Re: [PATCH] extcon: add MAX3355 driver

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

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...

[...]

>>> +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...

> [...]
>>> +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.

[...]

>>> +
>>> +    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...

[...]
>>> +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...

[...]

>> Thanks,
>> Chanwoo Choi

MBR, Sergei