linux-kernel - Re: [PATCH v2] Staging: Correct tsi-148 VME interrupt free routine

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Date:	Thu, 06 Aug 2009 08:20:52 +0100
From:	Martyn Welch <martyn.welch@...anuc.com>
To:	Jiri Slaby <jirislaby@...il.com>
CC:	gregkh@...e.de, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org
Subject: Re: [PATCH v2] Staging: Correct tsi-148 VME interrupt free routine

Jiri Slaby wrote:
> On 08/05/2009 06:38 PM, Martyn Welch wrote:
>   
>>  	if (tsi148_bridge->irq[level - 1].count == 0) {
>> -		tmp = ioread32be(tsi148_bridge->base + TSI148_LCSR_INTEO);
>> -		tmp &= ~TSI148_LCSR_INTEO_IRQEO[level - 1];
>> -		iowrite32be(tmp, tsi148_bridge->base + TSI148_LCSR_INTEO);
>> -
>>  		tmp = ioread32be(tsi148_bridge->base + TSI148_LCSR_INTEN);
>>  		tmp &= ~TSI148_LCSR_INTEN_IRQEN[level - 1];
>>  		iowrite32be(tmp, tsi148_bridge->base + TSI148_LCSR_INTEN);
>> +
>> +		tmp = ioread32be(tsi148_bridge->base + TSI148_LCSR_INTEO);
>> +		tmp &= ~TSI148_LCSR_INTEO_IRQEO[level - 1];
>> +		iowrite32be(tmp, tsi148_bridge->base + TSI148_LCSR_INTEO);
>>     
>
> I have no idea what the registers do and I suppose it's behind some PCI
> bridge anywhere. If it is not true, ignore the further.
>
> Is it OK that the second write to INTEO doesn't reach the device before
> you set func to NULL? I mean, is it enough to prevent the interrupt
> raising only by twiddling INTEN? Otherwise you need to put some read
> right here to push non-completed writes on bridges (flush posted
> writes). (I mentioned this in the former mail too.)
>   

Yes, this is fine:

TSI148_LCSR_INTEN = Interrupt Enable
TSI148_LCSR_INTEO = Interrupt Output Enable

If an interrupt source is completely disabled, it doesn't matter whether or not it is stopped from generating a PCI interrupt.

Martyn

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Martyn Welch MEng MPhil MIET (Principal Software Engineer)   T:+44(0)1327322748
GE Fanuc Intelligent Platforms Ltd,        |Registered in England and Wales
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