Re: [Intel-gfx] [PATCH v6 2/3] drm/i915/hdcp: read RxInfo once when reading RepeaterAuth_Send_ReceiverID_List

["Gupta, Anshuman" <anshuman.gupta@intel.com>]

> -----Original Message-----
> From: Li, Juston <juston.li@intel.com>
> Sent: Friday, August 20, 2021 12:19 AM
> To: intel-gfx@lists.freedesktop.org
> Cc: seanpaul@chromium.org; Gupta, Anshuman <anshuman.gupta@intel.com>;
> C, Ramalingam <ramalingam.c@intel.com>; Vivi, Rodrigo
> <rodrigo.vivi@intel.com>; Li, Juston <juston.li@intel.com>
> Subject: [Intel-gfx] [PATCH v6 2/3] drm/i915/hdcp: read RxInfo once when
> reading RepeaterAuth_Send_ReceiverID_List
> 
> 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 v5:
> - Don't change the offset define for Send_ReceiverID_List
>   When reading, update message offset to account for RxInfo being read
> 
> 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@intel.com>
> Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
> Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Adding Suraj to this thread.
> ---
>  drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 31 ++++++++++----------
>  1 file changed, 16 insertions(+), 15 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..fbfb3c4d16bb 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 +542,22 @@ 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);
> +		offset += HDCP_2_2_RXINFO_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 ?
> --
> 2.31.1