netdev - Re: [net-next 6/6] can: mcp251xfd: mcp251xfd_regmap_crc_read(): work around broken CRC on TBC register

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Message-ID: <20211209112748.yixzz4xskw6qm7bw@pengutronix.de>
Date:   Thu, 9 Dec 2021 12:27:48 +0100
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Sven Schuchmann <schuchmann@...leissheimer.de>
Cc:     "Thomas.Kopp@...rochip.com" <Thomas.Kopp@...rochip.com>,
        "pavel.modilaynen@...vocars.com" <pavel.modilaynen@...vocars.com>,
        "drew@...gleboard.org" <drew@...gleboard.org>,
        "linux-can@...r.kernel.org" <linux-can@...r.kernel.org>,
        "menschel.p@...teo.de" <menschel.p@...teo.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "will@...china.cc" <will@...china.cc>
Subject: Re: [net-next 6/6] can: mcp251xfd: mcp251xfd_regmap_crc_read(): work
 around broken CRC on TBC register

On 09.12.2021 11:17:09, Sven Schuchmann wrote:
> we are also seeing the CRC Errors in our setup (rpi4, Kernel 5.10.x)
> from time to time. I just wanted to post here what I am seeing, maybe
> it helps...
> 
> [    6.761711] spi_master spi1: will run message pump with realtime priority
> [    6.778063] mcp251xfd spi1.0 can1: MCP2518FD rev0.0 (-RX_INT -MAB_NO_WARN +CRC_REG +CRC_RX +CRC_TX +ECC -HD c:40.00MHz m:20.00MHz r:17.00MHz e:16.66MHz) successfully initialized.
> 
> [ 4327.107856] mcp251xfd spi1.0 canfd1: CRC read error at address 0x0010 (length=4, data=00 cc 62 c4, CRC=0xa3a0) retrying.
> [ 7770.163335] mcp251xfd spi1.0 canfd1: CRC read error at address 0x0010 (length=4, data=00 bf 16 d5, CRC=0x9d3c) retrying.
> [ 8000.565955] mcp251xfd spi1.0 canfd1: CRC read error at address 0x0010 (length=4, data=00 40 66 fa, CRC=0x31d7) retrying.
> [ 9753.658173] mcp251xfd spi1.0 canfd1: CRC read error at address 0x0010 (length=4, data=80 e9 01 4e, CRC=0xe862) retrying.

You are using the a back port of my HW timestamp in your v5.10 branch.
So every 45 seconds the TBC register (address 0x0010) is read,
additionally for every CAN error frame.

In the mean time, I've implemented a workaround for the CRC read errors:

| c7eb923c3caf can: mcp251xfd: mcp251xfd_regmap_crc_read(): work around broken CRC on TBC register
| ef7a8c3e7599 can: mcp251xfd: mcp251xfd_regmap_crc_read_one(): Factor out crc check into separate function

It fixes the CRC read error, if the first data byte is 0x00 or 0x80.

These messages should disappear, if you cherry-pick the above patches.

regards,
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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