From: Torin Cooper-Bennun <torin@maxiluxsystems.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: linux-can@vger.kernel.org
Subject: Re: can, tcan4x5x: look to merge rpi support into rpi kernel tree
Date: Fri, 26 Feb 2021 16:14:34 +0000 [thread overview]
Message-ID: <20210226161434.ymdrmclic6nrccj5@bigthink> (raw)
In-Reply-To: <20210226160135.w43onb3z25xhv4re@pengutronix.de>
On Fri, Feb 26, 2021 at 05:01:35PM +0100, Marc Kleine-Budde wrote:
> > Is timestamp-wrapping a concern for rx-offloading?
>
> No, as long as you provide a proper u32 timestamp, which means wrap
> around at 0xffffffff to 0x0. As the tcan4x5x has only a 16 bit
> timestamp, shift it to full 32 bit, like this:
>
> https://elixir.bootlin.com/linux/v5.11/source/drivers/net/can/flexcan.c#L805
>
> On the mcp with true 32 bit timestamp there's a wraparound every 107
> seconds at 40 MHz external clock (0xffffffff / 40000000).
>
> The tcan has the TSS.TCP as a prescaler and increments in bit time,
> which is 5MHz max. This results in a wrap around every 13ms (0xffff /
> 5000000) with a prescaler of 1. With a prescaler of 16, you can increase
> this to 209ms (0xffff / 5000000 * 16), which gives an accuracy of 2
> bytes.
Nice, thank you, that all sounds good. I'll get to work. :)
--
Regards,
Torin Cooper-Bennun
Software Engineer | maxiluxsystems.com
prev parent reply other threads:[~2021-02-26 16:15 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <602651f9.1c69fb81.302a5.647d@mx.google.com>
[not found] ` <20210215144509.rhds7oybzat6u27w@hardanger.blackshift.org>
[not found] ` <CAALJrqgrmzGHZX+iiMYwMkVMpxtf_3fWYkVA-iMdPOxpGzrCRQ@mail.gmail.com>
2021-02-15 17:44 ` can, tcan4x5x: look to merge rpi support into rpi kernel tree Marc Kleine-Budde
2021-02-16 9:06 ` Torin Cooper-Bennun
2021-02-16 9:13 ` Marc Kleine-Budde
2021-02-16 9:44 ` Torin Cooper-Bennun
2021-02-16 10:28 ` Marc Kleine-Budde
[not found] ` <CAALJrqiVdmLQr7q2ijbWq70RD6PTD8PtVX_zmLW9=uNdc57WqA@mail.gmail.com>
2021-02-16 11:19 ` Marc Kleine-Budde
2021-02-16 11:38 ` Torin Cooper-Bennun
2021-02-16 12:32 ` Marc Kleine-Budde
2021-02-26 12:27 ` Torin Cooper-Bennun
2021-02-26 12:28 ` Marc Kleine-Budde
2021-02-26 12:18 ` Torin Cooper-Bennun
2021-02-26 12:22 ` Marc Kleine-Budde
2021-02-26 12:31 ` Torin Cooper-Bennun
2021-02-26 12:40 ` Marc Kleine-Budde
2021-02-26 13:26 ` Torin Cooper-Bennun
2021-02-26 13:39 ` Marc Kleine-Budde
2021-02-26 13:45 ` Torin Cooper-Bennun
2021-02-26 14:00 ` Marc Kleine-Budde
2021-02-26 15:26 ` Torin Cooper-Bennun
2021-02-26 16:01 ` Marc Kleine-Budde
2021-02-26 16:14 ` Torin Cooper-Bennun [this message]
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