netdev - Re: [PATCH] can: xilinx_can: add support for RX timestamps on Zynq

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Date:   Mon, 18 Jul 2022 10:33:12 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Matej Vasilevski <matej.vasilevski@...nam.cz>
Cc:     Appana Durga Kedareswara rao <appana.durga.rao@...inx.com>,
        Naga Sureshkumar Relli <naga.sureshkumar.relli@...inx.com>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        linux-can@...r.kernel.org, netdev@...r.kernel.org,
        Martin Jerabek <martin.jerabek01@...il.com>
Subject: Re: [PATCH] can: xilinx_can: add support for RX timestamps on Zynq

On 16.07.2022 14:04:09, Matej Vasilevski wrote:
> This patch adds support for hardware RX timestamps from Xilinx Zynq CAN
> controllers. The timestamp is calculated against a timepoint reference
> stored when the first CAN message is received.
> 
> When CAN bus traffic does not contain long idle pauses (so that
> the clocks would drift by a multiple of the counter rollover time),
> then the hardware timestamps provide precise relative time between
> received messages. This can be used e.g. for latency testing.

Please make use of the existing cyclecounter/timecounter framework. Is
there a way to read the current time from a register? If so, please
setup a worker that does that regularly.

Have a look at the mcp251xfd driver as an example:

https://elixir.bootlin.com/linux/latest/source/drivers/net/can/spi/mcp251xfd/mcp251xfd-timestamp.c

Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
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