From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Cc: linux-can@vger.kernel.org, "Stefan Mätje" <Stefan.Maetje@esd.eu>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 2/7] can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}_min
Date: Mon, 16 Aug 2021 10:42:35 +0200 [thread overview]
Message-ID: <20210816084235.fr7fzau2ce7zl4d4@pengutronix.de> (raw)
In-Reply-To: <20210815033248.98111-3-mailhol.vincent@wanadoo.fr>
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On 15.08.2021 12:32:43, Vincent Mailhol wrote:
> ISO 11898-1 specifies in section 11.3.3 "Transmitter delay
> compensation" that "the configuration range for [the] SSP position
> shall be at least 0 to 63 minimum time quanta."
>
> Because SSP = TDCV + TDCO, it means that we should allow both TDCV and
> TDCO to hold zero value in order to honor SSP's minimum possible
> value.
>
> However, current implementation assigned special meaning to TDCV and
> TDCO's zero values:
> * TDCV = 0 -> TDCV is automatically measured by the transceiver.
> * TDCO = 0 -> TDC is off.
>
> In order to allow for those values to really be zero and to maintain
> current features, we introduce two new flags:
> * CAN_CTRLMODE_TDC_AUTO indicates that the controller support
> automatic measurement of TDCV.
> * CAN_CTRLMODE_TDC_MANUAL indicates that the controller support
> manual configuration of TDCV. N.B.: current implementation failed
> to provide an option for the driver to indicate that only manual
> mode was supported.
>
> TDC is disabled if both CAN_CTRLMODE_TDC_AUTO and
> CAN_CTRLMODE_TDC_MANUAL flags are off, c.f. the helper function
> can_tdc_is_enabled() which is also introduced in this patch.
Nitpick: We can only say that TDC is disabled, if the driver supports
the TDC interface at all, which is the case if tdc_const is set.
> Also, this patch adds three fields: tdcv_min, tdco_min and tdcf_min to
> struct can_tdc_const. While we are not convinced that those three
> fields could be anything else than zero, we can imagine that some
> controllers might specify a lower bound on these. Thus, those minimums
> are really added "just in case".
I'm not sure, if we talked about the mcp251xfd's tcdo, valid values are
-64...63.
Marc
--
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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next prev parent reply other threads:[~2021-08-16 8:42 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-15 3:32 [PATCH v5 0/7] add the netlink interface for CAN-FD Transmitter Delay Compensation (TDC) Vincent Mailhol
2021-08-15 3:32 ` [PATCH v5 1/7] can: netlink: allow user to turn off unsupported features Vincent Mailhol
2021-08-19 7:45 ` Marc Kleine-Budde
2021-08-19 9:24 ` Vincent MAILHOL
2021-08-19 10:07 ` Marc Kleine-Budde
2021-08-15 3:32 ` [PATCH v5 2/7] can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}_min Vincent Mailhol
2021-08-16 8:42 ` Marc Kleine-Budde [this message]
2021-08-16 10:24 ` Vincent MAILHOL
2021-08-16 12:25 ` Marc Kleine-Budde
2021-08-16 12:33 ` Marc Kleine-Budde
2021-08-16 13:43 ` Marc Kleine-Budde
2021-08-16 15:49 ` Vincent MAILHOL
2021-08-16 16:04 ` Vincent MAILHOL
2021-08-17 1:12 ` Vincent MAILHOL
2021-08-17 20:01 ` Marc Kleine-Budde
2021-08-18 9:22 ` Vincent MAILHOL
2021-08-18 12:29 ` Marc Kleine-Budde
2021-08-18 14:17 ` Vincent MAILHOL
2021-08-20 6:12 ` Vincent MAILHOL
2021-08-16 14:10 ` Vincent MAILHOL
2021-08-16 14:30 ` Marc Kleine-Budde
2021-08-17 9:43 ` Marc Kleine-Budde
2021-08-16 13:49 ` Stefan Mätje
2021-08-16 15:56 ` Vincent MAILHOL
2021-08-15 3:32 ` [PATCH v5 3/7] can: bittiming: change unit of TDC parameters to clock periods Vincent Mailhol
2021-08-15 3:32 ` [PATCH v5 4/7] can: dev: add can_tdc_get_relative_tdco() helper function Vincent Mailhol
2021-08-16 11:27 ` Marc Kleine-Budde
2021-08-15 3:32 ` [PATCH v5 5/7] can: netlink: add interface for CAN-FD Transmitter Delay Compensation (TDC) Vincent Mailhol
2021-08-17 19:55 ` Marc Kleine-Budde
2021-08-18 8:08 ` Vincent MAILHOL
2021-08-18 8:19 ` Marc Kleine-Budde
2021-08-18 8:37 ` Vincent MAILHOL
2021-08-18 8:43 ` Marc Kleine-Budde
2021-08-15 3:32 ` [PATCH v5 6/7] can: netlink: add can_priv::do_get_auto_tdcv() to retrieve tdcv from device Vincent Mailhol
2021-08-15 3:32 ` [PATCH v5 7/7] can: etas_es58x: clean-up documentation of struct es58x_fd_tx_conf_msg Vincent Mailhol
2021-08-19 10:08 ` Marc Kleine-Budde
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