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From: Michael Walle <michael@walle.cc>
To: marcelo.jimenez@gmail.com
Cc: achant@google.com, brgl@bgdev.pl, edmondchung@google.com,
	geert@linux-m68k.org, linus.walleij@linaro.org,
	linux-gpio@vger.kernel.org, regressions@lists.linux.dev,
	sfr@canb.auug.org.au, stable@vger.kernel.org,
	tanzilli@acmesystems.it, treding@nvidia.com, vidyas@nvidia.com,
	willmcvicker@google.com,
	Horatiu Vultur <horatiu.vultur@microchip.com>,
	Lars Povlsen <lars.povlsen@microchip.com>,
	Michael Walle <michael@walle.cc>
Subject: Re: [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c)
Date: Mon, 14 Mar 2022 16:55:09 +0100	[thread overview]
Message-ID: <20220314155509.552218-1-michael@walle.cc> (raw)
In-Reply-To: <20211217153555.9413-1-marcelo.jimenez@gmail.com>

Hi,

> Some GPIO lines have stopped working after the patch
> commit 2ab73c6d8323f ("gpio: Support GPIO controllers without pin-ranges")
> 
> And this has supposedly been fixed in the following patches
> commit 89ad556b7f96a ("gpio: Avoid using pin ranges with !PINCTRL")
> commit 6dbbf84603961 ("gpiolib: Don't free if pin ranges are not defined")
> 
> But an erratic behavior where some GPIO lines work while others do not work
> has been introduced.
> 
> This patch reverts those changes so that the sysfs-gpio interface works
> properly again.
> 
> Signed-off-by: Marcelo Roberto Jimenez <marcelo.jimenez@gmail.com>

This breaks the pinctrl-microchip-sgpio driver as far as I can see.

I tried to debug it and this is what I have discovered so far:
 (1) the sgpio driver will use the gpio_stub_drv for its child nodes.
     Looks like a workaround, see [1].
 (2) these will have an empty gpio range
 (3) with the changes of this patch, pinctrl_gpio_request() will now
     be called and will fail with -EPROBE_DEFER.

I'm not exactly sure what to do here. Saravana Kannan once suggested
to use devm_of_platform_populate() to probe the child nodes [2]. But
I haven't found any other driver doing that.

Also, I'm not sure if there are any other other driver which get
broken by this. I.e. ones falling into the gpio_stub_drv category.

[1] https://lore.kernel.org/lkml/20210122193600.1415639-1-saravanak@google.com/
[2] https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/

-michael

NB. this patch doesn't contain a Fixes tag. Was this on purpose?

  parent reply	other threads:[~2022-03-14 16:02 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-17 15:35 [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c) Marcelo Roberto Jimenez
2021-12-18  6:28 ` Thorsten Leemhuis
2021-12-20 14:57   ` Bartosz Golaszewski
2021-12-20 15:14     ` Geert Uytterhoeven
2021-12-20 19:24       ` Will McVicker
2021-12-20 20:41         ` Marcelo Roberto Jimenez
2021-12-20 20:41       ` Marcelo Roberto Jimenez
2021-12-20 20:41     ` Marcelo Roberto Jimenez
2022-01-10  7:02       ` Thorsten Leemhuis
2022-01-12  0:09         ` Marcelo Roberto Jimenez
2022-02-08 12:24           ` Thorsten Leemhuis
2022-02-17 19:11           ` Thierry Reding
2022-05-30 13:43   ` [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c) #forregzbot Thorsten Leemhuis
2022-02-11  0:02 ` [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c) Linus Walleij
2022-02-11 22:36   ` Marcelo Roberto Jimenez
2022-02-12 16:54     ` Linus Walleij
2022-02-13 23:23       ` Marcelo Roberto Jimenez
2022-02-15 21:56         ` Linus Walleij
2022-02-16 14:40           ` Bartosz Golaszewski
2022-03-04  7:13             ` Thorsten Leemhuis
2022-03-07  9:58               ` Bartosz Golaszewski
2022-03-07 10:12                 ` Thorsten Leemhuis
2022-03-15  5:18                   ` [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c) #forregzbot Thorsten Leemhuis
2022-05-20  9:12             ` [PATCH] gpio: Revert regression in sysfs-gpio (gpiolib.c) Thorsten Leemhuis
2022-05-20 17:28               ` Marcelo Roberto Jimenez
2022-03-14 15:55 ` Michael Walle [this message]
2022-03-15 15:32   ` Bartosz Golaszewski
2022-03-15 15:45     ` Michael Walle
2022-03-17  8:37       ` Andy Shevchenko
2022-03-17  8:48         ` Michael Walle

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