drm/i915: Hold gt_lock across forcewake register reads

Along with the previous patch to make the reset operation protected by
the gt_lock as well, this ensures that all register read operations
will occur with the forcewake hardware enabled. As an added bonus,
this makes read operations more efficient by taking the spinlock only
once per read instead of twice.

Signed-off-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
index 062d1d27f704231e3334d21e1316bc63fbe27a2f..308f819135626c6b9c8d3805c953bd7a9ddf55dc 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.c
+++ b/drivers/gpu/drm/i915/i915_drv.c
@@ -954,9 +954,14 @@ MODULE_LICENSE("GPL and additional rights");
 u##x i915_read##x(struct drm_i915_private *dev_priv, u32 reg) { \
        u##x val = 0; \
        if (NEEDS_FORCE_WAKE((dev_priv), (reg))) { \
-               gen6_gt_force_wake_get(dev_priv); \
+               unsigned long irqflags; \
+               spin_lock_irqsave(&dev_priv->gt_lock, irqflags); \
+               if (dev_priv->forcewake_count == 0) \
+                       dev_priv->display.force_wake_get(dev_priv); \
                val = read##y(dev_priv->regs + reg); \
-               gen6_gt_force_wake_put(dev_priv); \
+               if (dev_priv->forcewake_count == 0) \
+                       dev_priv->display.force_wake_put(dev_priv); \
+               spin_unlock_irqrestore(&dev_priv->gt_lock, irqflags); \
        } else { \
                val = read##y(dev_priv->regs + reg); \
        } \