[PATCH] drm/i915: enable the power well before module unload

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

Our driver initialization doesn't seem to be ready to load when the
power well is disabled: we hit a few "Unclaimed register" messages. So
do just like we already do for the suspend/resume path: enable the
power well before unloading.

At some point we'll want to be able to survive suspend/resume and
load/unload with the power well disabled, but for now let's just fix
the regression.

Regression introduced by the following commit:

commit bf51d5e2cda5d36d98e4b46ac7fca9461e512c41
Author: Paulo Zanoni <paulo.r.zanoni@intel.com>
Date:   Wed Jul 3 17:12:13 2013 -0300
    drm/i915: switch disable_power_well default value to 1

Bug can be reproduced by running the "module_reload" script from
intel-gpu-tools.

Cc: stable@vger.kernel.org
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=67813
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/i915_dma.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)


QA (the bug reporter) still didn't confirm this patch fixes the bug, but I can
reproduce it and I can confirm it fixes the problem at least on my machine.

Also please notice we have other problems that happen when we run module_reload
(e.g., gpu hang, no backlight, lockdep error message, eventual oops), this patch
fixes only the "Unclaimed register" errors.

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index b30404d..d2dc02b 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1688,8 +1688,13 @@ int i915_driver_unload(struct drm_device *dev)
 
 	intel_gpu_ips_teardown();
 
-	if (HAS_POWER_WELL(dev))
+	if (HAS_POWER_WELL(dev)) {
+		/* The i915.ko module is still not prepared to be loaded when
+		 * the power well is not enabled, so just enable it in case
+		 * we're going to unload/reload. */
+		intel_set_power_well(dev, true);
 		i915_remove_power_well(dev);
+	}
 
 	i915_teardown_sysfs(dev);
 
-- 
1.8.1.2