[PATCH 04/17] drm/dp: add helper for extracting adjust 128b/132b TX FFE preset

[Ville Syrjälä]

On Wed, Aug 18, 2021 at 09:10:39PM +0300, Jani Nikula wrote:
> The DP 2.0 128b/132b channel coding uses TX FFE presets instead of
> vswing and pre-emphasis.
> 
> Cc: dri-devel at lists.freedesktop.org
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>

Reviewed-by: Ville Syrjälä <ville.syrjala at linux.intel.com>

> ---
>  drivers/gpu/drm/drm_dp_helper.c | 14 ++++++++++++++
>  include/drm/drm_dp_helper.h     |  2 ++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
> index 9389f92cb944..2843238a78e6 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -130,6 +130,20 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI
>  }
>  EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
>  
> +/* DP 2.0 128b/132b */
> +u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE],
> +				   int lane)
> +{
> +	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
> +	int s = ((lane & 1) ?
> +		 DP_ADJUST_TX_FFE_PRESET_LANE1_SHIFT :
> +		 DP_ADJUST_TX_FFE_PRESET_LANE0_SHIFT);
> +	u8 l = dp_link_status(link_status, i);
> +
> +	return (l >> s) & 0xf;
> +}
> +EXPORT_SYMBOL(drm_dp_get_adjust_tx_ffe_preset);
> +
>  u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE],
>  					 unsigned int lane)
>  {
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index f3a61341011d..3ee0b3ffb8a5 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -1494,6 +1494,8 @@ u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
>  				     int lane);
>  u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
>  					  int lane);
> +u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE],
> +				   int lane);
>  u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE],
>  					 unsigned int lane);
>  
> -- 
> 2.20.1

-- 
Ville Syrjälä
Intel