Re: [PATCH v3 1/7] extcon: usb-gpio: Introduce gpio usb extcon driver

[Roger Quadros]

Chanwoo,

On 30/01/15 02:06, Chanwoo Choi wrote:
> Hi Roger,
> 
> On 01/29/2015 08:26 PM, Roger Quadros wrote:
>> Chanwoo,
>>
>> On 29/01/15 03:49, Chanwoo Choi wrote:
>>> Hi Roger,
>>>
>>> We need to discuss one point about 'id_irqwake'.
>>> I don't recommend to use 'id_irqwake' field.
>>>
>>> And I catch build warning by using "select" keywork in Kconfig.
>>> It is my wrong guide of "select" keyword. So, I'll change it 
>>> as 'depends on' keyword.
>>>
>>> Looks good to me except for 'id_irqwake'. 
>>> I'll apply this patch on 3.21 queue after completing this discussion.
>>>
>>> On 01/28/2015 09:15 PM, Roger Quadros wrote:
>>>> This driver observes the USB ID pin connected over a GPIO and
>>>> updates the USB cable extcon states accordingly.
>>>>
>>>> The existing GPIO extcon driver is not suitable for this purpose
>>>> as it needs to be taught to understand USB cable states and it
>>>> can't handle more than one cable per instance.
>>>>
>>>> For the USB case we need to handle 2 cable states.
>>>> 1) USB (attach/detach)
>>>> 2) USB-Host (attach/detach)
>>>>
>>>> This driver can be easily updated in the future to handle VBUS
>>>> events in case it happens to be available on GPIO for any platform.
>>>>
>>>> Signed-off-by: Roger Quadros <rogerq@xxxxxx>
>>>> ---
>>>> v3:
>>>> - removed IRQF_NO_SUSPEND flag. Added IRQF_TRIGGER_RISING and
>>>>   IRQF_TRIGGER_FALLING
>>>> - Added disable_irq() to suspend() and enable_irq() to resume()
>>>>
>>>>  .../devicetree/bindings/extcon/extcon-usb-gpio.txt |  18 ++
>>>>  drivers/extcon/Kconfig                             |   7 +
>>>>  drivers/extcon/Makefile                            |   1 +
>>>>  drivers/extcon/extcon-usb-gpio.c                   | 233 +++++++++++++++++++++
>>>>  4 files changed, 259 insertions(+)
>>>>  create mode 100644 Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
>>>>  create mode 100644 drivers/extcon/extcon-usb-gpio.c
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt b/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
>>>> new file mode 100644
>>>> index 0000000..85fe6b0
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/extcon/extcon-usb-gpio.txt
>>>> @@ -0,0 +1,18 @@
>>>> +USB GPIO Extcon device
>>>> +
>>>> +This is a virtual device used to generate USB cable states from the USB ID pin
>>>> +connected to a GPIO pin.
>>>> +
>>>> +Required properties:
>>>> +- compatible: Should be "linux,extcon-usb-gpio"
>>>> +- id-gpio: gpio for USB ID pin. See gpio binding.
>>>> +
>>>> +Example:
>>>> +	extcon_usb1 {
>>>> +		compatible = "linux,extcon-usb-gpio";
>>>> +		id-gpio = <&gpio6 1 GPIO_ACTIVE_HIGH>;
>>>> +	}
>>>> +
>>>> +	&omap_dwc3_1 {
>>>> +		extcon = <&extcon_usb1>;
>>>> +	};
>>>> diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
>>>> index 6a1f7de..fd11536 100644
>>>> --- a/drivers/extcon/Kconfig
>>>> +++ b/drivers/extcon/Kconfig
>>>> @@ -93,4 +93,11 @@ config EXTCON_SM5502
>>>>  	  Silicon Mitus SM5502. The SM5502 is a USB port accessory
>>>>  	  detector and switch.
>>>>  
>>>> +config EXTCON_USB_GPIO
>>>> +	tristate "USB GPIO extcon support"
>>>> +	select GPIOLIB
>>>
>>> I catch the build warning if using 'select' instead of 'depends on' as following:
>>> It is my wrong guide to you. So, I'll modify it by using "depends on" as your original patch.
>>
>> OK. Thanks.
>>
>>>
