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

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Date:	Sat, 28 Jun 2008 15:31:26 +0400
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Sergei Shtylyov <sshtylyov@...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

On Sat, Jun 28, 2008 at 02:30:36PM +0400, Sergei Shtylyov wrote:
> Hello.
>
> Anton Vorontsov wrote:
>> IDE interrupt handler relies on the fact that, if necessary, hardirqs
>> will re-trigger on ISR exit. The assumption is valid for level sensitive
>> interrupts.
>>   
>
>   It's valid for both edge and level triggered interrupts.

I think this is depends on PIC, whether it can or can not detect masked
edge interrupts...

>> 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).

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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