[Intel-gfx] [PATCH] drm/dp: implement EXTENDED_RECEIVER_CAPABILITY_FIELD_PRESENT

[Manasi Navare]

What is the status of this patch?
I am hitting this issue with one of the DP 1.4 sinks where the correct
values of DPCD are present at this new offset of 0x2200 else I see
bad values for REV and Max_link_rate etc..
So we absolutely need this for DP 1.4 sinks.

Manasi

On Wed, May 16, 2018 at 09:33:42AM -0700, matthew.s.atwood at intel.com wrote:
> From: Matt Atwood <matthew.s.atwood at intel.com>
> 
> According to DP spec (2.9.3.1 of DP 1.4) if
> EXTENDED_RECEIVER_CAPABILITY_FIELD_PRESENT is set the addresses in DPCD
> 02200h through 0220Fh shall contain the DPRX's true capability. These
> values will match 00000h through 0000Fh, except for DPCD_REV,
> MAX_LINK_RATE, DOWN_STREAM_PORT_PRESENT.
> 
> Read from DPCD once for all 3 values as this is an expensive operation.
> Spec mentions that all of address space 02200h through 0220Fh should
> contain the right information however currently only 3 values can
> differ.
> 
> There is no address space in the intel_dp->dpcd struct for addresses
> 02200h through 0220Fh, and since so much of the data is a identical,
> simply overwrite the values stored in 00000h through 0000Fh with the
> values that can be overwritten from addresses 02200h through 0220Fh
> 
> Signed-off-by: Matt Atwood <matthew.s.atwood at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 14 ++++++++++++++
>  include/drm/drm_dp_helper.h     |  5 +++--
>  2 files changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index dde92e4af5d3..899ebc5cece6 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3738,6 +3738,20 @@ intel_dp_read_dpcd(struct intel_dp *intel_dp)
>  			     sizeof(intel_dp->dpcd)) < 0)
>  		return false; /* aux transfer failed */
>  
> +	if (intel_dp->dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
> +	    DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT &&
> +	    intel_dp->dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14) {
> +		uint8_t dpcd_ext[16];
> +
> +		if (drm_dp_dpcd_read(&intel_dp->aux, DP_DP13_DPCD_REV,
> +		    &dpcd_ext, sizeof(dpcd_ext)) < 0)
> +			return false; /* aux transfer failed */
> +
> +		intel_dp->dpcd[DP_DPCD_REV] = dpcd_ext[DP_DPCD_REV];
> +		intel_dp->dpcd[DP_MAX_LINK_RATE] = dpcd_ext[DP_MAX_LINK_RATE];
> +		intel_dp->dpcd[DP_DOWNSTREAMPORT_PRESENT] =
> +			dpcd_ext[DP_DOWNSTREAMPORT_PRESENT];
> +	}
>  	DRM_DEBUG_KMS("DPCD: %*ph\n", (int) sizeof(intel_dp->dpcd), intel_dp->dpcd);
>  
>  	return intel_dp->dpcd[DP_DPCD_REV] != 0;
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index c01564991a9f..757bd5913f3d 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -123,8 +123,9 @@
>  # define DP_FRAMING_CHANGE_CAP		    (1 << 1)
>  # define DP_DPCD_DISPLAY_CONTROL_CAPABLE     (1 << 3) /* edp v1.2 or higher */
>  
> -#define DP_TRAINING_AUX_RD_INTERVAL         0x00e   /* XXX 1.2? */
> -# define DP_TRAINING_AUX_RD_MASK            0x7F    /* XXX 1.2? */
> +#define DP_TRAINING_AUX_RD_INTERVAL             0x00e   /* XXX 1.2? */
> +# define DP_TRAINING_AUX_RD_MASK                0x7F    /* XXX 1.2? */
> +# define DP_EXTENDED_RECEIVER_CAP_FIELD_PRESENT (1 << 7)/* XXX 1.2? */
>  
>  #define DP_ADAPTER_CAP			    0x00f   /* 1.2 */
>  # define DP_FORCE_LOAD_SENSE_CAP	    (1 << 0)
> -- 
> 2.17.0
> 
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