netdev - Re: [PATCH] net: davinci_emac: Move call of devm_request_irq to emac_dev

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Date:	Tue, 4 Mar 2014 09:53:59 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Prabhakar Lad <prabhakar.csengg@...il.com>
Cc:	Christian Riesch <christian.riesch@...cron.at>,
	netdev <netdev@...r.kernel.org>, Jon Ringle <jon@...gle.org>,
	dlos <davinci-linux-open-source@...ux.davincidsp.com>,
	stable <stable@...r.kernel.org>
Subject: Re: [PATCH] net: davinci_emac: Move call of devm_request_irq to emac_dev_open

2014-03-04 9:30 GMT-08:00 Prabhakar Lad <prabhakar.csengg@...il.com>:
> Hi Christian,
>
> Thanks for the patch.
>
>
> On Tue, Mar 4, 2014 at 7:37 PM, Christian Riesch
> <christian.riesch@...cron.at> wrote:
>> In commit 6892b41d9701283085b655c6086fb57a5d63fa47
>>
>> Author: Lad, Prabhakar <prabhakar.csengg@...il.com>
>> Date:   Tue Jun 25 21:24:51 2013 +0530
>> net: davinci: emac: Convert to devm_* api
>>
>> the call of request_irq is replaced by devm_request_irq and the call
>> of free_irq is removed. But since interrupts are requested in
>> emac_dev_open, doing ifconfig up/down on the board requests the
>> interrupts again each time, causing devm_request_irq to fail.
>>
>> This patch moves the interrupt requests to emac_dev_open and thus
>> fixes this regression.
>>
>> Reported-by: Jon Ringle <jon@...gle.org>
>> Signed-off-by: Christian Riesch <christian.riesch@...cron.at>
>> Cc: Lad, Prabhakar <prabhakar.csengg@...il.com>
>> Cc: <stable@...r.kernel.org>
>
> This patch fixes issue pointed at
> http://comments.gmane.org/gmane.linux.davinci/28135
> tested on Logic PD.
>
>  Reported-and-tested-by: Lad, Prabhakar <prabhakar.csengg@...il.com>
>
> Assuming you will respin the patch fixing the header.
>> ---
>>
>> Hi,
>> This is an attempt to fix the bug discussed in
>> https://lkml.org/lkml/2014/3/4/218
>>
>> Since I am not really familiar with interrupts I am not sure if this is the right way to
>> do it. I am looking forward to your comments.
>>
> Looks OK.

I think a plain revert of Prabhakar patch would bring us in an "usual"
situation where the drivers's ndo_open():

- masks all interrupts bits at the Ethernet MAC level
- calls request_irq()
- unmask relevant interrupts bits at the Ethernet Mac level

just in case some uncontrolled interrupt bit triggers an interrupt
while the interface is down for instance...

On a wider note, it would be good to get some tool to notify people
that attempting to replace devm_request_irq() in a network driver's
ndo_open() function is not going to produce the expected results as
the two are not strictly identical.
-- 
Florian
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