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

[Sean Paul <sean@poorly.run>]

On Mon, May 4, 2020 at 1:32 PM Oliver Barta <o.barta89@gmail.com> wrote:
>
> From: Oliver Barta <oliver.barta@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.
>
> Signed-off-by: Oliver Barta <oliver.barta@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)) {

Why doesn't the wait_for catch this?

Sean

> -               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
>
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