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

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Date:	Thu, 30 Oct 2014 13:56:46 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	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

On Mon, Oct 27, 2014 at 01:58:19PM +0100, 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:
> 
> 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.

I tried to fix it in a proper way, but it seems people were uneasy with
how invasive the change was. At some point I lost interest. People ended
up merging something that was similar, but side-stepped the issue of
propagating error codes all the way up by introducing a new API and in
case of of_irq_parse_one() failing doing an additional check to see if
the reason was the missing IRQ domain.

See:

	9ec36cafe43b of/irq: do irq resolution in platform_get_irq

I suspect a similar thing could be done for I2C.

Thierry

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