[Intel-gfx] [PATCH 5/7] drm/i915/dp: Add methods to update link train params

[Ander Conselvan De Oliveira]

On Fri, 2015-12-11 at 15:09 +0530, Durgadoss R wrote:
> Retrying with reduced lanes/bw and updating the final
> available lanes/bw to DPCD is needed for upfront link
> train logic. Hence, this patch adds these methods
> and exports them so that these can be called from
> other files like ddi.c/display.c.
> 
> Signed-off-by: Durgadoss R <durgadoss.r at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c  | 34 ++++++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index f335c92..d8f7830 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -1660,6 +1660,40 @@ void intel_dp_set_link_params(struct intel_dp
> *intel_dp,
>  	intel_dp->lane_count = pipe_config->lane_count;
>  }
>  
> +void intel_dp_update_dpcd_params(struct intel_dp *intel_dp)
> +{
> +	intel_dp->dpcd[DP_MAX_LANE_COUNT] &= ~DP_MAX_LANE_COUNT_MASK;
> +	intel_dp->dpcd[DP_MAX_LANE_COUNT] |=
> +			intel_dp->lane_count & DP_MAX_LANE_COUNT_MASK;
> +
> +	intel_dp->dpcd[DP_MAX_LINK_RATE] =
> +			drm_dp_link_rate_to_bw_code(intel_dp->link_rate);
> +}
> +
> +bool intel_dp_get_link_retry_params(uint8_t *lane_count, uint8_t *link_bw)
> +{
> +	/*
> +	 * As per DP1.3 Spec, retry all link rates for a particular
> +	 * lane count value, before reducing number of lanes.
> +	 */
> +	if (*link_bw == DP_LINK_BW_5_4) {
> +		*link_bw = DP_LINK_BW_2_7;
> +	} else if (*link_bw == DP_LINK_BW_2_7) {
> +		*link_bw = DP_LINK_BW_1_62;
> +	} else if (*lane_count == 4) {
> +		*lane_count = 2;
> +		*link_bw = DP_LINK_BW_5_4;
> +	} else if (*lane_count == 2) {
> +		*lane_count = 1;
> +		*link_bw = DP_LINK_BW_5_4;

If the sink doesn't support 5.4 Gbps, shouldn't we skip that rate?

Also, it would be easier to review these functions if they were in same patch
were they are used.

Ander

> +	} else {
> +		/* Tried all combinations, so exit */
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
>  static void intel_dp_prepare(struct intel_encoder *encoder)
>  {
>  	struct drm_device *dev = encoder->base.dev;
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index faa91fc..5cefb0e 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1233,6 +1233,8 @@ bool intel_dp_init_connector(struct intel_digital_port
> *intel_dig_port,
>  			     struct intel_connector *intel_connector);
>  void intel_dp_set_link_params(struct intel_dp *intel_dp,
>  			      const struct intel_crtc_state *pipe_config);
> +void intel_dp_update_dpcd_params(struct intel_dp *intel_dp);
> +bool intel_dp_get_link_retry_params(uint8_t *lane_count, uint8_t *link_bw);
>  void intel_dp_start_link_train(struct intel_dp *intel_dp);
>  void intel_dp_stop_link_train(struct intel_dp *intel_dp);
>  void intel_dp_sink_dpms(struct intel_dp *intel_dp, int mode);