Jesse mentioned that we had reports of flickering due to switching
clocks for powersaving and that would be a useful task to be run at
vblank.

TODO: The modification of DPLL requires some guards to prevent concurrent
access during vblank and modeset. Flushing the vblank handler before
modeset sounds like the safest approach.

<Find some testers>
---
 drivers/gpu/drm/i915/intel_display.c |  102 ++++++++++++++++++----------------
 1 files changed, 55 insertions(+), 47 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 6c2101e..2d96394 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2240,7 +2240,6 @@ intel_pipe_set_base_atomic(struct drm_crtc *crtc, struct 
drm_framebuffer *fb,
                return ret;
 
        intel_update_fbc(dev);
-       intel_increase_pllclock(crtc);
 
        return 0;
 }
@@ -2319,6 +2318,7 @@ intel_pipe_set_base(struct drm_crtc *crtc, int x, int y,
 
        mutex_unlock(&dev->struct_mutex);
 
+       intel_increase_pllclock(crtc);
        if (!dev->primary->master)
                return 0;
 
@@ -7065,73 +7065,85 @@ static void intel_crtc_idle_timer(unsigned long arg)
        queue_work(dev_priv->wq, &dev_priv->idle_work);
 }
 
-static void intel_increase_pllclock(struct drm_crtc *crtc)
+static void __intel_crtc_increase_pllclock(struct intel_crtc *crtc)
 {
-       struct drm_device *dev = crtc->dev;
-       drm_i915_private_t *dev_priv = dev->dev_private;
-       struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-       int pipe = intel_crtc->pipe;
-       int dpll_reg = DPLL(pipe);
+       drm_i915_private_t *dev_priv = crtc->base.dev->dev_private;
+       int dpll_reg = DPLL(crtc->pipe);
        int dpll;
 
-       if (HAS_PCH_SPLIT(dev))
-               return;
-
-       if (!dev_priv->lvds_downclock_avail)
-               return;
-
        dpll = I915_READ(dpll_reg);
-       if (!HAS_PIPE_CXSR(dev) && (dpll & DISPLAY_RATE_SELECT_FPA1)) {
+       if (dpll & DISPLAY_RATE_SELECT_FPA1) {
                DRM_DEBUG_DRIVER("upclocking LVDS\n");
 
-               assert_panel_unlocked(dev_priv, pipe);
-
-               dpll &= ~DISPLAY_RATE_SELECT_FPA1;
-               I915_WRITE(dpll_reg, dpll);
-               intel_wait_for_vblank(dev, pipe);
-
-               dpll = I915_READ(dpll_reg);
-               if (dpll & DISPLAY_RATE_SELECT_FPA1)
-                       DRM_DEBUG_DRIVER("failed to upclock LVDS!\n");
+               assert_panel_unlocked(dev_priv, crtc->pipe);
+               I915_WRITE(dpll_reg, dpll & ~DISPLAY_RATE_SELECT_FPA1);
        }
 
        /* Schedule downclock */
-       mod_timer(&intel_crtc->idle_timer, jiffies +
-                 msecs_to_jiffies(CRTC_IDLE_TIMEOUT));
+       mod_timer(&crtc->idle_timer,
+                 jiffies + msecs_to_jiffies(CRTC_IDLE_TIMEOUT));
 }
 
-static void intel_decrease_pllclock(struct drm_crtc *crtc)
+static void intel_restore_pllclock(struct drm_crtc *crtc)
+{
+       struct drm_device *dev = crtc->dev;
+       drm_i915_private_t *dev_priv = dev->dev_private;
+       int reg;
+
+       if (HAS_PCH_SPLIT(dev) || HAS_PIPE_CXSR(dev))
+               return;
+
+       reg = DPLL(to_intel_crtc(crtc)->pipe);
+       I915_WRITE(reg, I915_READ(reg) & ~DISPLAY_RATE_SELECT_FPA1);
+}
+
+static void intel_increase_pllclock(struct drm_crtc *crtc)
 {
        struct drm_device *dev = crtc->dev;
        drm_i915_private_t *dev_priv = dev->dev_private;
        struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
-       int pipe = intel_crtc->pipe;
-       int dpll_reg = DPLL(pipe);
-       int dpll = I915_READ(dpll_reg);
 
