Re: [Intel-gfx] [PATCH v3 1/3] drm/i915/hdcp: update cp_irq_count_cached in intel_dp_hdcp2_read_msg()

[Ramalingam C <ramalingam.c@intel.com>]

On 2021-08-10 at 16:52:10 -0700, Juston Li wrote:
> 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.

LGTM.

Reviewed-by: Ramalingam C <ramalingam.c@intel.com>
> 
> Signed-off-by: Juston Li <juston.li@intel.com>
> Acked-by: Anshuman Gupta <anshuman.gupta@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_dp_hdcp.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c b/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> index d697d169e8c1..1d0096654776 100644
> --- a/drivers/gpu/drm/i915/display/intel_dp_hdcp.c
> +++ b/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)
> -- 
> 2.31.1
>