Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
Message-ID: <681ddbf9-baeb-9876-8615-5ec8a4b6c368@redhat.com>
Date:   Wed, 27 Sep 2023 15:17:45 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.13.0
Subject: Re: [RFT PATCH 2/4] platform/x86: int3472: led: don't use
 gpiod_toggle_active_low()
Content-Language: en-US
From:   Hans de Goede <hdegoede@redhat.com>
To:     Bartosz Golaszewski <brgl@bgdev.pl>
Cc:     Mika Westerberg <mika.westerberg@linux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        Daniel Scally <djrscally@gmail.com>,
        Mark Gross <markgross@kernel.org>, linux-gpio@vger.kernel.org,
        linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
        platform-driver-x86@vger.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
References: <20230926145943.42814-1-brgl@bgdev.pl>
 <20230926145943.42814-3-brgl@bgdev.pl>
 <2b5db794-c00f-e9f5-c0c9-4c5fb4df0802@redhat.com>
 <CAMRc=MeSK-ZReyt4556Dik4GwgtitD-NBgVE0swe=4i+5gBLwA@mail.gmail.com>
 <3f8760f8-ae8c-c0b0-19d7-76fbbf5d25de@redhat.com>
In-Reply-To: <3f8760f8-ae8c-c0b0-19d7-76fbbf5d25de@redhat.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

Hi Again,

On 9/27/23 15:08, Hans de Goede wrote:
> Hi Bart,
> 
> On 9/27/23 12:44, Bartosz Golaszewski wrote:
>> On Wed, Sep 27, 2023 at 11:40 AM Hans de Goede <hdegoede@redhat.com> wrote:
>>>
>>> Hi,
>>>
>>> On 9/26/23 16:59, Bartosz Golaszewski wrote:
>>>> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>>>
>>>> Instead of acpi_get_and_request_gpiod() + gpiod_toggle_active_low(), use
>>>> temporary lookup tables with appropriate lookup flags.
>>>>
>>>> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>>>> ---
>>>>  drivers/platform/x86/intel/int3472/led.c | 12 ++++--------
>>>>  1 file changed, 4 insertions(+), 8 deletions(-)
>>>>
>>>> diff --git a/drivers/platform/x86/intel/int3472/led.c b/drivers/platform/x86/intel/int3472/led.c
>>>> index bca1ce7d0d0c..62e0cd5207a7 100644
>>>> --- a/drivers/platform/x86/intel/int3472/led.c
>>>> +++ b/drivers/platform/x86/intel/int3472/led.c
>>>> @@ -25,18 +25,14 @@ int skl_int3472_register_pled(struct int3472_discrete_device *int3472,
>>>>       if (int3472->pled.classdev.dev)
>>>>               return -EBUSY;
>>>>
>>>> -     int3472->pled.gpio = acpi_get_and_request_gpiod(path, agpio->pin_table[0],
>>>> -                                                          "int3472,privacy-led");
>>>> +     int3472->pled.gpio = skl_int3472_gpiod_get_from_temp_lookup(
>>>> +                             int3472->dev, path, agpio->pin_table[0],
>>>> +                             "int3472,privacy-led", polarity,
>>>> +                             GPIOD_OUT_LOW);
>>>
>>> Yeah so this is not going to work, path here is an ACPI device path, e.g.
>>> on my laptop (which actually uses the INT3472 glue code) the path-s of
>>> the 2 GPIO controllers are: `\_SB_.GPI0` resp `\_SB_.PC00.XHCI.RHUB.HS08.VGPO`
>>>
>>> Where as skl_int3472_gpiod_get_from_temp_lookup() stores the passed in path
>>> in  gpiod_lookup_table.table[0].key, which is the dev_name() of the GPIO
>>> controller's parent dev which are `INTC1055:00` resp. `INTC1096:00` .
>>>
>>> So we are going to need to add some code to INT3472 to go from path to
>>> a correct value for gpiod_lookup_table.table[0].key which means partly
>>> reproducing most of acpi_get_gpiod:
>>>
>>>         struct gpio_chip *chip;
>>>         acpi_handle handle;
>>>         acpi_status status;
>>>
>>>         status = acpi_get_handle(NULL, path, &handle);
>>>         if (ACPI_FAILURE(status))
>>>                 return ERR_PTR(-ENODEV);
>>>
>>>         chip = gpiochip_find(handle, acpi_gpiochip_find);
>>>         if (!chip)
>>>                 return ERR_PTR(-EPROBE_DEFER);
>>>
>>> And then get the key from the chip. Which means using gpiochip_find
>>> in the int3472 code now, which does not sound like an improvement.
>>>
>>> I think that was is needed instead is adding an active_low flag
>>> to acpi_get_and_request_gpiod() and then have that directly
>>> set the active-low flag on the returned desc.
>>>
>>
>> Ultimately I'd like everyone to use gpiod_get() for getting
>> descriptors but for now I get it's enough. Are you find with this
>> being done in a single patch across GPIO and this driver?
> 
> Yes doing this in a single patch is fine.
> 
> Also I'm fine with merging such a patch through the gpio tree .

So thinking about this more I realized that the int3472 code already
generates GPIO lookups for the sensor device for some
(powerdown, reset) GPIOs, it only needs the gpio_desc for
the case where the GPIO is turned into a regulator, clock or led.

Since the int3472 code is already generating lookups it already
has a way to go from path to a lookup "key":

        status = acpi_get_handle(NULL, path, &handle);
        if (ACPI_FAILURE(status))
                return -EINVAL;

        adev = acpi_fetch_acpi_dev(handle);
        if (!adev)
                return -ENODEV;

        table_entry->key = acpi_dev_name(adev);

So we can get the key without needing to call gpio_find_chip()

So I do believe that the temp lookup approach should actually
work. I'm currently traveling, so no promises but I should
be able to rework your series in something which actually
works and which will:

1. Stop using gpiod_toggle_active_low()
2. Allow dropping acpi_get_and_request_gpiod()

So no need for a patch to add an active-low parameter to
acpi_get_and_request_gpiod(), sorry about the noise.

Regards,

Hans


>>>>       if (IS_ERR(int3472->pled.gpio))
>>>>               return dev_err_probe(int3472->dev, PTR_ERR(int3472->pled.gpio),
>>>>                                    "getting privacy LED GPIO\n");
>>>>
>>>> -     if (polarity == GPIO_ACTIVE_LOW)
>>>> -             gpiod_toggle_active_low(int3472->pled.gpio);
>>>> -
>>>> -     /* Ensure the pin is in output mode and non-active state */
>>>> -     gpiod_direction_output(int3472->pled.gpio, 0);
>>>> -
>>>>       /* Generate the name, replacing the ':' in the ACPI devname with '_' */
>>>>       snprintf(int3472->pled.name, sizeof(int3472->pled.name),
>>>>                "%s::privacy_led", acpi_dev_name(int3472->sensor));
>>>
>>