Re: [PATCH] extcon: add MAX3355 driver

[Chanwoo Choi <cw00.choi@samsung.com>]

On 2015년 10월 21일 03:20, Sergei Shtylyov wrote:
> Hello.
> 
> On 12/18/2014 12:58 AM, Sergei Shtylyov wrote:
> 
>>>> MAX3355E chip integrates a charge pump and comparators to enable a system with
>>>> an integrated USB OTG dual-role transceiver to function as a USB OTG dual-role
>>>> device. In addition to sensing/controlling Vbus, the chip also passes thru the
>>>> ID signal from the USB OTG connector.  On some Renesas boards, this signal  is
>>>> just  fed into the SoC thru a GPIO pin -- there's no real OTG controller, only
>>>> host and gadget USB controllers sharing the same USB bus; however,  we'd  like
>>>> to allow host or gadget drivers to be loaded depending on the cable type,
>>>> hence
>>>> the need for the MAX3355 extcon driver. The Vbus status signals are also wired
>>>> to GPIOs (however, we're not currently intested in them), the  OFFVBUS# signal
>>>> is controlled  by the host controllers, there's also the SHDN# signal wired to
>>>> GPIO, which should be high for normal operation.
>>
>>>> Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
>>
>>>> ---
>>>> The patch is against the 'extcon-next' branch of the 'extcon.git' repo.
>>
>>>>   Documentation/devicetree/bindings/extcon/extcon-max3355.txt |   21 ++
>>>>   drivers/extcon/Kconfig                                      |    6
>>>>   drivers/extcon/Makefile                                     |    1
>>>>   drivers/extcon/extcon-max3355.c                             |  122
>>>> ++++++++++++
>>>>   4 files changed, 150 insertions(+)
>>
>>>> Index: extcon/Documentation/devicetree/bindings/extcon/extcon-max3355.txt
>>>> =================================>>>> --- /dev/null
>>>> +++ extcon/Documentation/devicetree/bindings/extcon/extcon-max3355.txt
>>>> @@ -0,0 +1,21 @@
>>>> +MAX3355 USB OTG chip
>>
>>> Need manufactor information as following :
>>>    -> Maxim MAX3355
>>
>>     Would be Maxim enough? Or perhaps I should use Maxim Integrated [Products]?
> 
>    You haven't replied to my questions.
> 
>>>> +--------------------
>>>> +
>>>> +MAX3355 integrates a charge pump and comparators to enable a system with an
>>>> +integrated USB OTG dual-role transceiver to function as a USB OTG dual-role
>>>> +device.
>>>> +
>>>> +Required properties:
>>>> +- compatible: should be "maxim,max3355";
>>>> +- maxim,shdn-gpio: should contain a phandle and GPIO specifier for the
>>>> GPIO pin
>>>> +  connected to the MAX3355's SHDN# pin;
>>>> +- maxim,id-gpio: should contain a phandle and GPIO specifier for the GPIO pin
>>>> +  connected to the MAX3355's ID_OUT pin.
>>>> +
>>>> +Example (Koelsch board):
>>>> +
>>>> +    usb-otg {
>>>> +        compatible = "maxim,max3355";
>>>> +        maxim,shdn-gpio = <&gpio2 4 GPIO_ACTIVE_LOW>;
>>>> +        maxim,id-gpio = <&gpio5 31 GPIO_ACTIVE_HIGH>;
>>
>>> Kernel already supported the gpio helper function to get gpio from devicetree.
>>> I prefer use follwoing style by using of_get_gpio()/of_get_gpio_flags() in
>>> include/linux/of_gpio.h.
>>
>>>         gpios = <&gpio2 4 GPIO_ACTIVE_LOW>, <&gpio5 31 GPIO_ACTIVE_HIGH>;
>>
>>     OK, though Documentation/devicetree/bindings/gpio/gpio.txt does not seem
>> to insist on using this one...
> 
>    Moreover, it now says "gpios" isn't allowed for the new bindings. So I have to strongly disagree here...

