Re: RFC: [PATCH v2] can: flexcan: Implement errata ERR005829

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 09/16/2014 02:28 PM, David Jander wrote:

>>> Please note that if the silicon bug didn't exist, none of the two writes
>>> would be necessary.
>>> Once you create a quirk for this, how are we supposed to know which
>>> versions need this quirk, and which don't? Can we trust the existence of
>>> erratas for the different i.MX Soc's, and should we just go and check them
>>> all?
>>
>> I had a patch with the quirk, but I removed it, as you suggested, just
>> in case.
> 
> I did not directly suggest to NOT use a quirk, I only had some concerns. In

Not directly, but between the lines :D

> the meantime I have checked a few of the SoCs for erratas, and found this
> errata only for i.MX6 and Vybrid VF6xx, which makes me suspect this problem is
> unique to IP version 10 (if the IP version table at the beginning of the
> source-code is to be trusted).

We don't even know the IP version of the flexcan core on the vybrid, it
has different features than the imx6 one.

> OTOH, if you decided to leave the unconditional writes in there, I am fine
> with that. I don't think they do much harm.
> 
> Is it time to revisit my other patch(es) yet? If so, from where should I pull
> the base?

Sorry, no time yet, but I've found another (luckily only a minor)
problem with the mailboxes. After sending a RTR frame the TX mailbox
gets automatically converted into a RX one.

See imx6 data sheet Table 26-5. Message Buffer Code for Tx buffers:

> Transmit remote request frame unconditionally once. After
> transmission, the MB automatically becomes an Rx Empty MB
> with the same ID.

I'll prepare a patch.

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
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