Re: [PATCH] extcon: add MAX3355 driver

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

Hi Sergei,

I think this patch is too much delay. I recommend you better to develop
this driver based on latest extcon-next branch[1].
[1] https://git.kernel.org/cgit/linux/kernel/git/chanwoo/extcon.git/log/?h=extcon-next

Thanks,
Chanwoo Choi

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