OK. But, I recommend you use the 'gpiod' with devm_gpiod_get
instead of using devm_gpio_request_one() directly as following:
You can refer drivers/extcon/extcon-usb-gpio.c about using gpiod.

For example,
	data->shdn_gpiod = devm_gpiod_get(dev, "maxim,shdn", GPIOD_IN);
	data->id_gpiod = devm_gpiod_get(dev, "maxim,id", GPIOD_IN);

> 
> [...]
> 
>>>> +static irqreturn_t max3355_id_irq(int irq, void *dev_id)
>>>> +{
>>>> +    struct max3355_data *data = dev_id;
>>>> +    int id = gpio_get_value(data->id_gpio);
>>>> +
>>>> +    extcon_set_cable_state(data->edev, "USB-HOST", !id);
>>
>>> You have to get the gpio flag in the devicetree by using of_get_gpio_flags()
>>> function
>>> and then you would set the cable state according to gpio state and flag.
>>
>>     I'm sorry but I just don't see why I have to do it. This is not a generic
>> GPIO driver, and the polarities of the GPIOs are determined solely by the
>> MAX3355 specs.
> 
>    Again, got not reply...

OK. you don't need to consider the gpio flag from devicetree.

> 
>> [...]
>>>> +static int max3355_probe(struct platform_device *pdev)
>>>> +{
>>>> +    struct device_node *np = pdev->dev.of_node;
>>>> +    struct max3355_data *data;
>>>> +    int gpio, irq, ret;
>>>> +
>>>> +    data = devm_kzalloc(&pdev->dev, sizeof(struct max3355_data),
>>>> +                GFP_KERNEL);
>>>> +    if (!data)
>>>> +        return -ENOMEM;
>>>> +
>>>> +    data->edev = devm_extcon_dev_allocate(&pdev->dev, max3355_cable);
>>>> +    if (IS_ERR(data->edev)) {
>>>> +        dev_err(&pdev->dev, "failed to allocate extcon device\n");
>>>> +        return PTR_ERR(data->edev);
>>>> +    }
>>>> +    data->edev->name = kstrdup(np->name, GFP_KERNEL);
>>>> +
>>>> +    gpio = of_get_named_gpio(np, "maxim,id-gpio", 0);
>>
>>> Use of_get_gpio() or of_get_gpio_flags().
>>
>>     OK, I'll use the first one.
> 
>    No, I won't due to not being able to use "gpios" anymore.

OK. I add the comment on upper. You can use the gpiod API.

> 
> [...]
> 
>>>> +
>>>> +    ret = devm_request_threaded_irq(&pdev->dev, irq, NULL, max3355_id_irq,
>>>> +                    IRQF_TRIGGER_RISING |
>>>> +                    IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
>>
>>> Is it right to add both RISING and FALLING trigger?
>>
>>     How else I'm supposed to know when the OTG ID signal goes low and high?
>>
>>> and need to add IRQF_NO_SUSPEND to wakeup from suspend state when interrupt
>>> happen.
>>
>>     Hm, are you sure we want to wake up on plugging another kind of USB cable?
> 
>    No reply to that as well...

I'm sure. If external connector (USB, Charger cable, Earjack etc..)
is attached or detached in the suspended state, system should be wake-up
from suspended state.

If kernel don't handle the any interrupt in suspended state,
after wakeup from suspended state, there is mismatch data
between 'before entering suspend state' and 'after wakeup from suspend state'.

> 
> [...]
>>>> +static struct platform_driver max3355_driver = {
>>>> +    .probe        = max3355_probe,
>>>> +    .driver        = {
>>>> +        .name    = "extcon-max3355",
>>>> +        .of_match_table = max3355_match_table,
>>>> +        .owner    = THIS_MODULE,
>>>> +    },
>>>> +};
>>>> +
>>>> +module_platform_driver(max3355_driver);
>>>> +
>>
>>> Don't need un-used blank line.
>>
>>     I don't understand. There's empty line in such case in extcon-gpio.c...
> 
>    No reply...

OK. No problem. Ignore this comment.

Thanks,
Chanwoo Choi