[Intel-gfx] [PATCH 2/3] drm/i915/hdcp: read RxInfo once when reading RepeaterAuth_Send_ReceiverID_List

[Juston Li]

When reading RepeaterAuth_Send_ReceiverID_List, RxInfo is read by itself
once to retrieve the DEVICE_COUNT to calculate the size of the
ReceiverID list then read a second time as a part of reading ReceiverID
list.

On some MST docking stations, RxInfo can only be read after the RxStatus
READY bit is set otherwise the read will return -EIO. The spec states that
the READY bit should be cleared as soon as RxInfo has been read.

In this case, the first RxInfo read succeeds but after the READY bit is
cleared, the second read fails.

Fix it by reading RxInfo once and storing it before reading the rest of
RepeaterAuth_Send_ReceiverID_List once we know the size.

Modify get_receiver_id_list_size() to read and store RxInfo in the
message buffer and also parse DEVICE_COUNT so we know the size of
RepeaterAuth_Send_ReceiverID_List.

Afterwards, retrieve the rest of the message at the offset for
seq_num_V.

Changes in v4:
- rebase and edit commit message

Changes in v3:
- remove comment

Changes in v2:
- remove unnecessary moving of drm_i915_private from patch 1

Signed-off-by: Juston Li <juston.li at intel.com>
Acked-by: Anshuman Gupta <anshuman.gupta at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 30 ++++++++++----------
 include/drm/drm_dp_helper.h                  |  2 +-
 2 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
index 1d0096654776..526fd58b9b51 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
@@ -496,11 +496,10 @@ get_rxinfo_hdcp_1_dev_downstream(struct intel_digital_port *dig_port, bool *hdcp
 }
 
 static
-ssize_t get_receiver_id_list_size(struct intel_digital_port *dig_port)
+ssize_t get_receiver_id_list_rx_info(struct intel_digital_port *dig_port, u32 *dev_cnt, u8 *byte)
 {
-	u8 rx_info[HDCP_2_2_RXINFO_LEN];
-	u32 dev_cnt;
 	ssize_t ret;
+	u8 *rx_info = byte;
 
 	ret = drm_dp_dpcd_read(&dig_port->dp.aux,
 			       DP_HDCP_2_2_REG_RXINFO_OFFSET,
@@ -508,15 +507,11 @@ ssize_t get_receiver_id_list_size(struct intel_digital_port *dig_port)
 	if (ret != HDCP_2_2_RXINFO_LEN)
 		return ret >= 0 ? -EIO : ret;
 
-	dev_cnt = (HDCP_2_2_DEV_COUNT_HI(rx_info[0]) << 4 |
+	*dev_cnt = (HDCP_2_2_DEV_COUNT_HI(rx_info[0]) << 4 |
 		   HDCP_2_2_DEV_COUNT_LO(rx_info[1]));
 
-	if (dev_cnt > HDCP_2_2_MAX_DEVICE_COUNT)
-		dev_cnt = HDCP_2_2_MAX_DEVICE_COUNT;
-
-	ret = sizeof(struct hdcp2_rep_send_receiverid_list) -
-		HDCP_2_2_RECEIVER_IDS_MAX_LEN +
-		(dev_cnt * HDCP_2_2_RECEIVER_ID_LEN);
+	if (*dev_cnt > HDCP_2_2_MAX_DEVICE_COUNT)
+		*dev_cnt = HDCP_2_2_MAX_DEVICE_COUNT;
 
 	return ret;
 }
@@ -534,6 +529,7 @@ int intel_dp_hdcp2_read_msg(struct intel_digital_port *dig_port,
 	const struct hdcp2_dp_msg_data *hdcp2_msg_data;
 	ktime_t msg_end = ktime_set(0, 0);
 	bool msg_expired;
+	u32 dev_cnt;
 
 	hdcp2_msg_data = get_hdcp2_dp_msg_data(msg_id);
 	if (!hdcp2_msg_data)
@@ -546,17 +542,21 @@ int intel_dp_hdcp2_read_msg(struct intel_digital_port *dig_port,
 
 	hdcp->cp_irq_count_cached = atomic_read(&hdcp->cp_irq_count);
 
+	/* DP adaptation msgs has no msg_id */
+	byte++;
+
 	if (msg_id == HDCP_2_2_REP_SEND_RECVID_LIST) {
-		ret = get_receiver_id_list_size(dig_port);
+		ret = get_receiver_id_list_rx_info(dig_port, &dev_cnt, byte);
 		if (ret < 0)
 			return ret;
 
-		size = ret;
+		byte += ret;
+		size = sizeof(struct hdcp2_rep_send_receiverid_list) -
+		HDCP_2_2_RXINFO_LEN - HDCP_2_2_RECEIVER_IDS_MAX_LEN +
+		(dev_cnt * HDCP_2_2_RECEIVER_ID_LEN);
 	}
-	bytes_to_recv = size - 1;
 
-	/* DP adaptation msgs has no msg_id */
-	byte++;
+	bytes_to_recv = size - 1;
 
 	while (bytes_to_recv) {
 		len = bytes_to_recv > DP_AUX_MAX_PAYLOAD_BYTES ?
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 3f2715eb965f..7476e7c6d0be 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1413,7 +1413,7 @@ enum drm_dp_phy {
 #define DP_HDCP_2_2_LC_INIT_OFFSET		DP_HDCP_2_2_REG_RN_OFFSET
 #define DP_HDCP_2_2_LC_SEND_LPRIME_OFFSET	DP_HDCP_2_2_REG_LPRIME_OFFSET
 #define DP_HDCP_2_2_SKE_SEND_EKS_OFFSET		DP_HDCP_2_2_REG_EDKEY_KS_OFFSET
-#define DP_HDCP_2_2_REP_SEND_RECVID_LIST_OFFSET	DP_HDCP_2_2_REG_RXINFO_OFFSET
+#define DP_HDCP_2_2_REP_SEND_RECVID_LIST_OFFSET	DP_HDCP_2_2_REG_SEQ_NUM_V_OFFSET
 #define DP_HDCP_2_2_REP_SEND_ACK_OFFSET		DP_HDCP_2_2_REG_V_OFFSET
 #define DP_HDCP_2_2_REP_STREAM_MANAGE_OFFSET	DP_HDCP_2_2_REG_SEQ_NUM_M_OFFSET
 #define DP_HDCP_2_2_REP_STREAM_READY_OFFSET	DP_HDCP_2_2_REG_MPRIME_OFFSET
-- 
2.31.1