for the MMIO read time.
> 
> Resolves: https://gitlab.freedesktop.org/drm/intel/-/issues/4536

With 's/Resolves/Closes' per Jani's feedback:

Reviewed-by: Matthew Brost <matthew.brost at intel.com>
> Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa at intel.com>
> ---
>  drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
> index 75f6efc9882f..8af261831470 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_engine_pm.c
> @@ -229,7 +229,7 @@ static int __spin_until_busier(struct intel_engine_cs *engine, ktime_t busyness)
>  	start = ktime_get();
>  	while (intel_engine_get_busy_time(engine, &unused) == busyness) {
>  		dt = ktime_get() - start;
> -		if (dt > 500000) {
> +		if (dt > 10000000) {
>  			pr_err("active wait timed out %lld\n", dt);
>  			ENGINE_TRACE(engine, "active wait time out %lld\n", dt);
>  			return -ETIME;
> -- 
> 2.20.1
>