netdev - Re: [PATCH] can: flexcan: fix irq flooding by clearing all interrupt sources

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Date:	Tue, 13 Dec 2011 13:53:04 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	Wolfgang Grandegger <wg@...ndegger.com>
CC:	netdev@...r.kernel.org, linux-can@...r.kernel.org,
	Reuben Dowle <Reuben.Dowle@...ico.com>,
	Lothar Waßmann <LW@...O-electronics.de>
Subject: Re: [PATCH] can: flexcan: fix irq flooding by clearing all interrupt
 sources

On 12/13/2011 01:13 PM, Wolfgang Grandegger wrote:
> On 12/12/2011 04:44 PM, Wolfgang Grandegger wrote:
>> On 12/12/2011 04:31 PM, Marc Kleine-Budde wrote:
>>> On 12/12/2011 04:09 PM, Wolfgang Grandegger wrote:
>>>> As pointed out by Reuben Dowle and Lothar Waßmann, the TWRN_INT,
>>>> RWRN_INT, BOFF_INT interrupt sources need to be cleared as well
>>>> to avoid interrupt flooding, at least for the Flexcan on i.MX28
>>>> SOCs. Furthermore, the interrupts are only cleared, if really one
>>>> of those interrupt sources are pending (which is not the case for
>>>> rx and tx done).
>>>>
>>>> CC: Reuben Dowle <Reuben.Dowle@...ico.com>
>>>> CC: Lothar Waßmann <LW@...O-electronics.de>
>>>> Signed-off-by: Wolfgang Grandegger <wg@...ndegger.com>
>>>
>>> Have you tested on mx25/mx35, does it have any negative side effects?
>>> My schedule is full until Friday, sorry cannot test here.
>>
>> Not yet. But it's not critical. Only the pending interrupt flags are
>> cleared. Maybe somebody else out there could do some testing... before I
>> get hold of a MX35PDK board.
> 
> I got my MX35PDK board working and can confirm, that the patch works on
> a i.mx35 as well. My testing also confirms, that the ESR TWRN_INT,
> RWRN_INT, FLEXCAN_ESR_BOFF_INT do not function as documented. These
> flags do show up once, together with ERR_INT, and then, after clearing,
> never again. Obviously a bug in the Flexcan logic. From the feedback we
> can say, that only the i.MX28 does behave differently (==correctly). All
> other seem to work with the current code:
> 
>  Flexcan on
>  - i.mx25
>  - i.mx35
>  - i.mx53
>  - P1010/P1020

I'm adding the patch to linux-can. I think this is a stable candidate
for v2.6.39 and newer (mx28 suport was added in 2.6.39).

Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
Vertretung West/Dortmund          | Fax:   +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686  | http://www.pengutronix.de   |


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