linux-kernel - Re: [PATCH v2 -rt] ide: workaround buggy hardware issues with preemptable hardirqs

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Date:	Sat, 28 Jun 2008 15:52:02 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	avorontsov@...mvista.com
Cc:	Ingo Molnar <mingo@...e.hu>, linux-ide@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Walker <dwalker@...sta.com>
Subject: Re: [PATCH v2 -rt] ide: workaround buggy hardware issues with	preemptable
 hardirqs

Hello.

Anton Vorontsov wrote:
>>> But some hardware (namely ULi M5228 in the ULi M1575 "Super South Brige")
>>> behaves in a strange way: it asserts interrupts as edge sensitive. And
>>> because preemptable IRQ handler disables PIC's interrupt, PIC will likely
>>> miss it.
>>>   
>>>       
>>   Unmasking an IRQ should re-enable an edge detector in a PIC (or that  
>> detector should even be independent from mask).
>>     
> Should? Hm.. well, I can easily check it. Will just program the MPIC IRQ
> to edge sensitive, and see if it fixes the problem (not sure if I already
> tried this, I think I did try).
>   

   That will not help if edge detector is not active for masked out IRQs 
(that's how i8259 behaves, IIRC) *and* you're getting the short IRQ 
"pulses" but should help if IRQ is generated normally -- though in this 
case the level trigger mode (with the same polarity) should work as well...

MBR, Sergei


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