netdev - Re: [PATCH] flexcan: Acknowledge all interrupt sources in the IRQ handler

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Date:	Fri, 09 Dec 2011 15:35:02 +0100
From:	Wolfgang Grandegger <wg@...ndegger.com>
To:	Lothar Waßmann <LW@...O-electronics.de>
CC:	Marc Kleine-Budde <mkl@...gutronix.de>, linux-can@...r.kernel.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] flexcan: Acknowledge all interrupt sources in the IRQ
 handler

On 12/09/2011 02:59 PM, Lothar Waßmann wrote:
> Hi,
> 
> Marc Kleine-Budde writes:
>> On 12/09/2011 02:47 PM, Lothar Waßmann wrote:
>>> Otherwise the handler will get stuck in an endless IRQ loop when an
>>> interrupt condition occurs that is not being acked (e.g. TWRN)
>>
>> On which CPU do you have this problem?
>>
> on i.MX28.

Yes, it is definitely needed on i.MX28 and I already have it in my
series. See:

https://gitorious.org/~wgrandegger/linux-can/wg-linux-can-next/commit/8ad94fa0dd7f7728824fa8fd4479390ac3f189c7

BTW: at similar patch was already sent by Reuben Dowle.

>> Seems that mx25/35 behave a bit different than mx28. But I had no time
>> to dig into this, yet. BTW Wolfgang is just reworking error handling,
>> can you please test his patches he recently posted on linux-can.
>>
> The ESR of i.MX25 is completely identical to the i.MX28.
> You should be able to reproduce the problem when trying to send a
> message to a CAN interface with the transceiver disabled.
> You will get a BIT0_ERR and the TWRN bit will be asserted and never
> cleared leading to an endless interrupt loop.

If you are right, the code was never working on i.MX25/35... which I doubt.

Wolfgang.
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