Re: [PATCH v2 6/8] drm/i915: Detect panel's hdcp capability

[Sean Paul <seanpaul@chromium.org>]

On Sat, Feb 03, 2018 at 01:41:34AM +0530, Ramalingam C wrote:
> DP HDCP1.4 spec mandates that An can be written to panel only after
> detecting the panel's hdcp capability.
> 
> For DP 0th Bit of Bcaps register indicates the panel's hdcp capability
> For HDMI valid BKSV indicates the panel's hdcp capability.
> 
> For HDMI it is optional to detect the panel's hdcp capability before
> An Write.
> 
> v2:
>   Added comments explaining the need for action [Seanpaul].
>   Made panel's hdcp capability detection optional for hdmi [Seanpaul].
>   Defined a func for reading bcaps for DP [Seanpaul].
> 
> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c   | 39 +++++++++++++++++++++++++++++++++++----
>  drivers/gpu/drm/i915/intel_drv.h  |  4 ++++
>  drivers/gpu/drm/i915/intel_hdcp.c | 18 +++++++++++++++++-
>  drivers/gpu/drm/i915/intel_hdmi.c |  1 +
>  4 files changed, 57 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 03d86ff9b805..5fa6bb7dbb7a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5107,17 +5107,32 @@ static int intel_dp_hdcp_read_bstatus(struct intel_digital_port *intel_dig_port,
>  }
>  
>  static
> -int intel_dp_hdcp_repeater_present(struct intel_digital_port *intel_dig_port,
> -				   bool *repeater_present)
> +int intel_dp_hdcp_read_bcaps(struct intel_digital_port *intel_dig_port,
> +			     u8 *bcaps)
>  {
>  	ssize_t ret;
> -	u8 bcaps;
> +
>  	ret = drm_dp_dpcd_read(&intel_dig_port->dp.aux, DP_AUX_HDCP_BCAPS,
> -			       &bcaps, 1);
> +			       bcaps, 1);
>  	if (ret != 1) {
>  		DRM_ERROR("Read bcaps from DP/AUX failed (%zd)\n", ret);
>  		return ret >= 0 ? -EIO : ret;
>  	}
> +
> +	return 0;
> +}
> +
> +static
> +int intel_dp_hdcp_repeater_present(struct intel_digital_port *intel_dig_port,
> +				   bool *repeater_present)
> +{
> +	ssize_t ret;
> +	u8 bcaps;
> +
> +	ret = intel_dp_hdcp_read_bcaps(intel_dig_port, &bcaps);
> +	if (ret)
> +		return ret;
> +
>  	*repeater_present = bcaps & DP_BCAPS_REPEATER_PRESENT;
>  	return 0;
>  }
> @@ -5218,6 +5233,21 @@ bool intel_dp_hdcp_check_link(struct intel_digital_port *intel_dig_port)
>  	return !(bstatus & (DP_BSTATUS_LINK_FAILURE | DP_BSTATUS_REAUTH_REQ));
>  }
>  
> +static
> +int intel_dp_hdcp_capable(struct intel_digital_port *intel_dig_port,
> +			  bool *hdcp_capable)
> +{
> +	ssize_t ret;
> +	u8 bcaps;
> +
> +	ret = intel_dp_hdcp_read_bcaps(intel_dig_port, &bcaps);
> +	if (ret)
> +		return ret;
> +
> +	*hdcp_capable = bcaps & DP_BCAPS_HDCP_CAPABLE;
> +	return 0;
> +}
> +
>  static const struct intel_hdcp_shim intel_dp_hdcp_shim = {
>  	.write_an_aksv = intel_dp_hdcp_write_an_aksv,
>  	.read_bksv = intel_dp_hdcp_read_bksv,
> @@ -5229,6 +5259,7 @@ static const struct intel_hdcp_shim intel_dp_hdcp_shim = {
>  	.read_v_prime_part = intel_dp_hdcp_read_v_prime_part,
>  	.toggle_signalling = intel_dp_hdcp_toggle_signalling,
>  	.check_link = intel_dp_hdcp_check_link,
> +	.hdcp_capable = intel_dp_hdcp_capable,
>  };
>  
>  static void intel_edp_panel_vdd_sanitize(struct intel_dp *intel_dp)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index d6a808374dfb..468ec1e90e16 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -369,6 +369,10 @@ struct intel_hdcp_shim {
>  
>  	/* Ensures the link is still protected */
>  	bool (*check_link)(struct intel_digital_port *intel_dig_port);
> +
> +	/* Detects panel's hdcp capability. This is optional for HDMI. */
> +	int (*hdcp_capable)(struct intel_digital_port *intel_dig_port,
> +			    bool *hdcp_capable);
>  };
>  
>  struct intel_connector {
> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
> index 0cee79c86d7e..4b2821feb4b4 100644
> --- a/drivers/gpu/drm/i915/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
> @@ -414,12 +414,28 @@ static int intel_hdcp_auth(struct intel_digital_port *intel_dig_port,
>  		u32 reg;
>  		u8 shim[DRM_HDCP_RI_LEN];
>  	} ri;
> -	bool repeater_present;
> +	bool repeater_present, hdcp_capable;
>  
>  	dev_priv = intel_dig_port->base.base.dev->dev_private;
>  
>  	port = intel_dig_port->base.port;
>  
> +	/*
> +	 * Detects whether the display is HDCP capable. Although we check for
> +	 * valid Bksv below, the HDCP over DP spec requires that we check
> +	 * whether the display supports HDCP before we write An. For HDMI
> +	 * displays, this is not necessary.
> +	 */
> +	if (shim->hdcp_capable) {
> +		ret = shim->hdcp_capable(intel_dig_port, &hdcp_capable);
> +		if (ret)
> +			return ret;
> +		if (!hdcp_capable) {
> +			DRM_ERROR("Panel is not HDCP capable\n");
> +			return -EINVAL;
> +		}
> +	}
> +
>  	/* Initialize An with 2 random values and acquire it */
>  	for (i = 0; i < 2; i++)
>  		I915_WRITE(PORT_HDCP_ANINIT(port), get_random_u32());
> diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
> index f5d7bfb43006..1a05a4bf442e 100644
> --- a/drivers/gpu/drm/i915/intel_hdmi.c
> +++ b/drivers/gpu/drm/i915/intel_hdmi.c
> @@ -1117,6 +1117,7 @@ static const struct intel_hdcp_shim intel_hdmi_hdcp_shim = {
>  	.read_v_prime_part = intel_hdmi_hdcp_read_v_prime_part,
>  	.toggle_signalling = intel_hdmi_hdcp_toggle_signalling,
>  	.check_link = intel_hdmi_hdcp_check_link,
> +	.hdcp_capable = NULL,

nit: This isn't needed, it will already be initialized to NULL.

With that fixed:

Reviewed-by: Sean Paul <seanpaul@chromium.org>

>  };
>  
>  static void intel_hdmi_prepare(struct intel_encoder *encoder,
> -- 
> 2.7.4
> 

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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