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

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Message-ID: <4F848F88.7060009@suse.cz>
Date:	Tue, 10 Apr 2012 21:52:40 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
CC:	Chris Wilson <chris@...is-wilson.co.uk>,
	Jiri Slaby <jirislaby@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	dri-devel@...ts.freedesktop.org, daniel@...ll.ch
Subject: Re: i915_driver_irq_handler: irq 42: nobody cared

On 04/10/2012 08:34 PM, 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?

Yes.

> You could try masking hotplug interrupts altogether.

This doesn't help:
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -2049,7 +2051,7 @@ static int i915_driver_irq_postinstall(struct
drm_device *dev)
        I915_WRITE(IER, enable_mask);
        POSTING_READ(IER);

-       if (I915_HAS_HOTPLUG(dev)) {
+       if (0 && I915_HAS_HOTPLUG(dev)) {
                u32 hotplug_en = I915_READ(PORT_HOTPLUG_EN);

                /* Note HDMI and DP share bits */


> Also, just to sanity check things, can you look at the output of
> "lspci -s 02.0 -vvv -xxx" and see if the "INTx" field is + or -?
> If it's +, then the interrupt is definitely coming from an un-acked
> IRQ source on the gfx device.  If it's INTx-, it means something in
> one of the upper MSI layers isn't getting handled right.

Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-

I tried 3.2 and 3.3. Although the spurious interrupts were always
there, they occurred with frequency lower by a magnitude (15 vs. 300
after X starts). So I bisected that and it lead to a commit which
fixes bad tiling for me:
http://cgit.freedesktop.org/~ickle/linux-2.6/commit/?h=for-jiri&id=79710e6ccabdac80c65cd13b944695ecc3e42a9d

thanks,
-- 
js
suse labs


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