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

From: Drew Fustini <pdp7pdp7@gmail.com>
To: Marc Kleine-Budde <mkl@pengutronix.de>
Cc: Drew Fustini <drew@beagleboard.org>,
	netdev@vger.kernel.org,
	"linux-can@vger.kernel.org" <linux-can@vger.kernel.org>,
	Will C <will@macchina.cc>,
	menschel.p@posteo.de
Subject: Re: [net-next 6/6] can: mcp251xfd: mcp251xfd_regmap_crc_read(): work around broken CRC on TBC register
Date: Fri, 7 May 2021 15:36:32 -0700	[thread overview]
Message-ID: <CAEf4M_Dg5u=b+fYwXDUMRGSXeXHuo-bXZmzoAs2bW0kFncMSQg@mail.gmail.com> (raw)
In-Reply-To: <20210507072521.3y652xz2kmibjo7d@pengutronix.de>

On Fri, May 7, 2021 at 12:56 AM Marc Kleine-Budde <mkl@pengutronix.de> wrote:
>
> On 22.04.2021 09:18:54, Marc Kleine-Budde wrote:
> > 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.
>
> Drew, Patrick, have you tested this branch? If so I'll send a pull
> request to the raspi kernel.

Thank you for following up.

I need to build it and send it to the friend who was testing to check
if the CRC errors go away.  He is testing CANFD with a 2021 Ford F150
truck.  I will follow up here once I know the results.

-Drew