linux-kernel - Re: i915_driver_irq_handler: irq 42: nobody cared

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Message-ID: <20120411090318.121a6d6b@jbarnes-desktop>
Date:	Wed, 11 Apr 2012 09:03:18 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	Michel Dänzer <michel@...nzer.net>
Cc:	Jiri Slaby <jslaby@...e.cz>, LKML <linux-kernel@...r.kernel.org>,
	Jiri Slaby <jirislaby@...il.com>,
	dri-devel@...ts.freedesktop.org
Subject: Re: i915_driver_irq_handler: irq 42: nobody cared

On Wed, 11 Apr 2012 08:29:22 +0200
Michel Dänzer <michel@...nzer.net> wrote:

> On Die, 2012-04-10 at 11:34 -0700, Jesse Barnes wrote: 
> > On Tue, 10 Apr 2012 20:11:29 +0200
> > Jiri Slaby <jslaby@...e.cz> wrote:
> > 
> > > On 04/10/2012 06:26 PM, Jesse Barnes wrote:
> > > > So port hotplug is always reporting that port C has a hotplug
> > > > interrupt though...  If you write 0x3 back to it does the interrupt
> > > > stop?
> > > 
> > > I'm not sure I got it right. This doesn't help:
> > > --- a/drivers/gpu/drm/i915/i915_irq.c
> > > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > > @@ -1416,6 +1416,17 @@ static irqreturn_t
> > > i915_driver_irq_handler(DRM_IRQ_ARGS)
> > >                 iir = new_iir;
> > >         }
> > > 
> > > +       if (ret == IRQ_NONE) {
> > > +               u32 hp = I915_READ(PORT_HOTPLUG_STAT);
> > > +               if (hp) {
> > > +                       I915_WRITE(PORT_HOTPLUG_STAT, hp);
> > > +                       I915_READ(PORT_HOTPLUG_STAT);
> > > +               }
> > > +
> > > +               if (printk_ratelimit())
> > > +                       printk(KERN_DEBUG "%s: %.8x\n", __func__, hp);
> > > +
> > > +       }
> > > 
> > >         return ret;
> > >  }
> > 
> > Yeah that looks right, you still get 0x300?
> 
> You said 'If you write 0x3 back' above, but this code writes 0x300.
> Which is right?

0x300 is right, the bits are status bits with write 1 to clear
semantics.  But it looks like this one is just stuck high (probably
because port C isn't actually wired up fully).

-- 
Jesse Barnes, Intel Open Source Technology Center

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