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Message-ID: <90b5f887-8af4-a80d-ea4d-cf2199752de4@nvidia.com>
Date:   Wed, 4 Oct 2023 15:54:24 -0700
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Subject: Re: [RFT PATCH 14/21] hte: tegra194: don't access struct gpio_chip
Content-Language: en-US
From:   Dipen Patel <dipenp@nvidia.com>
To:     Bartosz Golaszewski <brgl@bgdev.pl>,
        Linus Walleij <linus.walleij@linaro.org>
Cc:     Aaro Koskinen <aaro.koskinen@iki.fi>,
        Janusz Krzysztofik <jmkrzyszt@gmail.com>,
        Tony Lindgren <tony@atomide.com>,
        Russell King <linux@armlinux.org.uk>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Jonathan Hunter <jonathanh@nvidia.com>,
        Hans de Goede <hdegoede@redhat.com>,
        Mark Gross <markgross@kernel.org>,
        linux-arm-kernel@lists.infradead.org, linux-omap@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org,
        linux-acpi@vger.kernel.org, timestamp@lists.linux.dev,
        linux-tegra@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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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@linaro.org> wrote:
>>>>
>>>> On Tue, Sep 5, 2023 at 8:53 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>>>>
>>>>> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.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@linaro.org>
>>>>
>>>> As Andy points out add <linux/cleanup.h>, with that fixed:
>>>> Reviewed-by: Linus Walleij <linus.walleij@linaro.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@c2f0000, match?:0, fwnode name:(null)

I conclude that chip->fwnode is empty. Any idea in which conditions that node
would be empty?

>>
>>>
>>> Bart
>>
>