linux-kernel - Re: [PATCH v2 5/6] Sysace: Move IRQ handler registration to occur after FSM is initialized

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Message-Id: <1191304521.6310.94.camel@pasglop>
Date:	Tue, 02 Oct 2007 15:55:21 +1000
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	paulus@...ba.org, axboe@...nel.dk
Subject: Re: [PATCH v2 5/6] Sysace: Move IRQ handler registration to occur
	after FSM is initialized


On Sun, 2007-09-30 at 16:57 -0600, Grant Likely wrote:
>         val |= ACE_CTRL_DATABUFRDYIRQ | ACE_CTRL_ERRORIRQ;
>         ace_out(ace, ACE_CTRL, val);
>  
> +       /* Now we can hook up the irq handler */
> +       if (ace->irq != NO_IRQ) {
> +               rc = request_irq(ace->irq, ace_interrupt, 0,
> "systemace", ace);
> +               if (rc) {
> +                       /* Failure - fall back to polled mode */
> +                       dev_err(ace->dev, "request_irq failed\n");
> +                       ace->irq = NO_IRQ;
> +               }
> +       }
> +

I don't know the HW but from the above, it looks like you enable
interrupt emission on the HW before you register the handler, which is
wrong. You should make sure on the contrary that IRQs on the HW are
disabled until after you have registered a handler.

Only really a problem if you have shared interrupts but still...

Ben.

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