linux-kernel - Re: [Linux-zigbee-devel] [PATCH 2/2] mrf24j40: Keep the interrupt line enabled

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Message-ID: <CAO+c-UWi5UH-ZN5G0JiJCrCrScaYprKT7jLpFH0wEJecgoHgig@mail.gmail.com>
Date:	Thu, 16 May 2013 23:34:11 +0200
From:	David Hauweele <david@...weele.net>
To:	Alan Ott <alan@...nal11.us>
Cc:	Alexander Smirnov <alex.bluesman.smirnov@...il.com>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	linux-zigbee-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [Linux-zigbee-devel] [PATCH 2/2] mrf24j40: Keep the interrupt
 line enabled

I have seen the interrupt line going low forever with heavy traffic.

The at86rf230 driver has two isr, one for edge-triggered and another
for level-triggered interrupt. The latter uses
disable_irq_nosync/enable_irq which makes sense for level-triggered
interrupt. Otherwise the interrupt would be triggered again and again
until the scheduled work read the status register.

However I don't see the use of disable_irq/enable_irq with an
edge-triggered interrupt. Perhaps I'm missing something. Though I
don't see any harm using it anyway. As you said the interrupt should
be delayed until enable_irq() is called. In particular when
CONFIG_HARDIRQS_SW_RESEND is set.

David

2013/5/14 Alan Ott <alan@...nal11.us>:
> On 5/9/13 11:19 AM, David Hauweele wrote:
>>
>> Disabling the interrupt line could miss an IRQ and leave the line into a
>> low state hence locking the driver.
>>
>
> Have you observed this? My understanding is that the interrupt won't be lost
> but instead delayed until enable_irq() is called.
>
> I got this pattern from the other 802.15.4 drivers. Perhaps my understanding
> is wrong.
>
>
>
>> Signed-off-by: David Hauweele <david@...weele.net>
>> ---
>>   drivers/net/ieee802154/mrf24j40.c |    7 +------
>>   1 file changed, 1 insertion(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/ieee802154/mrf24j40.c
>> b/drivers/net/ieee802154/mrf24j40.c
>> index 1e3ddf3..6ef32f7 100644
>> --- a/drivers/net/ieee802154/mrf24j40.c
>> +++ b/drivers/net/ieee802154/mrf24j40.c
>> @@ -603,8 +603,6 @@ static irqreturn_t mrf24j40_isr(int irq, void *data)
>>   {
>>         struct mrf24j40 *devrec = data;
>>
>> -       disable_irq_nosync(irq);
>> -
>>         schedule_work(&devrec->irqwork);
>>
>>         return IRQ_HANDLED;
>> @@ -619,7 +617,7 @@ static void mrf24j40_isrwork(struct work_struct *work)
>>         /* Read the interrupt status */
>>         ret = read_short_reg(devrec, REG_INTSTAT, &intstat);
>>         if (ret)
>> -               goto out;
>> +               return;
>>
>>         /* Check for TX complete */
>>         if (intstat & 0x1)
>> @@ -628,9 +626,6 @@ static void mrf24j40_isrwork(struct work_struct *work)
>>         /* Check for Rx */
>>         if (intstat & 0x8)
>>                 schedule_work(&devrec->rxwork);
>> -
>> -out:
>> -       enable_irq(devrec->spi->irq);
>>   }
>>
>>   static void mrf24j40_rxwork(struct work_struct *work)
>>
>
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