Message-ID: <3a54df71-d5cc-f538-75b8-f2193e27d65b@nvidia.com>
Date:   Mon, 9 Oct 2023 09:34:31 -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 10/8/23 11:48 PM, Bartosz Golaszewski wrote:
> On Thu, Oct 5, 2023 at 9:43 PM Dipen Patel <dipenp@...dia.com> wrote:
>>
>> 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?
>>
> 
> This is most likely going to be a longer discussion. I suggest that in
> the meantime you just assign the gc->fwnode pointer explicitly from
> the platform device in the tegra GPIO driver and use it in the lookup
> function. Note that this is NOT wrong or a hack. It's just that most
> devices don't need to be looked up using gpio_device_find().

Sure, at the same time, I am also find to use any other method/s.
> 
> Bart
> 
>>>
>>> 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
>>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>
>>>>
>>

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