From: Peter Zijlstra <peterz@infradead.org>
To: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Alexandre Courbot <gnurou@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
linux-gpio <linux-gpio@vger.kernel.org>
Subject: Re: lockdep: incorrect deadlock warning with two GPIO expanders
Date: Mon, 12 Sep 2016 17:33:56 +0200 [thread overview]
Message-ID: <20160912153356.GD10121@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <CAMpxmJW5WNF2zE+fjmpDxubAYA_A67iQhNGTvSAL-MD-6dFTCw@mail.gmail.com>
On Mon, Sep 12, 2016 at 05:16:14PM +0200, Bartosz Golaszewski wrote:
> >> - - - - -
> >> ------- --------- Bus segment 1 | |
> >> | | | |--------------- Devices
> >> | | SCL/SDA | | | |
> >> | Linux |-----------| I2C MUX | - - - - -
> >> | | | | | Bus segment 2
> >> | | | | |-------------------
> >> ------- | --------- |
> >> | | - - - - -
> >> ------------ | MUX GPIO | |
> >> | | | Devices
> >> | GPIO | | | |
> >> | Expander 1 |---- - - - - -
> >> | | |
> >> ------------ | SCL/SDA
> >> |
> >> ------------
> >> | |
> >> | GPIO |
> >> | Expander 2 |
> >> | |
> >> ------------
> > The tricky part, and here I have absolutely no clue what so ever, is
> > being able to tell at pca953x_probe() time that this is so.
> >
>
> AFAIK there is no clean way to tell that a GPIO is used by an I2C
> multiplexer at probe time. Linus, Alexandre could you confirm?
You cannot inspect the device tree while probing?
> It uses the fact that the two expanders we have are of different type
> (pca9534 and pca9535). The id pointer points to per-chip device info
> residing in .data which makes it suitable for mutex key.
>
> I don't think such hack is suitable for mainline though.
Right, that works by accident rather than anything else :-)
next prev parent reply other threads:[~2016-09-12 15:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-12 11:51 lockdep: incorrect deadlock warning with two GPIO expanders Bartosz Golaszewski
2016-09-12 12:09 ` Peter Zijlstra
2016-09-12 15:16 ` Bartosz Golaszewski
2016-09-12 15:33 ` Peter Zijlstra [this message]
2016-09-13 12:29 ` Linus Walleij
2016-09-15 7:51 ` Peter Zijlstra
2016-09-15 12:41 ` Linus Walleij
2016-09-15 13:20 ` Bartosz Golaszewski
2016-09-15 13:39 ` Peter Zijlstra
2016-09-15 14:08 ` Bartosz Golaszewski
2016-09-15 14:38 ` Peter Zijlstra
2016-09-15 15:23 ` Bartosz Golaszewski
2016-09-16 10:56 ` Peter Zijlstra
2016-09-16 11:14 ` Bartosz Golaszewski
2016-09-16 12:00 ` Bartosz Golaszewski
2016-09-16 14:21 ` Bartosz Golaszewski
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