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

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Message-ID: <CAMRc=Mc_+LxcbV+=KPwAh4DinJAAetHrK+W3jbNp4AZBzg63TA@mail.gmail.com>
Date:   Thu, 5 Oct 2023 21:05:34 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Dipen Patel <dipenp@...dia.com>
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 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).

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
> >>>>>
> >>>>
> >>>
> >>
>