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Date:   Mon, 16 Aug 2021 10:12:05 +0200
From:   Marc Kleine-Budde <mkl@pengutronix.de>
To:     Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Cc:     Stephen Hemminger <stephen@networkplumber.org>,
        linux-can@vger.kernel.org,
        Stefan =?utf-8?B?TcOkdGpl?= <stefan.maetje@esd.eu>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 4/4] iplink_can: add new CAN FD bittiming parameters:
 Transmitter Delay Compensation (TDC)
Message-ID: <20210816081205.7rjdskaui35f3jml@pengutronix.de>
References: <20210814101728.75334-1-mailhol.vincent@wanadoo.fr>
 <20210814101728.75334-5-mailhol.vincent@wanadoo.fr>
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On 14.08.2021 19:17:28, Vincent Mailhol wrote:
> At high bit rates, the propagation delay from the TX pin to the RX pin
> of the transceiver causes measurement errors: the sample point on the
> RX pin might occur on the previous bit.
>=20
> This issue is addressed in ISO 11898-1 section 11.3.3 "Transmitter
> delay compensation" (TDC).
>=20
> This patch brings command line support to nine TDC parameters which
> were recently added to the kernel's CAN netlink interface in order to
> implement TDC:
>   - IFLA_CAN_TDC_TDCV_MIN: Transmitter Delay Compensation Value
>     minimum value
>   - IFLA_CAN_TDC_TDCV_MAX: Transmitter Delay Compensation Value
>     maximum value
>   - IFLA_CAN_TDC_TDCO_MIN: Transmitter Delay Compensation Offset
>     minimum value
>   - IFLA_CAN_TDC_TDCO_MAX: Transmitter Delay Compensation Offset
>     maximum value
>   - IFLA_CAN_TDC_TDCF_MIN: Transmitter Delay Compensation Filter
>     window minimum value
>   - IFLA_CAN_TDC_TDCF_MAX: Transmitter Delay Compensation Filter
>     window maximum value
>   - IFLA_CAN_TDC_TDCV: Transmitter Delay Compensation Value
>   - IFLA_CAN_TDC_TDCO: Transmitter Delay Compensation Offset
>   - IFLA_CAN_TDC_TDCF: Transmitter Delay Compensation Filter window
>=20
> All those new parameters are nested together into the attribute
> IFLA_CAN_TDC.
>=20
> A tdc-mode parameter allow to specify how to operate. Valid options
> are:
>=20
>   * auto: the transmitter automatically measures TDCV. As such, TDCV
>     values can not be manually provided. In this mode, the user must
>     specify TDCO and may also specify TDCF if supported.
>=20
>   * manual: Use the TDCV value provided by the user are used. In this
                           ^^^^^                      ^^^
                           singular                   plural
>     mode, the user must specify both TDCV and TDCO and may also
>     specify TDCF if supported.
>=20

Marc

--=20
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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