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@lists.freedesktop.org
> Signed-off-by: Jani Nikula <jani.nik...@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrj...@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
