On Wed. 16 Jun 2021 at 18:54, Marc Kleine-Budde <mkl@xxxxxxxxxxxxxx> wrote: > On 24.02.2021 09:20:04, 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. > > > > This issue is addressed in ISO 11898-1 section 11.3.3 "Transmitter > > delay compensation" (TDC). > > > > This patch adds two new structures: can_tdc and can_tdc_const in order > > to implement this TDC. > > > > The structures are then added to can_priv. > > > > A controller supports TDC if an only if can_priv::tdc_const is not > > NULL. > > > > TDC is active if and only if: > > - fd flag is on > > - can_priv::tdc.tdco is not zero. > > It is the driver responsibility to check those two conditions are met. > > > > No new controller modes are introduced (i.e. no CAN_CTRL_MODE_TDC) in > > order not to be redundant with above logic. > > > > The names of the parameters are chosen to match existing CAN > > controllers specification. References: > > - Bosch C_CAN FD8: > > https://www.bosch-semiconductors.com/media/ip_modules/pdf_2/c_can_fd8/users_manual_c_can_fd8_r210_1.pdf > > - Microchip CAN FD Controller Module: > > http://ww1.microchip.com/downloads/en/DeviceDoc/MCP251XXFD-CAN-FD-Controller-Module-Family-Reference-Manual-20005678B.pdf > > - SAM E701/S70/V70/V71 Family: > > https://www.mouser.com/datasheet/2/268/60001527A-1284321.pdf > > > > Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> > > --- > > include/linux/can/bittiming.h | 65 +++++++++++++++++++++++++++++++++++ > > include/linux/can/dev.h | 3 ++ > > 2 files changed, 68 insertions(+) > > > > diff --git a/include/linux/can/bittiming.h b/include/linux/can/bittiming.h > > index 707575c668f4..91bf9f8926a7 100644 > > --- a/include/linux/can/bittiming.h > > +++ b/include/linux/can/bittiming.h > > @@ -1,5 +1,6 @@ > > /* SPDX-License-Identifier: GPL-2.0-only */ > > /* Copyright (c) 2020 Pengutronix, Marc Kleine-Budde <kernel@xxxxxxxxxxxxxx> > > + * Copyright (c) 2021 Vincent Mailhol <mailhol.vincent@xxxxxxxxxx> > > */ > > > > #ifndef _CAN_BITTIMING_H > > @@ -10,6 +11,70 @@ > > > > #define CAN_SYNC_SEG 1 > > > > +/* > > + * struct can_tdc - CAN FD Transmission Delay Compensation parameters > > + * > > + * 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. > > + * > > + * To solve this issue, ISO 11898-1 introduces in section 11.3.3 > > + * "Transmitter delay compensation" a SSP (Secondary Sample Point) > > + * equal to the distance, in time quanta, from the start of the bit > > + * time on the TX pin to the actual measurement on the RX pin. > > + * > > + * This structure contains the parameters to calculate that SSP. > > + * > > + * @tdcv: Transmitter Delay Compensation Value. Distance, in time > > + * quanta, from when the bit is sent on the TX pin to when it is > > + * received on the RX pin of the transmitter. Possible options: > > + * > > + * O: automatic mode. The controller dynamically measure @tdcv > ^ > > I think this is supposed to be a 0, not a O? > I'll send a patch Absolutely. I am not sure how I did such a mistake. I was probably not fully awake as there are two other grammar issues there. I sent another patch to fix those. Yours sincerely, Vincent
