Re: [PATCH V4] drm: Add LTTPR defines for DP 1.4a

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Sep 04, 2019 at 07:02:18PM +0000, Siqueira, Rodrigo wrote:
> DP 1.4a specification defines Link Training Tunable PHY Repeater (LTTPR)

A bunch of this stuff was already in DP 1.3 so the statement here
(and in the comment) is a bit misleading.

"LTTPR" is not a name that appears anywhere in the spec AFAICS, so
calling it that is a bit confusing.

> which is required to add support for systems with Thunderbolt or other
> repeater devices.

"required" seems a bit strong. IIRC by default these things should be in
transparent mode so the DPTX can remain blissfully unaware of their
presence.

> 
> Changes since V3:
> - Replace spaces by tabs
> Changes since V2:
> - Drop the kernel-doc comment
> - Reorder LTTPR according to register offset
> Changes since V1:
> - Adjusts registers names to be aligned with spec and the rest of the
>   file
> - Update spec comment from 1.4 to 1.4a
> 
> Cc: Abdoulaye Berthe <Abdoulaye.Berthe@amd.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Leo Li <sunpeng.li@amd.com>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Cc: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
> Signed-off-by: Abdoulaye Berthe <Abdoulaye.Berthe@amd.com>
> Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
> ---
>  include/drm/drm_dp_helper.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
> index 8364502f92cf..5abed96a1cb1 100644
> --- a/include/drm/drm_dp_helper.h
> +++ b/include/drm/drm_dp_helper.h
> @@ -966,6 +966,31 @@
>  #define DP_HDCP_2_2_REG_STREAM_TYPE_OFFSET	0x69494
>  #define DP_HDCP_2_2_REG_DBG_OFFSET		0x69518
>  
> +/* Link Training (LT)-tunable Physical Repeaters - DP 1.4a */

s/Physical/PHY/ to match the spec.

> +#define DP_LT_TUNABLE_PHY_REPEATER_FIELD_DATA_STRUCTURE_REV	0xf0000
> +#define DP_MAX_LINK_RATE_PHY_REPEATER				0xf0001
> +#define DP_PHY_REPEATER_CNT					0xf0002
> +#define DP_PHY_REPEATER_MODE					0xf0003
> +#define DP_MAX_LANE_COUNT_PHY_REPEATER				0xf0004
> +#define DP_PHY_REPEATER_EXTENDED_WAIT_TIMEOUT			0xf0005

The last two are DP 1.4a it seems.

0xf0004 was called Repeater_FEC_CAPABILITY in 1.4. But the spec doesn't
say anything about the DPCD revision so I have no idea how you're
supposed to decide which definition to use.

DP 1.4a seems to have added FEC_CAPABILITY_PHY_REPEATER1 at 0xf0294.
To replace the 1.4 Repeater_FEC_CAPABILITY I suppose.

> +#define DP_TRAINING_PATTERN_SET_PHY_REPEATER1			0xf0010
> +#define DP_TRAINING_LANE0_SET_PHY_REPEATER1			0xf0011
> +#define DP_TRAINING_LANE1_SET_PHY_REPEATER1			0xf0012
> +#define DP_TRAINING_LANE2_SET_PHY_REPEATER1			0xf0013
> +#define DP_TRAINING_LANE3_SET_PHY_REPEATER1			0xf0014
> +#define DP_TRAINING_AUX_RD_INTERVAL_PHY_REPEATER1		0xf0020
> +#define DP_TRANSMITTER_CAPABILITY_PHY_REPEATER1			0xf0021

Above two are DP 1.4a.

> +#define DP_LANE0_1_STATUS_PHY_REPEATER1				0xf0030
> +#define DP_LANE2_3_STATUS_PHY_REPEATER1				0xf0031
> +#define DP_LANE_ALIGN_STATUS_UPDATED_PHY_REPEATER1		0xf0032
> +#define DP_ADJUST_REQUEST_LANE0_1_PHY_REPEATER1			0xf0033
> +#define DP_ADJUST_REQUEST_LANE2_3_PHY_REPEATER1			0xf0034
> +#define DP_SYMBOL_ERROR_COUNT_LANE0_PHY_REPEATER1		0xf0035
> +#define DP_SYMBOL_ERROR_COUNT_LANE1_PHY_REPEATER1		0xf0037
> +#define DP_SYMBOL_ERROR_COUNT_LANE2_PHY_REPEATER1		0xf0039
> +#define DP_SYMBOL_ERROR_COUNT_LANE3_PHY_REPEATER1		0xf003b
> +#define DP_FEC_STATUS_PHY_REPEATER1				0xf0290

This seems to have appared in DP 1.4.

You skipped quite a few registers here. I guess those were deemed not
important?

> +
>  /* DP HDCP message start offsets in DPCD address space */
>  #define DP_HDCP_2_2_AKE_INIT_OFFSET		DP_HDCP_2_2_REG_RTX_OFFSET
>  #define DP_HDCP_2_2_AKE_SEND_CERT_OFFSET	DP_HDCP_2_2_REG_CERT_RX_OFFSET
> -- 
> 2.23.0



-- 
Ville Syrjälä
Intel
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