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

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Date:   Thu, 22 Apr 2021 16:46:28 +0000
From:   Patrick Menschel <menschel.p@...teo.de>
To:     Marc Kleine-Budde <mkl@...gutronix.de>,
        Drew Fustini <drew@...gleboard.org>
Cc:     netdev@...r.kernel.org, linux-can@...r.kernel.org,
        kernel@...gutronix.de, Manivannan Sadhasivam <mani@...nel.org>,
        Will C <will@...china.cc>,
        Thomas Kopp <thomas.kopp@...rochip.com>
Subject: Re: [net-next 6/6] can: mcp251xfd: mcp251xfd_regmap_crc_read(): work
 around broken CRC on TBC register

Am 22.04.21 um 09:18 schrieb Marc Kleine-Budde:
> On 4/21/21 9:58 PM, Drew Fustini wrote:
>> I am encountering similar error with the 5.10 raspberrypi kernel on
>> RPi 4 with MCP2518FD:
>>
>>   mcp251xfd spi0.0 can0: CRC read error at address 0x0010 (length=4,
>> data=00 ad 58 67, CRC=0xbbfd) retrying
> 
> What's the situation you see these errors?
> 
> I'm not particular happy with that patch, as it only works around that one
> particular bit flip issue. If you really hammer the register, the driver will
> still notice CRC errors that can be explained by other bits flipping. Consider
> this as the first order approximation of a higher order problem :) - the root
> cause is still unknown.
> 
>> Would it be possible for you to pull these patches into a v5.10 branch
>> in your linux-rpi repo [1]?
> 
> Here you are:
> 
> https://github.com/marckleinebudde/linux-rpi/tree/v5.10-rpi/backport-performance-improvements
> 
> I've included the UINC performance enhancements, too. The branch is compiled
> tested only, though. I'll send a pull request to the rpi kernel after I've
> testing feedback from you.
> 
> regards,
> Marc
> 

I can also confirm these occasional CRC errors. I run a custom pytest
suite on a pi3b+ that uses isotp and bcm in parallel.
No CAN-FD, just 500k regular vehicle can for infotainment.

$ dmesg | grep CRC

[    8.198863] mcp251xfd spi0.1 can0: 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.

[    8.209159] mcp251xfd spi0.0 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.

[74264.462934] mcp251xfd spi0.0 mcp0: CRC read error at address 0x0010
(length=4, data=80 33 d2 8a, CRC=0x0e3e) retrying.

[74749.267977] mcp251xfd spi0.0 mcp0: CRC read error at address 0x0010
(length=4, data=80 1a ad 0e, CRC=0x8d17) retrying.

[591150.766153] mcp251xfd spi0.0 mcp0: CRC read error at address 0x0010
(length=4, data=80 3d b5 60, CRC=0x5e9c) retrying.


Best Regards,
Patrick