drm/i915: Ensure that while(INREG()) are bounded (v2)
Add a new macro, wait_for, to simplify the act of waiting on a register
to change state. wait_for() takes three arguments, the condition to
inspect on every loop, the maximum amount of time to wait and whether to
yield the cpu for a length of time after each check.
v2: Upgrade failure messages to DRM_ERROR on the suggestion of
Eric Anholt. We do not expect to hit these conditions as they reflect
programming errors, so if we do we want to be notified.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/intel_lvds.c b/drivers/gpu/drm/i915/intel_lvds.c
index cb5821e..b819c10 100644
--- a/drivers/gpu/drm/i915/intel_lvds.c
+++ b/drivers/gpu/drm/i915/intel_lvds.c
@@ -96,7 +96,7 @@
static void intel_lvds_set_power(struct drm_device *dev, bool on)
{
struct drm_i915_private *dev_priv = dev->dev_private;
- u32 pp_status, ctl_reg, status_reg, lvds_reg;
+ u32 ctl_reg, status_reg, lvds_reg;
if (HAS_PCH_SPLIT(dev)) {
ctl_reg = PCH_PP_CONTROL;
@@ -114,9 +114,8 @@
I915_WRITE(ctl_reg, I915_READ(ctl_reg) |
POWER_TARGET_ON);
- do {
- pp_status = I915_READ(status_reg);
- } while ((pp_status & PP_ON) == 0);
+ if (wait_for(I915_READ(status_reg) & PP_ON, 1000, 0))
+ DRM_ERROR("timed out waiting to enable LVDS pipe");
intel_lvds_set_backlight(dev, dev_priv->backlight_duty_cycle);
} else {
@@ -124,9 +123,8 @@
I915_WRITE(ctl_reg, I915_READ(ctl_reg) &
~POWER_TARGET_ON);
- do {
- pp_status = I915_READ(status_reg);
- } while (pp_status & PP_ON);
+ if (wait_for((I915_READ(status_reg) & PP_ON) == 0, 1000, 0))
+ DRM_ERROR("timed out waiting for LVDS pipe to turn off");
I915_WRITE(lvds_reg, I915_READ(lvds_reg) & ~LVDS_PORT_EN);
POSTING_READ(lvds_reg);