On 05.03.2021 17:20:14, Torin Cooper-Bennun wrote:
> This is a prerequisite for transitioning the m_can driver to rx-offload,
> which works best with TX and RX timestamps.
>
> The timestamps provided by M_CAN are 16-bit, timed according to the
> nominal bit timing, and may be prescaled by a multiplier up to 16. We
> choose the highest prescalar so that the timestamp wraps every 2^20 bit
> times, or 209 ms at a bus speed of 5 Mbit/s. Timestamps will have a
> precision of 16 bit times.
>
> Signed-off-by: Torin Cooper-Bennun <torin@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/net/can/m_can/m_can.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/net/can/m_can/m_can.c b/drivers/net/can/m_can/m_can.c
> index ea79cf0640a8..83a673417e7c 100644
> --- a/drivers/net/can/m_can/m_can.c
> +++ b/drivers/net/can/m_can/m_can.c
> @@ -1139,6 +1139,7 @@ static int m_can_set_bittiming(struct net_device *dev)
> * - >= v3.1.x: TX FIFO is used
> * - configure mode
> * - setup bittiming
> + * - configure timestamp generation
> */
> static void m_can_chip_config(struct net_device *dev)
> {
> @@ -1250,6 +1251,11 @@ static void m_can_chip_config(struct net_device *dev)
> /* set bittiming params */
> m_can_set_bittiming(dev);
>
> + /* enable internal timestamp generation, with a prescalar of 16. The
> + * prescalar is applied to the nominal bit timing */
> + m_can_write(cdev, M_CAN_TSCC,
> + (0xf << TSCC_TCP_SHIFT) | TSCC_TSS_INTERNAL);
FIELD_PREP(TSCC_TCP_MASK, 0xf)
Marc
--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
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Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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