Re: [RFT PATCH 14/21] hte: tegra194: don't access struct gpio_chip

[Bartosz Golaszewski]

On Thu, Oct 5, 2023 at 1:52 AM Dipen Patel <dipenp@xxxxxxxxxx> 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@xxxxxxxxxx> wrote:
> >>>>>
> >>>>> On Tue, Sep 5, 2023 at 8:53 PM Bartosz Golaszewski <brgl@xxxxxxxx> wrote:
> >>>>>
> >>>>>> From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> >>>>>>
> >>>>>> 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@xxxxxxxxxx>
> >>>>>
> >>>>> As Andy points out add <linux/cleanup.h>, with that fixed:
> >>>>> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> >>>>>
> >>>>> 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?
>
> 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?

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
> >>>
> >>
> >
>