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

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Message-ID: <5bf6771d-5783-0a40-5a72-7ddbb9c694aa@denx.de>
Date:   Sat, 10 Apr 2021 02:45:58 +0200
From:   Marek Vasut <marex@...x.de>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        "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 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.