Re: [Intel-gfx] [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-de...@lists.freedesktop.org
> Signed-off-by: Jani Nikula 

Reviewed-by: Ville Syrjälä 

> ---
>  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

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

[Jani Nikula]

The DP 2.0 128b/132b channel coding uses TX FFE presets instead of
vswing and pre-emphasis.

Cc: dri-de...@lists.freedesktop.org
Signed-off-by: Jani Nikula 
---
 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