drm/i915: Clean up multi-threaded forcewake patch

commit c7dffff7cc8de748edf0e9f6571cdabecb198705 upstream.

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>
[bwh: Backported to 3.2: I previously backported a change to
 NEEDS_FORCE_WAKE() and applied it to the version in i915_drv.c, the one
 that was actually being used.  Move that change to i915_drv.h now.]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index e216c21..ba62ada 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -971,13 +971,6 @@ MODULE_AUTHOR(DRIVER_AUTHOR);
 MODULE_DESCRIPTION(DRIVER_DESC);
 MODULE_LICENSE("GPL and additional rights");
 
-/* We give fast paths for the really cool registers */
-#define NEEDS_FORCE_WAKE(dev_priv, reg) \
-       ((HAS_FORCE_WAKE((dev_priv)->dev)) && \
-        ((reg) < 0x40000) &&            \
-        ((reg) != FORCEWAKE) &&         \
-        ((reg) != ECOBUS))
-
 #define __i915_read(x, y) \
 u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \
        u##x val = 0; \

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 61274bf..783153a 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1369,10 +1369,9 @@ void __gen6_gt_wait_for_fifo(struct drm_i915_private *dev_priv);
 
 /* We give fast paths for the really cool registers */
 #define NEEDS_FORCE_WAKE(dev_priv, reg) \
-       (((dev_priv)->info->gen >= 6) && \
+       ((HAS_FORCE_WAKE((dev_priv)->dev)) && \
         ((reg) < 0x40000) &&            \
-        ((reg) != FORCEWAKE) &&         \
-        ((reg) != ECOBUS))
+        ((reg) != FORCEWAKE))
 
 #define __i915_read(x, y) \
        u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg);

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index c7b5428..4a7d597 100644 (file)
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -8699,9 +8699,15 @@ static void intel_init_display(struct drm_device *dev)
                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);