linux-kernel - Re: I2C OF IRQ parsing issue due to probe ordering

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Date:	Thu, 30 Oct 2014 15:12:43 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: I2C OF IRQ parsing issue due to probe ordering

Hi Thierry,

On Thursday 30 October 2014 14:02:09 Thierry Reding wrote:
> On Thu, Oct 30, 2014 at 02:53:42PM +0200, Laurent Pinchart wrote:
> > On Monday 27 October 2014 13:58:19 Wolfram Sang wrote:
> > > > The i2c@...20000 node is probed before the gpio@...51000 node. The
> > > > of_i2c_register_devices() function tries to register all children,
> > > > including hdmi@39. It tries to parse and map the I2C client IRQ by
> > > > calling irq_of_parse_and_map(), which returns 0 as the interrupt
> > > > controller isn't probed yet. The adv7511 driver later probes the
> > > > hdmi@39
> > > > device and gets client->irq set to 0.
> > > 
> > > I've got this strange feeling of deja vu... Ah, here: Thierry Reding
> > 
> > > tackled this problem a year ago. His series:
> > Thanks for the pointer.
> > 
> > > https://lkml.org/lkml/2013/9/16/111 (of/irq: Defer interrupt reference
> > > resolution)
> > > 
> > > He did a V2 (which never made it to the i2c list). Seems like the first
> > > two patches made it and the rest got stalled without discussion?
> > > 
> > > https://lkml.org/lkml/2013/9/18/216
> > > 
> > > Adding Thierry to the queue. Maybe he can bring some light to what
> > > happened to his series.
> > 
> > That's exactly what I need :-) Thierry, do you plan to respin the series ?
> 
> Not really. Like I said in my reply to Wolfram, a different set of
> patches was merged subsequently to solve this issue for platform
> devices, which makes my patchset mostly obsolete. But I think the
> solution that you proposed would work well if you do:
> 
> -		int irq = irq_of_parse_and_map(dev->of_node, 0);
> +		int irq = of_irq_get(dev->of_node, 0);
> 
> And then changing irq_create_of_mapping() should no longer be necessary.

It looks like it would work, yes. I'll test it and will resubmit my patch.

> I still think it's kind of lame to handle -EPROBE_DEFER specially as was
> done in of_irq_get(), but given how worried people were about the more
> invasive changes needed to propagate the correct error code all the way
> up it seems like that's as good as it's going to get.

-- 
Regards,

Laurent Pinchart

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