Re: [PATCH 1/3] can: flexcan.c: Correctly initialize mailboxes

[David Jander <david@protonic.nl>]

On Tue, 02 Sep 2014 12:24:28 +0200
Marc Kleine-Budde <mkl@pengutronix.de> wrote:

> On 08/27/2014 11:58 AM, David Jander wrote:
> > Apparently mailboxes may contain random data at startup, causing some of
> > them being prepared for message reception. This causes overruns being
> > missed or even confusing the IRQ check for trasmitted messages, increasing
> > the transmit counter instead of the error counter.
> > 
> > Signed-off-by: David Jander <david@protonic.nl>
> 
> Before patch
> 
> 0d1862e can: flexcan: fix flexcan_chip_start() on imx6
> 
> there was a loop clearing the whole cantxfg register space. But this
> turned out to be bogus, as message buffers 1...7 are reserved by the
> FIFO engine and we're not allowed to tough them. This lead to some kind
> of abort on imx6.
> 
> You may need this patch once you don't make use of the FIFO engine any more.

You will need this patch in either case, but indeed, if you use the FIFO, you
should skip the MB's that are shadowed by the FIFO.
If you don't clear the rest of the MB's they may still contain random data and
the problem remains.
IMHO 0d1862e is wrong, since buffers are not in reset default values. There is
no indication of that in the reference manual, and I have observed that they
are indeed not cleared after reset.

Best regards,

-- 
David Jander
Protonic Holland.