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

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Date:	Sat, 28 Jun 2008 05:09:28 +0400
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-ide@...r.kernel.org,
	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Sergei Shtylyov <sshtylyov@...mvista.com>,
	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 04:54:36AM +0400, 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.
> 
> 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.
> 
> This patch fixes following issue:
> 
> ALI15X3: IDE controller (0x10b9:0x5229 rev 0xc8) at  PCI slot 0001:03:1f.0
> ALI15X3: 100% native mode on irq 18
> ide0: BM-DMA at 0x1120-0x1127, BIOS settings: hda:PIO, hdb:PIO
> ide1: BM-DMA at 0x1128-0x112f, BIOS settings: hdc:PIO, hdd:PIO
> hda: Optiarc DVD RW AD-7190A, ATAPI CD/DVD-ROM drive
> hda: UDMA/66 mode selected
> ide0 at 0x1100-0x1107,0x110a on irq 18
> ide-cd: cmd 0x5a timed out
> hda: lost interrupt
> hda: ATAPI 12X DVD-ROM DVD-R-RAM CD-R/RW drive, 2048kB Cache
> Uniform CD-ROM driver Revision: 3.20
> ide-cd: cmd 0x3 timed out
> hda: lost interrupt
> ide-cd: cmd 0x3 timed out
> hda: lost interrupt
> ...
> 
> It would be great to re-configure the ULi bridge or ULi IDE controller
> to behave sanely, but no one knows how or if this is possible at all
> (no available specifications).

Btw, thanks to Jeff Garzik for mentioning this link:

http://gkernel.sourceforge.net/specs/

Though, from a brief glance there is nothing much useful for this ULi
chip. The only thing I gathered is that IDE controller does not provide
any means of configuring its IRQs behaviour, so it is indeed ULi's bridge
problems. It doesn't change anything, just another data point...

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