[Intel-gfx] [PATCH] drm/i915: Add missing rpm wakelock to GGTT pread

[Chris Wilson]

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 at linux.intel.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ankitprasad Sharma <ankitprasad.r.sharma at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
Cc: drm-intel-fixes at 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);
-- 
2.8.1