linux-kernel - Re: [RFT PATCH 14/21] hte: tegra194: don't access struct gpio

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Date:   Thu, 5 Oct 2023 11:12:37 -0700
From:   Dipen Patel <dipenp@...dia.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>,
        Tony Lindgren <tony@...mide.com>,
        Russell King <linux@...linux.org.uk>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <markgross@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-acpi@...r.kernel.org, timestamp@...ts.linux.dev,
        linux-tegra@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [RFT PATCH 14/21] hte: tegra194: don't access struct gpio_chip

On 10/5/23 6:48 AM, Bartosz Golaszewski wrote:
> On Thu, Oct 5, 2023 at 1:52 AM Dipen Patel <dipenp@...dia.com> wrote:
>>
>> On 10/4/23 3:54 PM, Dipen Patel wrote:
>>> On 10/4/23 1:33 PM, Dipen Patel wrote:
>>>> On 10/4/23 1:30 PM, Dipen Patel wrote:
>>>>> On 10/4/23 5:00 AM, Bartosz Golaszewski wrote:
>>>>>> On Thu, Sep 7, 2023 at 9:28 AM Linus Walleij <linus.walleij@...aro.org> wrote:
>>>>>>>
>>>>>>> On Tue, Sep 5, 2023 at 8:53 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>>>>>>>
>>>>>>>> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>>>>>>
>>>>>>>> Using struct gpio_chip is not safe as it will disappear if the
>>>>>>>> underlying driver is unbound for any reason. Switch to using reference
>>>>>>>> counted struct gpio_device and its dedicated accessors.
>>>>>>>>
>>>>>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>>>>>>>
>>>>>>> As Andy points out add <linux/cleanup.h>, with that fixed:
>>>>>>> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
>>>>>>>
>>>>>>> I think this can be merged into the gpio tree after leaving some
>>>>>>> slack for the HTE maintainer to look at it, things look so much
>>>>>>> better after this.
>>>>>>>
>>>>>>> Yours,
>>>>>>> Linus Walleij
>>>>>>
>>>>>> Dipen,
>>>>>>
>>>>>> if you could give this patch a test and possibly ack it for me to take
>>>>>> it through the GPIO tree (or go the immutable tag from HTE route) then
>>>>>> it would be great. This is the last user of gpiochip_find() treewide,
>>>>>> so with it we could remove it entirely for v6.7.
>>>>>
>>>>> Progress so far for the RFT...
>>>>>
>>>>> I tried applying the patch series on 6.6-rc1 and it did not apply cleanly,
>>>>> some patches I needed to manually apply and correct. With all this, it failed
>>>>> compilation at some spi/spi-bcm2835 driver. I disabled that and was able to
>>>>> compile. I thought I should let you know this part.
>>>>>
>>>>> Now, I tried to test the hte and it seems to fail finding the gpio device,
>>>>> roughly around this place [1]. I thought it would be your patch series so
>>>>> tried to just use 6.6rc1 without your patches and it still failed at the
>>>>> same place. I have to trace back now from which kernel version it broke.
>>>>
>>>> [1].
>>>> https://git.kernel.org/pub/scm/linux/kernel/git/pateldipen1984/linux.git/tree/drivers/hte/hte-tegra194.c?h=for-next#n781
>>>>
>>>> of course with your patches it would fail for the gdev instead of the chip.
>>>
>>> Small update:
>>>
>>> I put some debugging prints in the gpio match function in the hte-tegra194.c as
>>> below:
>>>
>>> static int tegra_gpiochip_match(struct gpio_chip *chip, void *data)
>>>  {
>>> +       struct device_node *node = data;
>>> +       struct fwnode_handle *fw = of_node_to_fwnode(data);
>>> +       if (!fw || !chip->fwnode)
>>> +               pr_err("dipen patel: fw is null\n");
>>>
>>> -       pr_err("%s:%d\n", __func__, __LINE__);
>>> +       pr_err("dipen patel, %s:%d: %s, %s, %s, match?:%d, fwnode name:%s\n",
>>> __func__, __LINE__, chip->label, node->name, node->full_name, (chip->fwnode ==
>>> fw), fw->dev->init_name);
>>>         return chip->fwnode == of_node_to_fwnode(data);
>>>  }
>>>
>>> The output of the printfs looks like below:
>>> [    3.955194] dipen patel: fw is null -----> this message started appearing
>>> when I added !chip->fwnode test in the if condition line.
>>>
>>> [    3.958864] dipen patel, tegra_gpiochip_match:689: tegra234-gpio, gpio,
>>> gpio@...0000, match?:0, fwnode name:(null)
>>>
>>> I conclude that chip->fwnode is empty. Any idea in which conditions that node
>>> would be empty?
>>
>> sorry for spamming, one last message before I sign off for the day....
>>
>> Seems, adding below in the tegra gpio driver resolved the issue I am facing, I
>> was able to verify your patch series.
>>
>> diff --git a/drivers/gpio/gpio-tegra186.c b/drivers/gpio/gpio-tegra186.c
>> index d87dd06db40d..a56c159d7136 100644
>> --- a/drivers/gpio/gpio-tegra186.c
>> +++ b/drivers/gpio/gpio-tegra186.c
>> @@ -989,6 +989,8 @@ static int tegra186_gpio_probe(struct platform_device *pdev)
>>                 offset += port->pins;
>>         }
>>
>> +       gpio->gpio.fwnode = of_node_to_fwnode(pdev->dev.of_node);
>> +
>>         return devm_gpiochip_add_data(&pdev->dev, &gpio->gpio, gpio);
>>  }
>>
>> Now, few follow up questions:
>> 1) is this the correct way of setting the chip fwnode in the gpio driver?
> 
> You shouldn't need this. This driver already does:
> 
>     gpio->gpio.parent = &pdev->dev;
> 
> so fwnode should be assigned in gpiochip_add_data_with_key(). Can you
> check why this doesn't happen?

I do not see anywhere chip->fwnode being set in the gpiochip_add_* function.
The only reference I see is here [1]. Does it mean I need to change my match
function from:

chip->fwnode == of_node_to_fwnode(data)

to:
dev_fwnode(chip->parent) == of_node_to_fwnode(data)?

[1]:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpio/gpiolib.c?h=v6.6-rc1#n767

> 
> Bart
> 
>> 2) Or should I use something else in hte matching function instead of fwnode so
>> to avoid adding above line in the gpio driver?
>>
>>>
>>>>>
>>>>>>
>>>>>> Bart
>>>>>
>>>>
>>>
>>