drm/i915: CP_IRQ handling for DP HDCP2.2 msgs

Implements the
	Waitqueue is created to wait for CP_IRQ
	Signaling the CP_IRQ arrival through atomic variable.
	For applicable DP HDCP2.2 msgs read wait for CP_IRQ.

As per HDCP2.2 spec "HDCP Transmitters must process CP_IRQ interrupts
when they are received from HDCP Receivers"

Without CP_IRQ processing, DP HDCP2.2 H_Prime msg was getting corrupted
while reading it based on corresponding status bit. This creates the
random failures in reading the DP HDCP2.2 msgs.

v2:
  CP_IRQ arrival is tracked based on the atomic val inc [daniel]
  Recording the reviewed-by Daniel from IRC.
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/1550338640-17470-16-git-send-email-ramalingam.c@intel.com

drivers/gpu/drm/i915/intel_dp.c

@@ -5623,6 +5623,18 @@ void intel_dp_encoder_suspend(struct intel_encoder *intel_encoder)
 		edp_panel_vdd_off_sync(intel_dp);
 }
 
+static void intel_dp_hdcp_wait_for_cp_irq(struct intel_hdcp *hdcp, int timeout)
+{
+	long ret;
+
+#define C (hdcp->cp_irq_count_cached != atomic_read(&hdcp->cp_irq_count))
+	ret = wait_event_interruptible_timeout(hdcp->cp_irq_queue, C,
+					       msecs_to_jiffies(timeout));
+
+	if (!ret)
+		DRM_DEBUG_KMS("Timedout at waiting for CP_IRQ\n");
+}
+
 static
 int intel_dp_hdcp_write_an_aksv(struct intel_digital_port *intel_dig_port,
 				u8 *an)
@@ -5967,14 +5979,13 @@ intel_dp_hdcp2_wait_for_msg(struct intel_digital_port *intel_dig_port,
 		mdelay(timeout);
 		ret = 0;
 	} else {
-		/* TODO: In case if you need to wait on CP_IRQ, do it here */
-		ret = __wait_for(ret =
-				 hdcp2_detect_msg_availability(intel_dig_port,
-							       msg_id,
-							       &msg_ready),
-				 !ret && msg_ready, timeout * 1000,
-				 1000, 5 * 1000);
-
+		/*
+		 * As we want to check the msg availability at timeout, Ignoring
+		 * the timeout at wait for CP_IRQ.
+		 */
+		intel_dp_hdcp_wait_for_cp_irq(hdcp, timeout);
+		ret = hdcp2_detect_msg_availability(intel_dig_port,
+						    msg_id, &msg_ready);
 		if (!msg_ready)
 			ret = -ETIMEDOUT;
 	}
@@ -6001,6 +6012,8 @@ static
 int intel_dp_hdcp2_write_msg(struct intel_digital_port *intel_dig_port,
 			     void *buf, size_t size)
 {
+	struct intel_dp *dp = &intel_dig_port->dp;
+	struct intel_hdcp *hdcp = &dp->attached_connector->hdcp;
 	unsigned int offset;
 	u8 *byte = buf;
 	ssize_t ret, bytes_to_write, len;
@@ -6016,6 +6029,8 @@ int intel_dp_hdcp2_write_msg(struct intel_digital_port *intel_dig_port,
 	bytes_to_write = size - 1;
 	byte++;
 
+	hdcp->cp_irq_count_cached = atomic_read(&hdcp->cp_irq_count);
+
 	while (bytes_to_write) {
 		len = bytes_to_write > DP_AUX_MAX_PAYLOAD_BYTES ?
 				DP_AUX_MAX_PAYLOAD_BYTES : bytes_to_write;

drivers/gpu/drm/i915/intel_drv.h

@@ -474,6 +474,14 @@ struct intel_hdcp {
 	 * over re-Auth has to be triggered.
 	 */
 	u32 seq_num_m;
+
+	/*
+	 * Work queue to signal the CP_IRQ. Used for the waiters to read the
+	 * available information from HDCP DP sink.
+	 */
+	wait_queue_head_t cp_irq_queue;
+	atomic_t cp_irq_count;
+	int cp_irq_count_cached;
 };
 
 struct intel_connector {

drivers/gpu/drm/i915/intel_hdcp.c

@@ -1806,6 +1806,7 @@ int intel_hdcp_init(struct intel_connector *connector,
 
 	if (is_hdcp2_supported(dev_priv))
 		intel_hdcp2_init(connector);
+	init_waitqueue_head(&hdcp->cp_irq_queue);
 
 	return 0;
 }
@@ -1935,12 +1936,8 @@ void intel_hdcp_handle_cp_irq(struct intel_connector *connector)
 	if (!hdcp->shim)
 		return;
 
-	/*
-	 * CP_IRQ could be triggered due to 1. HDCP2.2 auth msgs availability,
-	 * 2. link failure and 3. repeater reauth request. At present we dont
-	 * handle the CP_IRQ for the HDCP2.2 auth msg availability for read.
-	 * To handle other two causes for CP_IRQ we have the work_fn which is
-	 * scheduled here.
-	 */
+	atomic_inc(&connector->hdcp.cp_irq_count);
+	wake_up_all(&connector->hdcp.cp_irq_queue);
+
 	schedule_delayed_work(&hdcp->check_work, 0);
 }