[PATCH 09/15] drm/dp: Add helper to get post-cursor adjustments

[Lyude Paul]

Reviewed-by: Lyude Paul <lyude at redhat.com>

On Tue, 2019-10-15 at 16:35 +0200, Thierry Reding wrote:
> From: Thierry Reding <treding at nvidia.com>
> 
> If the transmitter supports pre-emphasis post cursor2 the sink will
> request adjustments in a similar way to how it requests adjustments to
> the voltage swing and pre-emphasis settings.
> 
> Add a helper to extract these adjustments on a per-lane basis from the
> DPCD link status.
> 
> Reviewed-by: Philipp Zabel <p.zabel at pengutronix.de>
> Signed-off-by: Thierry Reding <treding at nvidia.com>
> ---
>  drivers/gpu/drm/drm_dp_helper.c | 10 ++++++++++
>  include/drm/drm_dp_helper.h     | 10 ++++++++++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_helper.c
> b/drivers/gpu/drm/drm_dp_helper.c
> index 4b66010771fa..de8ff8ddb445 100644
> --- a/drivers/gpu/drm/drm_dp_helper.c
> +++ b/drivers/gpu/drm/drm_dp_helper.c
> @@ -120,6 +120,16 @@ 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);
>  
> +u8 drm_dp_get_adjust_request_post_cursor(const u8
> link_status[DP_LINK_STATUS_SIZE],
> +					 unsigned int lane)
> +{
> +	unsigned int offset = DP_ADJUST_REQUEST_POST_CURSOR2;
> +	u8 value = dp_link_status(link_status, offset);
> +
> +	return (value >> (lane << 1)) & 0x3;
> +}
> +EXPORT_SYMBOL(drm_dp_get_adjust_request_post_cursor);
> +
>  void drm_dp_link_train_clock_recovery_delay(const u8
> dpcd[DP_RECEIVER_CAP_SIZE])
>  {
>  	unsigned int rd_interval = drm_dp_aux_rd_interval(dpcd);
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 6c12de6f7e46..e0b2c03f3cbb 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -608,6 +608,14 @@
>  # define DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT  6
>  
>  #define DP_ADJUST_REQUEST_POST_CURSOR2      0x20c
> +# define DP_ADJUST_POST_CURSOR2_LANE0_MASK  0x03
> +# define DP_ADJUST_POST_CURSOR2_LANE0_SHIFT 0
> +# define DP_ADJUST_POST_CURSOR2_LANE1_MASK  0x0c
> +# define DP_ADJUST_POST_CURSOR2_LANE1_SHIFT 2
> +# define DP_ADJUST_POST_CURSOR2_LANE2_MASK  0x30
> +# define DP_ADJUST_POST_CURSOR2_LANE2_SHIFT 4
> +# define DP_ADJUST_POST_CURSOR2_LANE3_MASK  0xc0
> +# define DP_ADJUST_POST_CURSOR2_LANE3_SHIFT 6
>  
>  #define DP_TEST_REQUEST			    0x218
>  # define DP_TEST_LINK_TRAINING		    (1 << 0)
> @@ -1121,6 +1129,8 @@ 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_request_post_cursor(const u8
> link_status[DP_LINK_STATUS_SIZE],
> +					 unsigned int lane);
>  
>  #define DP_BRANCH_OUI_HEADER_SIZE	0xc
>  #define DP_RECEIVER_CAP_SIZE		0xf
-- 
Cheers,
	Lyude Paul