drm/i915: Clean up multi-threaded forcewake patch
We learned that the ECOBUS register was inside the GT power well, and
so *did* need force wake to be read, so it gets removed from the list
of 'doesn't need force wake' registers.
That means the code reading ECOBUS after forcing the mt_force_wake
function to be called needs to use I915_READ_NOTRACE; it doesn't need
to do more force wake fun as it's already done it manually.
This also adds a comment explaining why the MT forcewake testing code
only needs to call mt_forcewake_get/put and not disable RC6 manually
-- the ECOBUS read will return 0 if the device is in RC6 and isn't
using MT forcewake, causing the test to work correctly.
Signed-off-by: Keith Packard <keithp@keithp.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index cb21d5b..ff99fa2 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8591,9 +8591,15 @@
if (IS_IVYBRIDGE(dev)) {
u32 ecobus;
+ /* A small trick here - if the bios hasn't configured MT forcewake,
+ * and if the device is in RC6, then force_wake_mt_get will not wake
+ * the device and the ECOBUS read will return zero. Which will be
+ * (correctly) interpreted by the test below as MT forcewake being
+ * disabled.
+ */
mutex_lock(&dev->struct_mutex);
__gen6_gt_force_wake_mt_get(dev_priv);
- ecobus = I915_READ(ECOBUS);
+ ecobus = I915_READ_NOTRACE(ECOBUS);
__gen6_gt_force_wake_mt_put(dev_priv);
mutex_unlock(&dev->struct_mutex);