drm/i915: Add missing rpm wakelock to GGTT pread

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>
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
Link: http://patchwork.freedesktop.org/patch/msgid/1470298193-21765-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 86ff14c..03bad1b 100644 (file)
--- 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);