linux-kernel - Re: [PATCH v4 02/15] gpio: regmap: set gpio_chip of

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Message-Id: <891B849E-32A0-4115-BCE9-2F0495274404@gmail.com>
Date:   Fri, 5 Mar 2021 08:45:40 +0100
From:   Álvaro Fernández Rojas <noltari@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list <bcm-kernel-feedback-list@...adcom.com>,
        Jonas Gorski <jonas.gorski@...il.com>,
        Necip Fazil Yildiran <fazilyildiran@...il.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 02/15] gpio: regmap: set gpio_chip of_node

Hi Andy,

> El 4 mar 2021, a las 17:33, Andy Shevchenko <andy.shevchenko@...il.com> escribió:
> 
> On Thu, Mar 4, 2021 at 5:44 PM Álvaro Fernández Rojas <noltari@...il.com> wrote:
>>> El 4 mar 2021, a las 16:28, Andy Shevchenko <andy.shevchenko@...il.com> escribió:
>>> On Thu, Mar 4, 2021 at 5:24 PM Álvaro Fernández Rojas <noltari@...il.com> wrote:
>>>>> El 4 mar 2021, a las 16:17, Andy Shevchenko <andy.shevchenko@...il.com> escribió:
>>>>> On Thu, Mar 4, 2021 at 5:06 PM Álvaro Fernández Rojas <noltari@...il.com> wrote:
>>>>>>> El 4 mar 2021, a las 11:35, Andy Shevchenko <andy.shevchenko@...il.com> escribió:
>>>>>>> On Thu, Mar 4, 2021 at 10:57 AM Álvaro Fernández Rojas
>>>>>>> <noltari@...il.com> wrote:
>>>>> 
>>>>>>>> + * @of_node:           (Optional) The device node
>>>>>>> 
>>>>>>>> +       struct device_node *of_node;
>>>>>>> 
>>>>>>> Can we use fwnode from day 1, please?
>>>>>> 
>>>>>> Could you explain this? I haven’t dealt with fwnode never :$
>>>>>> BTW, this is done to fix this check when parsing gpio ranges:
>>>>>> https://github.com/torvalds/linux/blob/f69d02e37a85645aa90d18cacfff36dba370f797/drivers/gpio/gpiolib-of.c#L933-L934
>>>>> 
>>>>> Use struct fwnode_handle pointer instead of OF-specific one.
>>>> 
>>>> But is that compatible with the current gpiolib-of code? :$
>>> 
>>> Yes (after a bit of amendment I have sent today as v2:
>>> https://lore.kernel.org/linux-gpio/20210304150215.80652-1-andriy.shevchenko@linux.intel.com/T/#u).
>> 
>> Well that doesn’t fulfill my definition of “current gpiolib-of code”…
>> @Linus what should I do about this?
> 
> Well, fwnode is a generic, and I strongly against spreading
> OF-specific code when we have fwnode working. But let's hear Linus
> out, of course!
> 
> But it seems you are right and the library needs a few more amendments.

Yes, but I’m trying to do as few amendments as possible since I already have quite a large amount of patches :)

> 
>>>>> Also here is the question, why do you need to have that field in the
>>>>> regmap config structure and can't simply use the parent's fwnode?
>>>>> Also I'm puzzled why it's not working w/o this patch: GPIO library
>>>>> effectively assigns parent's fwnode (okay, of_node right now).
>>>> 
>>>> Because gpio regmap a child node of the pin controller, which is the one probed (gpio regmap is probed from the pin controller).
>>>> Therefore the parent’s fwnode is useless, since the correct gpio_chip node is the child's one (we have pin-ranges declared in the child node, referencing the parent pinctrl node).
>>> 
>>> I see. Can you point me out to the code where we get the node and
>>> where it's being retrieved / filled?
>> 
>> Sure, this is where the child node is searched: https://github.com/Noltari/linux/blob/6d1ebb8ff26ed54592eef1fcd3b58834acb48c04/drivers/pinctrl/bcm/pinctrl-bcm63xx.c#L100-L109
>> Then the gpio child node is probed and assigned here: https://github.com/Noltari/linux/blob/6d1ebb8ff26ed54592eef1fcd3b58834acb48c04/drivers/pinctrl/bcm/pinctrl-bcm63xx.c#L51
> 
> So, this is not (*yet) in upstream, correct?

No it’s not, but I've already changed the approach several times and I’m starting to get tired about it...

> 
> So, why not to switch to fwnode API in that driver as well?
> 
> When you do that and supply fwnode thru the regmap configuration, in
> the gpio-regmap we may assign it to of_node (via to_of_node() API).
> 
>> Basically, I based that part of the code on the ingenic pin controller: https://github.com/torvalds/linux/blob/f69d02e37a85645aa90d18cacfff36dba370f797/drivers/pinctrl/pinctrl-ingenic.c#L2485-L2491
>> https://github.com/torvalds/linux/blob/f69d02e37a85645aa90d18cacfff36dba370f797/Documentation/devicetree/bindings/pinctrl/ingenic%2Cpinctrl.yaml#L155-L176
> 
> This doesn't use remgap GPIO.

Yes, I know, but there aren’t any pinctrl drivers using regmap GPIO right now, so I couldn’t base my code on anything else :)

> 
> -- 
> With Best Regards,
> Andy Shevchenko

Best regards,
Álvaro.