Re: [Intel-gfx] [PATCH 2/4] drm/i915: Call intel_ddi_init_dp_buf_reg() earlier

[Imre Deak <imre.deak@intel.com>]

On Thu, Sep 30, 2021 at 04:43:08PM +0300, Ville Syrjala wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> I want intel_dp->DP to be fully populated by the time the
> initial vswing programming happens. To that end move the
> intel_ddi_init_dp_buf_reg() call to an earlier spot.
> 
> Additionally we don't want intel_ddi_init_dp_buf_reg() to
> set DDI_BUF_CTL_ENABLE since the port should only get enabled
> at the start of link training (see intel_ddi_prepare_link_retrain()).
> So any earlier write to the register should not set the enable bit.
> 
> Cc: Imre Deak <imre.deak@intel.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 44 +++++++++++-------------
>  1 file changed, 21 insertions(+), 23 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 51d07e9af9f3..65e59f16879d 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -282,9 +282,10 @@ static void intel_ddi_init_dp_buf_reg(struct intel_encoder *encoder,
>  	struct intel_digital_port *dig_port = enc_to_dig_port(encoder);
>  	enum phy phy = intel_port_to_phy(i915, encoder->port);
>  
> +	/* DDI_BUF_CTL_ENABLE will be set by intel_ddi_prepare_link_retrain() later */
>  	intel_dp->DP = dig_port->saved_port_bits |
> -		DDI_BUF_CTL_ENABLE | DDI_BUF_TRANS_SELECT(0);
> -	intel_dp->DP |= DDI_PORT_WIDTH(crtc_state->lane_count);
> +		DDI_PORT_WIDTH(crtc_state->lane_count) |
> +		DDI_BUF_TRANS_SELECT(0);
>  
>  	if (IS_ALDERLAKE_P(i915) && intel_phy_is_tc(i915, phy)) {
>  		intel_dp->DP |= ddi_buf_phy_link_rate(crtc_state->port_clock);
> @@ -2360,6 +2361,12 @@ static void dg2_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  	intel_dp_set_link_params(intel_dp, crtc_state->port_clock,
>  				 crtc_state->lane_count);
>  
> +	/*
> +	 * We only configure what the register value will be here.  Actual
> +	 * enabling happens during link training farther down.
> +	 */
> +	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
> +
>  	/*
>  	 * 1. Enable Power Wells
>  	 *
> @@ -2416,16 +2423,6 @@ static void dg2_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  	/* 5.e Configure voltage swing and related IO settings */
>  	intel_snps_phy_ddi_vswing_sequence(encoder, crtc_state, level);
>  
> -	/*
> -	 * 5.f Configure and enable DDI_BUF_CTL
> -	 * 5.g Wait for DDI_BUF_CTL DDI Idle Status = 0b (Not Idle), timeout
> -	 *     after 1200 us.
> -	 *
> -	 * We only configure what the register value will be here.  Actual
> -	 * enabling happens during link training farther down.
> -	 */
> -	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
> -
>  	if (!is_mst)
>  		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
>  
> @@ -2473,6 +2470,12 @@ static void tgl_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  				 crtc_state->port_clock,
>  				 crtc_state->lane_count);
>  
> +	/*
> +	 * We only configure what the register value will be here.  Actual
> +	 * enabling happens during link training farther down.
> +	 */
> +	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
> +
>  	/*
>  	 * 1. Enable Power Wells
>  	 *
> @@ -2554,16 +2557,6 @@ static void tgl_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  	 */
>  	intel_ddi_mso_configure(crtc_state);
>  
> -	/*
> -	 * 7.g Configure and enable DDI_BUF_CTL
> -	 * 7.h Wait for DDI_BUF_CTL DDI Idle Status = 0b (Not Idle), timeout
> -	 *     after 500 us.
> -	 *
> -	 * We only configure what the register value will be here.  Actual
> -	 * enabling happens during link training farther down.
> -	 */
> -	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
> -
>  	if (!is_mst)
>  		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
>  
> @@ -2620,6 +2613,12 @@ static void hsw_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  				 crtc_state->port_clock,
>  				 crtc_state->lane_count);
>  
> +	/*
> +	 * We only configure what the register value will be here.  Actual
> +	 * enabling happens during link training farther down.
> +	 */
> +	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
> +
>  	intel_pps_on(intel_dp);
>  
>  	intel_ddi_enable_clock(encoder, crtc_state);
> @@ -2641,7 +2640,6 @@ static void hsw_ddi_pre_enable_dp(struct intel_atomic_state *state,
>  
>  	intel_ddi_power_up_lanes(encoder, crtc_state);
>  
> -	intel_ddi_init_dp_buf_reg(encoder, crtc_state);
>  	if (!is_mst)
>  		intel_dp_set_power(intel_dp, DP_SET_POWER_D0);
>  	intel_dp_configure_protocol_converter(intel_dp, crtc_state);
> -- 
> 2.32.0
>