linux-kernel - Re: [PATCH] drm/nouveau: Remove interrupt handler around suspend/resume

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Date:	Thu, 28 Apr 2011 15:54:28 +1000
From:	Dave Airlie <airlied@...hat.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/nouveau: Remove interrupt handler around
 suspend/resume

On Wed, 2011-04-27 at 23:20 -0600, Alex Williamson wrote:
> We're often using a shared interrupt line for nouveau, so we have
> to be prepared that it could be called at any point in time.  If
> we've suspended the device via vga switcheroo and get a stray
> interrupt on the line from another device, we'll read back -1 from
> the device and head down all sorts of strange paths, most of which
> eventually lock the system.
> 
> On my system (Asus UL30VT) the interrupt line is shared with USB.
> Attempting to disable the USB bluetooth device seems to trigger
> a stray interrupt that ends up in nv04_fifo_isr() where we
> eventually hit the "PFIFO still angry after 100 spins, halt",
> which kills the system.
> 
> Using free_irq/request_irq around the suspend seems to be a
> reliable fix.  Attempting to flag the device state in
> nouvea_irq_handler(), similar to the intel_lid_notify() fix
> is too racy since we can power off the device as an interrupt
> is being processed.

The actual solution is to check if we read back all Fs and return from
the irq handler. Robust irq handlers are generally considered a good
idea esp around race conditions at suspend/resume time.

Dave.


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