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>

1 files changed, 9 insertions, 16 deletions

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index cee5d9ceb3b8..c6629bd9430f 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -759,22 +759,18 @@ intel_dp_mode_set(struct drm_encoder *encoder, struct drm_display_mode *mode,
 static void ironlake_edp_panel_on (struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
-        unsigned long timeout = jiffies + msecs_to_jiffies(5000);
-        u32 pp, pp_status;
+        u32 pp;
 
-        pp_status = I915_READ(PCH_PP_STATUS);
-        if (pp_status & PP_ON)
+        if (I915_READ(PCH_PP_STATUS) & PP_ON)
                 return;
 
         pp = I915_READ(PCH_PP_CONTROL);
         pp |= PANEL_UNLOCK_REGS | POWER_TARGET_ON;
         I915_WRITE(PCH_PP_CONTROL, pp);
-        do {
-                pp_status = I915_READ(PCH_PP_STATUS);
-        } while (((pp_status & PP_ON) == 0) && !time_after(jiffies, timeout));
 
-        if (time_after(jiffies, timeout))
-                DRM_DEBUG_KMS("panel on wait timed out: 0x%08x\n", pp_status);
+        if (wait_for(I915_READ(PCH_PP_STATUS) & PP_ON, 5000, 10))
+                DRM_ERROR("panel on wait timed out: 0x%08x\n",
+                          I915_READ(PCH_PP_STATUS));
 
         pp &= ~(PANEL_UNLOCK_REGS | EDP_FORCE_VDD);
         I915_WRITE(PCH_PP_CONTROL, pp);
@@ -783,18 +779,15 @@ static void ironlake_edp_panel_on (struct drm_device *dev)
 static void ironlake_edp_panel_off (struct drm_device *dev)
 {
         struct drm_i915_private *dev_priv = dev->dev_private;
-        unsigned long timeout = jiffies + msecs_to_jiffies(5000);
-        u32 pp, pp_status;
+        u32 pp;
 
         pp = I915_READ(PCH_PP_CONTROL);
         pp &= ~POWER_TARGET_ON;
         I915_WRITE(PCH_PP_CONTROL, pp);
-        do {
-                pp_status = I915_READ(PCH_PP_STATUS);
-        } while ((pp_status & PP_ON) && !time_after(jiffies, timeout));
 
-        if (time_after(jiffies, timeout))
-                DRM_DEBUG_KMS("panel off wait timed out\n");
+        if (wait_for((I915_READ(PCH_PP_STATUS) & PP_ON) == 0, 5000, 10))
+                DRM_ERROR("panel off wait timed out: 0x%08x\n",
+                          I915_READ(PCH_PP_STATUS));
 
         /* Make sure VDD is enabled so DP AUX will work */
         pp |= EDP_FORCE_VDD;