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Subject[ 75/99] Partially revert "drm/i915: unconditionally use mt forcewake on hsw/ivb"
Date
3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Guenter Roeck <linux@roeck-us.net>

commit c11e5f35ab490bd30591563816fbc83526521777 upstream.

This patch partially reverts commit 36ec8f877481449bdfa072e6adf2060869e2b970 for
IvyBridge CPUs.

The original commit results in repeated 'Timed out waiting for forcewake old
ack to clear' messages on a Supermicro C7H61 board (BIOS version 2.00 and 2.00b)
with i7-3770K CPU. It ultimately results in a hangup if the system is highly
loaded. Reverting the commit for IvyBridge CPUs fixes the issue.

Issue a warning if the CPU is IvyBridge and mt forcewake is disabled, since
this condition can result in secondary issues.

v2: Only revert patch for Ivybridge CPUs
Issue info message if mt forcewake is disabled on Ivybridge

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=60541
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=66139
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/i915/intel_pm.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -4510,9 +4510,38 @@ void intel_gt_init(struct drm_device *de
if (IS_VALLEYVIEW(dev)) {
dev_priv->gt.force_wake_get = vlv_force_wake_get;
dev_priv->gt.force_wake_put = vlv_force_wake_put;
- } else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev)) {
+ } else if (IS_HASWELL(dev)) {
dev_priv->gt.force_wake_get = __gen6_gt_force_wake_mt_get;
dev_priv->gt.force_wake_put = __gen6_gt_force_wake_mt_put;
+ } else if (IS_IVYBRIDGE(dev)) {
+ u32 ecobus;
+
+ /* IVB configs may use multi-threaded forcewake */
+
+ /* 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_NOTRACE(ECOBUS);
+ __gen6_gt_force_wake_mt_put(dev_priv);
+ mutex_unlock(&dev->struct_mutex);
+
+ if (ecobus & FORCEWAKE_MT_ENABLE) {
+ dev_priv->gt.force_wake_get =
+ __gen6_gt_force_wake_mt_get;
+ dev_priv->gt.force_wake_put =
+ __gen6_gt_force_wake_mt_put;
+ } else {
+ DRM_INFO("No MT forcewake available on Ivybridge, this can result in issues\n");
+ DRM_INFO("when using vblank-synced partial screen updates.\n");
+ dev_priv->gt.force_wake_get = __gen6_gt_force_wake_get;
+ dev_priv->gt.force_wake_put = __gen6_gt_force_wake_put;
+ }
} else if (IS_GEN6(dev)) {
dev_priv->gt.force_wake_get = __gen6_gt_force_wake_get;
dev_priv->gt.force_wake_put = __gen6_gt_force_wake_put;



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