[PATCH 4/8] drm/i915: avoid waking up from PC8 on DP AUX operations

[Paulo Zanoni <przanoni@gmail.com>]

From: Paulo Zanoni <paulo.r.zanoni@intel.com>

If we're already allowing PC8, just don't use the IRQs, so we won't
need to wake from PC8. Waking up from PC8 is a slow thing, so avoid it
when we can.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
 drivers/gpu/drm/i915/intel_dp.c | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
index a531912..88ccbd5 100644
--- a/drivers/gpu/drm/i915/intel_dp.c
+++ b/drivers/gpu/drm/i915/intel_dp.c
@@ -315,6 +315,24 @@ static uint32_t get_aux_clock_divider(struct intel_dp *intel_dp,
 	}
 }
 
+static bool intel_dp_use_aux_irq(struct drm_device *dev)
+{
+	struct drm_i915_private *dev_priv = dev->dev_private;
+	bool ret;
+
+	if (INTEL_INFO(dev)->gen <= 4 || IS_VALLEYVIEW(dev))
+		return false;
+
+	/* In case we're already allowing PC8, just don't use IRQs, so we won't
+	 * need to call intel_aux_display_runtime_get and then we won't wake up
+	 * from PC8. */
+	mutex_lock(&dev_priv->pc8.lock);
+	ret = (dev_priv->pc8.forbid_refcnt != 0);
+	mutex_unlock(&dev_priv->pc8.lock);
+
+	return ret;
+}
+
 static int
 intel_dp_aux_ch(struct intel_dp *intel_dp,
 		uint8_t *send, int send_bytes,
@@ -329,7 +347,7 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
 	int i, ret, recv_bytes;
 	uint32_t status;
 	int try, precharge, clock = 0;
-	bool has_aux_irq = INTEL_INFO(dev)->gen >= 5 && !IS_VALLEYVIEW(dev);
+	bool has_aux_irq = intel_dp_use_aux_irq(dev);
 
 	/* dp aux is extremely sensitive to irq latency, hence request the
 	 * lowest possible wakeup latency and so prevent the cpu from going into
@@ -344,7 +362,8 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
 	else
 		precharge = 5;
 
-	intel_aux_display_runtime_get(dev_priv);
+	if (has_aux_irq)
+		intel_aux_display_runtime_get(dev_priv);
 
 	/* Try to wait for any previous AUX channel activity */
 	for (try = 0; try < 3; try++) {
@@ -436,7 +455,8 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
 	ret = recv_bytes;
 out:
 	pm_qos_update_request(&dev_priv->pm_qos, PM_QOS_DEFAULT_VALUE);
-	intel_aux_display_runtime_put(dev_priv);
+	if (has_aux_irq)
+		intel_aux_display_runtime_put(dev_priv);
 
 	return ret;
 }
-- 
1.8.1.2