Re: [v4 6/7] i915/dp/fec: Configure the Forward Error Correction bits.

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Oct 30, 2018 at 05:45:16PM -0700, Anusha Srivatsa wrote:
> If FEC is supported, the corresponding
> DP_TP_CTL register bits have to be configured.
> 
> The driver has to program the FEC_ENABLE in DP_TP_CTL[30] register
> and wait till FEC_STATUS in DP_TP_CTL[28] is 1.
> Also add the warn message to make sure that the control
> register is already active while enabling FEC.
> 
> v2:
> - Change commit message. Configure fec state after
>   link training (Manasi, Gaurav)
> - Remove redundent checks (Manasi)
> - Remove the registers that get added automagically (Anusha)
> 
> v3: s/intel_dp_set_fec_state()/intel_dp_enable_fec_state() (Gaurav)
> 
> v4: rebased.
> 
> v5:
> - Move the code to the proper spot, according to spec.(Ville)
> - Use fec state as a check too.
> 
> Cc: Gaurav K Singh <gaurav.k.singh@intel.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Signed-off-by: Anusha Srivatsa <anusha.srivatsa@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_reg.h  |  2 ++
>  drivers/gpu/drm/i915/intel_ddi.c | 30 ++++++++++++++++++++++++++++++
>  drivers/gpu/drm/i915/intel_drv.h |  2 ++
>  3 files changed, 34 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index e85f53cb9cdd..8b1753939299 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -9134,6 +9134,7 @@ enum skl_power_gate {
>  #define _DP_TP_CTL_B			0x64140
>  #define DP_TP_CTL(port) _MMIO_PORT(port, _DP_TP_CTL_A, _DP_TP_CTL_B)
>  #define  DP_TP_CTL_ENABLE			(1 << 31)
> +#define  DP_TP_CTL_FEC_ENABLE			(1 << 30)
>  #define  DP_TP_CTL_MODE_SST			(0 << 27)
>  #define  DP_TP_CTL_MODE_MST			(1 << 27)
>  #define  DP_TP_CTL_FORCE_ACT			(1 << 25)
> @@ -9152,6 +9153,7 @@ enum skl_power_gate {
>  #define _DP_TP_STATUS_A			0x64044
>  #define _DP_TP_STATUS_B			0x64144
>  #define DP_TP_STATUS(port) _MMIO_PORT(port, _DP_TP_STATUS_A, _DP_TP_STATUS_B)
> +#define  DP_TP_STATUS_FEC_ENABLE_LIVE		(1 << 28)
>  #define  DP_TP_STATUS_IDLE_DONE			(1 << 25)
>  #define  DP_TP_STATUS_ACT_SENT			(1 << 24)
>  #define  DP_TP_STATUS_MODE_STATUS_MST		(1 << 23)
> diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c
> index efbada95dc4e..f03f44f332c7 100644
> --- a/drivers/gpu/drm/i915/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/intel_ddi.c
> @@ -2889,6 +2889,32 @@ static void intel_ddi_clk_disable(struct intel_encoder *encoder)
>  	}
>  }
>  
> +void intel_dp_enable_fec_state(struct intel_dp *intel_dp,
> +			       const struct intel_crtc_state *crtc_state)

Can be static. intel_ddi_enable_fec() seems like a better name,
and we can just pass the intel_encoder to this I think. No need to 
do all the "intel_dp to encoder" gynmastics then.

> +{
> +	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
> +	struct intel_digital_port *intel_dig_port = dp_to_dig_port(intel_dp);
> +	enum port port = intel_dig_port->base.port;
> +	u32 val;
> +
> +	/* FEC support exists for DP 1.4 only */

This comment is misleading. There are other reasons besides < DP 1.4 for
not using FEC. IMO just drop the comment.

> +	if (!crtc_state->fec_enable)
> +		return;
> +
> +	if (!crtc_state->dsc_params.compression_enable)
> +		return;

That check can be removed now.

> +
> +	val = I915_READ(DP_TP_CTL(port));
> +	val |= DP_TP_CTL_FEC_ENABLE;
> +	I915_WRITE(DP_TP_CTL(port), val);
> +
> +	if (intel_wait_for_register(dev_priv, DP_TP_STATUS(port),
> +				    DP_TP_STATUS_FEC_ENABLE_LIVE,
> +				    DP_TP_STATUS_FEC_ENABLE_LIVE,
> +				    1))
> +		DRM_ERROR("Timed out waiting for FEC Enable Status\n");
> +}
> +
>  static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  				    const struct intel_crtc_state *crtc_state,
>  				    const struct drm_connector_state *conn_state)
> @@ -2934,9 +2960,13 @@ static void intel_ddi_pre_enable_dp(struct intel_encoder *encoder,
>  					      DP_DECOMPRESSION_EN);
>  	intel_dp_sink_set_fec_ready(intel_dp, crtc_state, DP_FEC_READY);
>  	intel_dp_start_link_train(intel_dp);
> +

Unrelated whitespace change.

>  	if (port != PORT_A || INTEL_GEN(dev_priv) >= 9)
>  		intel_dp_stop_link_train(intel_dp);
>  
> +	/* Set FEC state after link training */

Redundant comment.

> +	intel_dp_enable_fec_state(intel_dp, crtc_state);
> +
>  	icl_enable_phy_clock_gating(dig_port);
>  
>  	if (!is_mst)
> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> index 2a080205968d..1cdfa9c5da43 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1799,6 +1799,8 @@ void intel_dp_sink_set_decompression_state(struct intel_dp *intel_dp,
>  void intel_dp_sink_set_fec_ready(struct intel_dp *intel_dp,
>  				 const struct intel_crtc_state *crtc_state,
>  				 int state);
> +void intel_dp_enable_fec_state(struct intel_dp *intel_dp,
> +			       const struct intel_crtc_state *crtc_state);
>  void intel_dp_encoder_reset(struct drm_encoder *encoder);
>  void intel_dp_encoder_suspend(struct intel_encoder *intel_encoder);
>  void intel_dp_encoder_destroy(struct drm_encoder *encoder);
> -- 
> 2.17.1

-- 
Ville Syrjälä
Intel
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