-       if (HAS_PCH_SPLIT(dev))
+       if (HAS_PCH_SPLIT(dev) || HAS_PIPE_CXSR(dev))
                return;
 
        if (!dev_priv->lvds_downclock_avail)
                return;
 
+       if (intel_crtc_add_vblank_task(intel_crtc,
+                                      __intel_crtc_increase_pllclock))
+               __intel_crtc_increase_pllclock(intel_crtc);
+}
+
+static void __intel_crtc_decrease_pllclock(struct intel_crtc *crtc)
+{
+       drm_i915_private_t *dev_priv = crtc->base.dev->dev_private;
+       int dpll_reg = DPLL(crtc->pipe);
+
        /*
         * Since this is called by a timer, we should never get here in
         * the manual case.
         */
-       if (!HAS_PIPE_CXSR(dev) && intel_crtc->lowfreq_avail) {
-               DRM_DEBUG_DRIVER("downclocking LVDS\n");
+       DRM_DEBUG_DRIVER("downclocking LVDS\n");
 
-               assert_panel_unlocked(dev_priv, pipe);
+       assert_panel_unlocked(dev_priv, crtc->pipe);
+       I915_WRITE(dpll_reg, I915_READ(dpll_reg) | DISPLAY_RATE_SELECT_FPA1);
+}
 
-               dpll |= DISPLAY_RATE_SELECT_FPA1;
-               I915_WRITE(dpll_reg, dpll);
-               intel_wait_for_vblank(dev, pipe);
-               dpll = I915_READ(dpll_reg);
-               if (!(dpll & DISPLAY_RATE_SELECT_FPA1))
-                       DRM_DEBUG_DRIVER("failed to downclock LVDS!\n");
-       }
+static void intel_decrease_pllclock(struct drm_crtc *crtc)
+{
+       struct drm_device *dev = crtc->dev;
+       drm_i915_private_t *dev_priv = dev->dev_private;
+       struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+
+       if (HAS_PCH_SPLIT(dev) || HAS_PIPE_CXSR(dev))
+               return;
+
+       if (!dev_priv->lvds_downclock_avail || !intel_crtc->lowfreq_avail)
+               return;
 
+       if (intel_crtc_add_vblank_task(intel_crtc,
+                                      __intel_crtc_decrease_pllclock))
+               __intel_crtc_decrease_pllclock(intel_crtc);
 }
 
 /**
@@ -9234,7 +9246,6 @@ void intel_modeset_cleanup(struct drm_device *dev)
 {
        struct drm_i915_private *dev_priv = dev->dev_private;
        struct drm_crtc *crtc;
-       struct intel_crtc *intel_crtc;
 
        /* Clear the vblank worker prior to taking any locks */
        flush_scheduled_work();
@@ -9250,8 +9261,7 @@ void intel_modeset_cleanup(struct drm_device *dev)
                if (!crtc->fb)
                        continue;
 
-               intel_crtc = to_intel_crtc(crtc);
-               intel_increase_pllclock(crtc);
+               intel_restore_pllclock(crtc);
        }
 
        intel_disable_fbc(dev);
@@ -9276,10 +9286,8 @@ void intel_modeset_cleanup(struct drm_device *dev)
        flush_scheduled_work();
 
        /* Shut off idle work before the crtcs get freed. */
-       list_for_each_entry(crtc, &dev->mode_config.crtc_list, head) {
-               intel_crtc = to_intel_crtc(crtc);
-               del_timer_sync(&intel_crtc->idle_timer);
-       }
+       list_for_each_entry(crtc, &dev->mode_config.crtc_list, head)
+               del_timer_sync(&to_intel_crtc(crtc)->idle_timer);
        del_timer_sync(&dev_priv->idle_timer);
        cancel_work_sync(&dev_priv->idle_work);
 
-- 
1.7.9.1

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