Re: [PATCH] drm/i915/hdcp: Handle HDCP Line Rekeying for HDCP 1.4

[Jani Nikula <jani.nikula@intel.com>]

On Wed, 06 Nov 2024, Suraj Kandpal <suraj.kandpal@intel.com> wrote:
> TRANS_DDI_FUNC_CTL asks us to disable hdcp line rekeying when not in
> hdcp 2.2 and we are not using an hdmi transcoder and it need to be
> enabled when we are using an HDMI transcoder to enable HDCP 1.4.
> We use intel_de_rmw cycles to update TRANS_DDI_FUNC_CTL register so
> we cannot depend on the value being 0 by default everytime which calls
> for seprate handling of HDCP 1.4 case.
>
> --v2
> -Use the exising function and modify it based on a bool rather than
> have a different function [Matt]
>
> --v3
> -No need for kzalloc [Jani]

The code still needs to make sense! You can't just remove allocation and
use whatever stack garbage rekey_reg happens to point at. Look at all
the other code that uses i915_reg_t. You can't possibly assume I
would've needed to say "it shouldn't be a pointer at all"?

BR,
Jani.

>
> Bspec: 69964, 50493, 50054
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_hdcp.c | 36 +++++++++++++----------
>  1 file changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_hdcp.c b/drivers/gpu/drm/i915/display/intel_hdcp.c
> index 4e937fbba4d2..6ad5efc9711c 100644
> --- a/drivers/gpu/drm/i915/display/intel_hdcp.c
> +++ b/drivers/gpu/drm/i915/display/intel_hdcp.c
> @@ -32,27 +32,31 @@
>  #define HDCP2_LC_RETRY_CNT			3
>  
>  static void
> -intel_hdcp_disable_hdcp_line_rekeying(struct intel_encoder *encoder,
> -				      struct intel_hdcp *hdcp)
> +intel_hdcp_adjust_hdcp_line_rekeying(struct intel_encoder *encoder,
> +				     struct intel_hdcp *hdcp,
> +				     bool enable)
>  {
>  	struct intel_display *display = to_intel_display(encoder);
> +	i915_reg_t *rekey_reg;
> +	u32 rekey_bit;
>  
>  	/* Here we assume HDMI is in TMDS mode of operation */
>  	if (encoder->type != INTEL_OUTPUT_HDMI)
>  		return;
>  
> -	if (DISPLAY_VER(display) >= 30)
> -		intel_de_rmw(display,
> -			     TRANS_DDI_FUNC_CTL(display, hdcp->cpu_transcoder),
> -			     0, XE3_TRANS_DDI_HDCP_LINE_REKEY_DISABLE);
> -	else if (IS_DISPLAY_VERx100_STEP(display, 1401, STEP_B0, STEP_FOREVER) ||
> -		 IS_DISPLAY_VERx100_STEP(display, 2000, STEP_B0, STEP_FOREVER))
> -		intel_de_rmw(display,
> -			     TRANS_DDI_FUNC_CTL(display, hdcp->cpu_transcoder),
> -			     0, TRANS_DDI_HDCP_LINE_REKEY_DISABLE);
> -	else if (IS_DISPLAY_VERx100_STEP(display, 1400, STEP_D0, STEP_FOREVER))
> -		intel_de_rmw(display, MTL_CHICKEN_TRANS(hdcp->cpu_transcoder),
> -			     0, HDCP_LINE_REKEY_DISABLE);
> +	if (DISPLAY_VER(display) >= 30) {
> +		*rekey_reg = TRANS_DDI_FUNC_CTL(display, hdcp->cpu_transcoder);
> +		rekey_bit = XE3_TRANS_DDI_HDCP_LINE_REKEY_DISABLE;
> +	} else if (IS_DISPLAY_VERx100_STEP(display, 1401, STEP_B0, STEP_FOREVER) ||
> +		   IS_DISPLAY_VERx100_STEP(display, 2000, STEP_B0, STEP_FOREVER)) {
> +		*rekey_reg = TRANS_DDI_FUNC_CTL(display, hdcp->cpu_transcoder);
> +		rekey_bit = TRANS_DDI_HDCP_LINE_REKEY_DISABLE;
> +	} else if (IS_DISPLAY_VERx100_STEP(display, 1400, STEP_D0, STEP_FOREVER)) {
> +		*rekey_reg = MTL_CHICKEN_TRANS(hdcp->cpu_transcoder);
> +		rekey_bit = HDCP_LINE_REKEY_DISABLE;
> +	}
> +
> +	intel_de_rmw(display, *rekey_reg, rekey_bit, enable ? 0 : rekey_bit);
>  }
>  
>  static int intel_conn_to_vcpi(struct intel_atomic_state *state,
> @@ -1049,6 +1053,8 @@ static int intel_hdcp1_enable(struct intel_connector *connector)
>  		return ret;
>  	}
>  
> +	intel_hdcp_adjust_hdcp_line_rekeying(connector->encoder, hdcp, true);
> +
>  	/* Incase of authentication failures, HDCP spec expects reauth. */
>  	for (i = 0; i < tries; i++) {
>  		ret = intel_hdcp_auth(connector);
> @@ -2062,7 +2068,7 @@ static int _intel_hdcp2_enable(struct intel_atomic_state *state,
>  		    connector->base.base.id, connector->base.name,
>  		    hdcp->content_type);
>  
> -	intel_hdcp_disable_hdcp_line_rekeying(connector->encoder, hdcp);
> +	intel_hdcp_adjust_hdcp_line_rekeying(connector->encoder, hdcp, false);
>  
>  	ret = hdcp2_authenticate_and_encrypt(state, connector);
>  	if (ret) {

-- 
Jani Nikula, Intel