linux-kernel - Re: [PATCH v1 1/1] gpiolib: Read "gpio-line-names" from a firmware node

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Date:   Sat, 10 Apr 2021 11:06:55 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Marek Vasut <marex@...x.de>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Roman Guskov <rguskov@...electronics.com>
Subject: Re: [PATCH v1 1/1] gpiolib: Read "gpio-line-names" from a firmware node

On Sat, Apr 10, 2021 at 2:46 AM Marek Vasut <marex@...x.de> wrote:
>
> On 3/15/21 6:04 PM, Andy Shevchenko wrote:
> > On Mon, Mar 15, 2021 at 6:49 PM Bartosz Golaszewski
> > <bgolaszewski@...libre.com> wrote:
> >>
> >> On Mon, Mar 15, 2021 at 3:34 PM Andy Shevchenko
> >> <andriy.shevchenko@...ux.intel.com> wrote:
> >>>
> >>> On Mon, Mar 15, 2021 at 03:04:37PM +0100, Bartosz Golaszewski wrote:
> >>>> On Mon, Mar 15, 2021 at 1:50 PM Andy Shevchenko
> >>>> <andriy.shevchenko@...ux.intel.com> wrote:
> >>>>>
> >>>>> On Mon, Mar 15, 2021 at 12:16:26PM +0200, Andy Shevchenko wrote:
> >>>>>> On Mon, Mar 15, 2021 at 10:01:47AM +0100, Bartosz Golaszewski wrote:
> >>>>>>> On Fri, Mar 5, 2021 at 1:03 PM Andy Shevchenko
> >>>>>>> <andriy.shevchenko@...ux.intel.com> wrote:
> >>>>>>
> >>>>>>> Unfortunately while this may fix the particular use-case on STM32, it
> >>>>>>> breaks all other users as the 'gpio-line-names' property doesn't live
> >>>>>>> on dev_fwnode(&gdev->dev) but on dev_fwnode(chip->parent).
> >>>>>>>
> >>>>>>> How about we first look for this property on the latter and only if
> >>>>>>> it's not present descend down to the former fwnode?
> >>>>>>
> >>>>>> Oops, I have tested on x86 and it worked the same way.
> >>>>>>
> >>>>>> Lemme check this, but I think the issue rather in ordering when we apply fwnode
> >>>>>> to the newly created device and when we actually retrieve gpio-line-names
> >>>>>> property.
> >>>>>
> >>>>> Hmm... I can't see how it's possible can be. Can you provide a platform name
> >>>>> and pointers to the DTS that has been broken by the change?
> >>>>>
> >>>>
> >>>> I noticed it with gpio-mockup (libgpiod tests failed on v5.12-rc3) and
> >>>> the WiP gpio-sim - but it's the same on most DT platforms. The node
> >>>> that contains the `gpio-line-names` is the one associated with the
> >>>> platform device passed to the GPIO driver. The gpiolib then creates
> >>>> another struct device that becomes the child of that node but it
> >>>> doesn't copy the parent's properties to it (nor should it).
> >>>>
> >>>> Every driver that reads device properties does it from the parent
> >>>> device, not the one in gdev - whether it uses of_, fwnode_ or generic
> >>>> device_ properties.
> >>>
> >>> What you are telling contradicts with the idea of copying parent's fwnode
> >>> (or OF node) in the current code.
> >>>
> >>
> >> Ha! While the OF node of the parent device is indeed assigned to the
> >> gdev's dev, the same isn't done in the core code for fwnodes and
> >> simulated chips don't have an associated OF node, so this is the
> >> culprit I suppose.
> >
> > Close, but not fully correct.
> > First of all it depends on the OF / ACPI / platform enumeration.
> > Second, we are talking about secondary fwnode in the case where it happens.
> >
> > I'm in the middle of debugging this, I'll come up with something soon I believe.
>
> Was there ever any follow up on this ?
>
> I would like to point out that on STM32MP1 in Linux 5.10.y, the
> gpio-line-names are still broken, and a revert of "gpiolib: generalize
> devprop_gpiochip_set_names() for device properties" is still necessary.

Yes, Andy has fixed that in commit b41ba2ec54a7 ("gpiolib: Read
"gpio-line-names" from a firmware node") but for some reason this has
never made its way into stable. I'll resend it.

Bartosz