drm/i915/hdcp: update cp_irq_count_cached in intel_dp_hdcp2_read_msg()

Update cp_irq_count_cached when reading messages rather than when
writing a message to make sure the value is up to date and not
stale from a previously handled CP_IRQ.

AKE flow  doesn't always respond to a read with a ACK write msg.
E.g. AKE_Send_Pairing_Info will "timeout" because we received
a CP_IRQ for reading AKE_Send_H_Prime but no write occurred between that
and reading AKE_Send_Pairing_Info so cp_irq_count_cached is stale
causing the wait to return right away rather than waiting for a new
CP_IRQ.

Signed-off-by: Juston Li <juston.li@intel.com>
Acked-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
Tested-by: Suraj K <suraj.kandpal@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210819184835.1181323-2-juston.li@intel.com

drivers/gpu/drm/i915/display/intel_dp_hdcp.c

@@ -446,8 +446,6 @@ static
 int intel_dp_hdcp2_write_msg(struct intel_digital_port *dig_port,
 			     void *buf, size_t size)
 {
-	struct intel_dp *dp = &dig_port->dp;
-	struct intel_hdcp *hdcp = &dp->attached_connector->hdcp;
 	unsigned int offset;
 	u8 *byte = buf;
 	ssize_t ret, bytes_to_write, len;
@@ -463,8 +461,6 @@ int intel_dp_hdcp2_write_msg(struct intel_digital_port *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;
@@ -530,6 +526,8 @@ int intel_dp_hdcp2_read_msg(struct intel_digital_port *dig_port,
 			    u8 msg_id, void *buf, size_t size)
 {
 	struct drm_i915_private *i915 = to_i915(dig_port->base.base.dev);
+	struct intel_dp *dp = &dig_port->dp;
+	struct intel_hdcp *hdcp = &dp->attached_connector->hdcp;
 	unsigned int offset;
 	u8 *byte = buf;
 	ssize_t ret, bytes_to_recv, len;
@@ -546,6 +544,8 @@ int intel_dp_hdcp2_read_msg(struct intel_digital_port *dig_port,
 	if (ret < 0)
 		return ret;
 
+	hdcp->cp_irq_count_cached = atomic_read(&hdcp->cp_irq_count);
+
 	if (msg_id == HDCP_2_2_REP_SEND_RECVID_LIST) {
 		ret = get_receiver_id_list_size(dig_port);
 		if (ret < 0)