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From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Mon, 9 Oct 2023 08:48:56 +0200
Message-ID: <CAMRc=MfSGY691-sFhx8GeP43g0xGk1JzNa=9q5oemQoHHAM-5Q@mail.gmail.com>
Subject: Re: [RFT PATCH 14/21] hte: tegra194: don't access struct gpio_chip
To:     Dipen Patel <dipenp@nvidia.com>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        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 Thu, Oct 5, 2023 at 9:43=E2=80=AFPM Dipen Patel <dipenp@nvidia.com> wrot=
e:
>
> On 10/5/23 12:05 PM, Bartosz Golaszewski wrote:
> > On Thu, Oct 5, 2023 at 8:12=E2=80=AFPM Dipen Patel <dipenp@nvidia.com> =
wrote:
> >>
> >> On 10/5/23 6:48 AM, Bartosz Golaszewski wrote:
> >>> On Thu, Oct 5, 2023 at 1:52=E2=80=AFAM Dipen Patel <dipenp@nvidia.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=E2=80=AFAM Linus Walleij <linus.wall=
eij@linaro.org> wrote:
> >>>>>>>>>
> >>>>>>>>> On Tue, Sep 5, 2023 at 8:53=E2=80=AFPM Bartosz Golaszewski <brg=
l@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 r=
eference
> >>>>>>>>>> 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 som=
e
> >>>>>>>>> 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 t=
o 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() tree=
wide,
> >>>>>>>> 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 thi=
s, it failed
> >>>>>>> compilation at some spi/spi-bcm2835 driver. I disabled that and w=
as 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 gpi=
o device,
> >>>>>>> roughly around this place [1]. I thought it would be your patch s=
eries 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/lin=
ux.git/tree/drivers/hte/hte-tegra194.c?h=3Dfor-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-t=
egra194.c as
> >>>>> below:
> >>>>>
> >>>>> static int tegra_gpiochip_match(struct gpio_chip *chip, void *data)
> >>>>>  {
> >>>>> +       struct device_node *node =3D data;
> >>>>> +       struct fwnode_handle *fw =3D 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 n=
ame:%s\n",
> >>>>> __func__, __LINE__, chip->label, node->name, node->full_name, (chip=
->fwnode =3D=3D
> >>>>> fw), fw->dev->init_name);
> >>>>>         return chip->fwnode =3D=3D 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-tegra1=
86.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_d=
evice *pdev)
> >>>>                 offset +=3D port->pins;
> >>>>         }
> >>>>
> >>>> +       gpio->gpio.fwnode =3D 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 dr=
iver?
> >>>
> >>> You shouldn't need this. This driver already does:
> >>>
> >>>     gpio->gpio.parent =3D &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_* fun=
ction.
> >> The only reference I see is here [1]. Does it mean I need to change my=
 match
> >> function from:
> >>
> >> chip->fwnode =3D=3D of_node_to_fwnode(data)
> >>
> >> to:
> >> dev_fwnode(chip->parent) =3D=3D 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->fwno=
de
> 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().

Bart

> >
> > Bart
> >
> >>
> >> [1]:
> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tre=
e/drivers/gpio/gpiolib.c?h=3Dv6.6-rc1#n767
> >>
> >>>
> >>> Bart
> >>>
> >>>> 2) Or should I use something else in hte matching function instead o=
f fwnode so
> >>>> to avoid adding above line in the gpio driver?
> >>>>
> >>>>>
> >>>>>>>
> >>>>>>>>
> >>>>>>>> Bart
> >>>>>>>
> >>>>>>
> >>>>>
> >>>>
> >>
>