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

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Message-ID: <0e7cae42-0b81-c038-8beb-49102feea8a6@nvidia.com>
Date:   Wed, 4 Oct 2023 16:51:55 -0700
From:   Dipen Patel <dipenp@...dia.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     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 10/4/23 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?
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
>>>
>>
>