Re: [PATCH 2/3] drm/i915: Displayport compliance test 4.2.2.7 support

[Daniel Vetter <daniel@ffwll.ch>]

On Tue, Jun 09, 2015 at 05:22:19PM -0700, Todd Previte wrote:
> Adds support for complying with the requirements for test 4.2.2.7 Branch
> Device Detection upon HPD Plug Event in the Displayport Link CTS 1.2 Core
> rev1.1. This test checks to see if the source device can properly detect
> a downstream branch device connected to the attached sink. It does so by
> advertising the presence of a downstream port through the DPCD. The sink
> count and content protection readiness bits are saved in the intel_dp
> struct.
> 
> Note that as of HDCP 1.3 Displayport amendment, the CP_READY bit (bit 6)
> in the SINK_COUNT register (DPCD 0x200) is no longer used. This bit
> is stored here for compatibility for pre-HDCP 1.3 devices.
> 
> V1:
> - Fixed formatting errors
> V2:
> - Updated for versioning
> 
> Signed-off-by: Todd Previte <tprevite@gmail.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 12 +++++++++++-
>  drivers/gpu/drm/i915/intel_drv.h |  4 ++++
>  2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 14147d0..697857a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3856,8 +3856,18 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
>  	intel_dp_print_rates(intel_dp);
>  
>  	if (!(intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] &
> -	      DP_DWN_STRM_PORT_PRESENT))
> +	      DP_DWN_STRM_PORT_PRESENT)) {
>  		return true; /* native DP sink */
> +	} else {
> +		uint8_t dpcd_byte;
> +		/* Read Sink Count - DP Link CTS 1.2a rev1.1 4.2.2.7 */
> +		intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
> +					&dpcd_byte, 1);
> +		intel_dp->sink_count = DP_GET_SINK_COUNT(dpcd_byte);
> +		intel_dp->cp_ready = (dpcd_byte & DP_SINK_CP_READY) >> 6;
> +		DRM_DEBUG_KMS("Sink count: %d  CP: %02x\n",
> +			      intel_dp->sink_count, intel_dp->cp_ready);
> +	}
>  
>  	if (intel_dp->dpcd[DP_DPCD_REV] == 0x10)
>  		return true; /* no per-port downstream info */
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 6c71be9..f9a935c 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -744,6 +744,10 @@ struct intel_dp {
>  	unsigned long compliance_test_type;
>  	unsigned long compliance_test_data;
>  	bool compliance_test_active;
> +
> +	/* Branch device support */
> +	uint8_t sink_count;
> +	uint8_t cp_ready;

Isn't this something that the dp helpers already maintain? If so then we
should probably use that one. If not I wonder whether we shouldn't do
something with these sink values instead of just passing them around ...
-Daniel

>  };
>  
>  struct intel_digital_port {
> -- 
> 1.9.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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