[Intel-gfx] [PATCH] drm/i915: HDCP: retry link integrity check on failure

[Ramalingam C]

On 2020-05-04 at 14:35:24 +0200, Oliver Barta wrote:
> From: Oliver Barta <oliver.barta at aptiv.com>
> 
> A single Ri mismatch doesn't automatically mean that the link integrity
> is broken. Update and check of Ri and Ri' are done asynchronously. In
> case an update happens just between the read of Ri' and the check against
> Ri there will be a mismatch even if the link integrity is fine otherwise.

Thanks for working on this. Btw, did you face this sporadic link check
failure or theoretically you are fixing it?

IMO this change will rule out possible sporadic link check failures as
mentioned in the commit msg. Though I haven't faced this issue at my
testings.

Reviewed-by: Ramalingam C <ramalingam.c at intel.com>

> 
> Signed-off-by: Oliver Barta <oliver.barta at aptiv.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdmi.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_hdmi.c b/drivers/gpu/drm/i915/display/intel_hdmi.c
> index 010f37240710..3156fde392f2 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdmi.c
> @@ -1540,7 +1540,7 @@ int intel_hdmi_hdcp_toggle_signalling(struct intel_digital_port *intel_dig_port,
>  }
>  
>  static
> -bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
> +bool intel_hdmi_hdcp_check_link_once(struct intel_digital_port *intel_dig_port)
>  {
>  	struct drm_i915_private *i915 = to_i915(intel_dig_port->base.base.dev);
>  	struct intel_connector *connector =
> @@ -1563,8 +1563,7 @@ bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>  	if (wait_for((intel_de_read(i915, HDCP_STATUS(i915, cpu_transcoder, port)) &
>  		      (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC)) ==
>  		     (HDCP_STATUS_RI_MATCH | HDCP_STATUS_ENC), 1)) {
> -		drm_err(&i915->drm,
> -			"Ri' mismatch detected, link check failed (%x)\n",
> +		drm_dbg_kms(&i915->drm, "Ri' mismatch detected (%x)\n",
>  			intel_de_read(i915, HDCP_STATUS(i915, cpu_transcoder,
>  							port)));
>  		return false;
> @@ -1572,6 +1571,20 @@ bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>  	return true;
>  }
>  
> +static
> +bool intel_hdmi_hdcp_check_link(struct intel_digital_port *intel_dig_port)
> +{
> +	struct drm_i915_private *i915 = to_i915(intel_dig_port->base.base.dev);
> +	int retry;
> +
> +	for (retry = 0; retry < 3; retry++)
> +		if (intel_hdmi_hdcp_check_link_once(intel_dig_port))
> +			return true;
> +
> +	drm_err(&i915->drm, "Link check failed\n");
> +	return false;
> +}
> +
>  struct hdcp2_hdmi_msg_timeout {
>  	u8 msg_id;
>  	u16 timeout;
> -- 
> 2.20.1
>