Re: [PATCH] drm/i915: Add missing rpm wakelock to GGTT pread

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On to, 2016-08-04 at 09:09 +0100, Chris Wilson wrote:
> Joonas spotted a discrepancy between the pwrite and pread ioctls, in
> that pwrite takes the rpm wakelock around its GGTT access, The wakelock
> is required in order for the GTT to function. In disregard for the
> current convention, we take the rpm wakelock around the access itself
> rather than around the struct_mutex as the nesting is not strictly
> required and such ordering will one day be fixed by explicitly noting
> the barrier dependencies between the GGTT and rpm.
> 
> Fixes: b50a53715f09 ("drm/i915: Support for pread/pwrite ...")
> Reported-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: drm-intel-fixes@lists.freedesktop.org
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 9bef2c0803a5..9cb838ef8d02 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -887,9 +887,12 @@ i915_gem_pread_ioctl(struct drm_device *dev, void *data,
>  	ret = i915_gem_shmem_pread(dev, obj, args, file);
>  
>  	/* pread for non shmem backed objects */
> -	if (ret == -EFAULT || ret == -ENODEV)
> +	if (ret == -EFAULT || ret == -ENODEV) {
> +		intel_runtime_pm_get(to_i915(dev));
>  		ret = i915_gem_gtt_pread(dev, obj, args->size,
>  					args->offset, args->data_ptr);
> +		intel_runtime_pm_put(to_i915(dev));
> +	}
>  
>  out:
>  	i915_gem_object_put(obj);
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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