From: David Gibson <david@gibson.dropbear.id.au>
To: Valentine Barshak <vbarshak@ru.mvista.com>
Cc: linuxppc-dev@ozlabs.org
Subject: Re: [ PATCH ] PowerPC cascade UIC IRQ handler fix.
Date: Thu, 2 Aug 2007 13:48:48 +1000 [thread overview]
Message-ID: <20070802034848.GA837@localhost.localdomain> (raw)
In-Reply-To: <20070730163517.GA10087@ru.mvista.com>
On Mon, Jul 30, 2007 at 08:35:17PM +0400, Valentine Barshak wrote:
> PPC44x cascade UIC irq handler fix.
>
> According to PPC44x UM, if an interrupt is configured as level-sensitive,
> and a clear is attempted on the UIC_SR, the UIC_SR field is not
> cleared if the incoming interrupt signal is at the asserted polarity.
> This causes us to enter a cascade handler twice, since we first ack
> parent UIC interrupt and ack child UIC one after that.
> The patch checks child UIC msr value and returns IRQ_HANDLED
> if there're no pending interrupts. Otherwise we get a kernel panic
> with a "Fatal exception in interrupt" (illegal vector).
> The patch also fixes status flags.
>
> Signed-off-by: Valentine Barshak <vbarshak@ru.mvista.com>
Hrm... This doesn't seem like the right fix to me. Instead, I think
the cascaded IRQ handler should ack the interrupt on the child first.
I'm a little surprised it doesn't at the moment.
> ---
>
> --- linux.orig/arch/powerpc/sysdev/uic.c 2007-07-27 20:37:11.000000000 +0400
> +++ linux/arch/powerpc/sysdev/uic.c 2007-07-30 20:26:48.000000000 +0400
> @@ -142,7 +142,7 @@
>
> desc->status &= ~(IRQ_TYPE_SENSE_MASK | IRQ_LEVEL);
> desc->status |= flow_type & IRQ_TYPE_SENSE_MASK;
> - if (trigger)
> + if (!trigger)
> desc->status |= IRQ_LEVEL;
>
> spin_unlock_irqrestore(&uic->lock, flags);
> @@ -207,6 +207,9 @@
> int subvirq;
>
> msr = mfdcr(uic->dcrbase + UIC_MSR);
> + if (!msr)
> + return IRQ_HANDLED;
> +
> src = 32 - ffs(msr);
>
> subvirq = irq_linear_revmap(uic->irqhost, src);
> _______________________________________________
> Linuxppc-dev mailing list
> Linuxppc-dev@ozlabs.org
> https://ozlabs.org/mailman/listinfo/linuxppc-dev
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
next prev parent reply other threads:[~2007-08-02 3:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-30 16:35 [ PATCH ] PowerPC cascade UIC IRQ handler fix Valentine Barshak
2007-08-02 3:48 ` David Gibson [this message]
2007-08-02 20:08 ` Josh Boyer
2007-08-03 11:09 ` Valentine Barshak
2007-08-03 1:18 ` Benjamin Herrenschmidt
2007-08-03 4:57 ` David Gibson
2007-08-03 6:23 ` David Gibson
2007-08-13 1:08 ` David Gibson
2007-08-13 12:31 ` Valentine Barshak
2007-08-14 1:35 ` David Gibson
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