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

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Date:   Thu, 5 Oct 2023 12:43:13 -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 12:05 PM, Bartosz Golaszewski wrote:
> On Thu, Oct 5, 2023 at 8:12 PM Dipen Patel <dipenp@...dia.com> wrote:
>>
>> 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)?
> 
> No! chip->fwnode is only used to let GPIOLIB know which fwnode to
> assign to the GPIO device (struct gpio_device).
What do you suggest I should use for the match as I do not see chip->fwnode
being set?

> 
> Bart
> 
>>
>> [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
>>>>>>>
>>>>>>
>>>>>
>>>>
>>