[Intel-gfx] [PATCH 1/6] drm/i915: Get runtime pm ref on i915_drop_caches_set

Chris Wilson chris at chris-wilson.co.uk
Mon Dec 14 13:46:34 PST 2015

On Mon, Dec 14, 2015 at 07:14:23PM +0200, Mika Kuoppala wrote:
> When we drop caches, this debugfs entry does hardware access later in
> the chain, when fences are updated, so it needs a runtime pm ref.
> Dropping caches is used by some igt/bat tests, so this fixes
> some unclaimed register access traces.
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c | 3 +++
>  1 file changed, 3 insertions(+)
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index 24318b7..bd8ba7e 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -4839,6 +4839,8 @@ i915_drop_caches_set(void *data, u64 val)
>  	if (ret)
>  		return ret;
> +	intel_runtime_pm_get(dev_priv);

The current idea of the very coarse granularity of rpm_get() is to do it
before struct_mutex (since rpm_get resume may try to acquire the mutex

Ok, fixing that may be bolting the stable door after the horse bolted,
but we should nevertheless. In my opinion, it would be more productive
to work with Imre on making rpm fine grained so that we don't so many
and can actually place the wakelock around the hardware access itself,
not every single path that *may* touch hardware.

Chris Wilson, Intel Open Source Technology Centre

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