Re: [RESEND] [PATCH] net: CAN: at91_can.c: decrease likelyhood of RX overruns

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

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On 10/06/2014 01:39 PM, David Jander wrote:
[...]
>>>> And the same with 500kBit/s:
>>>> plain:      0, 0, lockup
>>>> your patch: 0, 0, 0
>>>> rx-fifo:    0, 0, 0
>>>
>>> This is weird. Either you were lucky, your embedded devices aren't able to
>>> send back-to-back at that rate specifically, or the situation regarding
>>> load and latency spikes changed somehow. The results don't make sense to
>>> me.
>>
>> Well, I guess this will change if I would run more than 3 times, but as
>> overruns already occured at 250kBit/s there _is_ still a problem in rx-fifo,
>> independently from 1MBit/s drops due to heavy load.
> 
> Well, I now think that rx-fifo was never intended to improve the driver
> performance (correct me if I'm wrong, Marc), but only to build a common
> subsystem around the same concept that seems to be re-invented in at91_can,
> flexcan and ti_hecc. It does fix the lockup-bug in at91_can though.

Exactly. It's supposed to abstract the make-a-fifo code from the
hardware and move it into the CAN driver core.

Marc

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