>>> make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- zImage  -j 8
>>> scripts/kconfig/conf --silentoldconfig Kconfig
>>> drivers/gpio/Kconfig:34:error: recursive dependency detected!
>>> drivers/gpio/Kconfig:34:	symbol GPIOLIB is selected by EXTCON_USB_GPIO
>>> drivers/extcon/Kconfig:96:	symbol EXTCON_USB_GPIO depends on EXTCON
>>> drivers/extcon/Kconfig:1:	symbol EXTCON is selected by CHARGER_MANAGER
>>> drivers/power/Kconfig:316:	symbol CHARGER_MANAGER depends on POWER_SUPPLY
>>> drivers/power/Kconfig:1:	symbol POWER_SUPPLY is selected by HID_SONY
>>> drivers/hid/Kconfig:670:	symbol HID_SONY depends on NEW_LEDS
>>> drivers/leds/Kconfig:8:	symbol NEW_LEDS is selected by BCMA_DRIVER_GPIO
>>> drivers/bcma/Kconfig:75:	symbol BCMA_DRIVER_GPIO depends on GPIOLIB
>>>
>>>> +	help
>>>> +	  Say Y here to enable GPIO based USB cable detection extcon support.
>>>> +	  Used typically if GPIO is used for USB ID pin detection.
>>>> +
>>>>  endif # MULTISTATE_SWITCH
>>>> diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
>>>> index 0370b42..6a08a98 100644
>>>> --- a/drivers/extcon/Makefile
>>>> +++ b/drivers/extcon/Makefile
>>>> @@ -12,3 +12,4 @@ obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o
>>>>  obj-$(CONFIG_EXTCON_PALMAS)	+= extcon-palmas.o
>>>>  obj-$(CONFIG_EXTCON_RT8973A)	+= extcon-rt8973a.o
>>>>  obj-$(CONFIG_EXTCON_SM5502)	+= extcon-sm5502.o
>>>> +obj-$(CONFIG_EXTCON_USB_GPIO)	+= extcon-usb-gpio.o
>>>> diff --git a/drivers/extcon/extcon-usb-gpio.c b/drivers/extcon/extcon-usb-gpio.c
>>>> new file mode 100644
>>>> index 0000000..99a58b2
>>>> --- /dev/null
>>>> +++ b/drivers/extcon/extcon-usb-gpio.c
>>>> @@ -0,0 +1,233 @@
>>>> +/**
>>>> + * drivers/extcon/extcon-usb-gpio.c - USB GPIO extcon driver
>>>> + *
>>>> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
>>>> + * Author: Roger Quadros <rogerq@xxxxxx>
>>>> + *
>>>> + * This program is free software; you can redistribute it and/or modify
>>>> + * it under the terms of the GNU General Public License version 2 as
>>>> + * published by the Free Software Foundation.
>>>> + *
>>>> + * This program is distributed in the hope that it will be useful,
>>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>>>> + * GNU General Public License for more details.
>>>> + */
>>>> +
>>>> +#include <linux/extcon.h>
>>>> +#include <linux/init.h>
>>>> +#include <linux/interrupt.h>
>>>> +#include <linux/irq.h>
>>>> +#include <linux/kernel.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/of_gpio.h>
>>>> +#include <linux/platform_device.h>
>>>> +#include <linux/slab.h>
>>>> +#include <linux/workqueue.h>
>>>> +
>>>> +#define USB_GPIO_DEBOUNCE_MS	20	/* ms */
>>>> +
>>>> +struct usb_extcon_info {
>>>> +	struct device *dev;
>>>> +	struct extcon_dev *edev;
>>>> +
>>>> +	struct gpio_desc *id_gpiod;
>>>> +	int id_irq;
>>>> +	bool id_irqwake;		/* ID wakeup enabled flag */
>>>
>>> Do you really think id_irqwake is necessary?
>>> I think it is not necessary.
>>
>> I will explain below why it is necessary.
>>
>>>
>>>> +
>>>> +	unsigned long debounce_jiffies;
>>>> +	struct delayed_work wq_detcable;
>>>> +};
>>>> +
>>>> +/* List of detectable cables */
>>>> +enum {
>>>> +	EXTCON_CABLE_USB = 0,
>>>> +	EXTCON_CABLE_USB_HOST,
>>>> +
>>>> +	EXTCON_CABLE_END,
>>>> +};
>>>> +
>>>> +static const char *usb_extcon_cable[] = {
>>>> +	[EXTCON_CABLE_USB] = "USB",
>>>> +	[EXTCON_CABLE_USB_HOST] = "USB-Host",
>>>> +	NULL,
>>>> +};
>>>> +
>>>
>>> [snip]
>>>
>>>> +
>>>> +static int usb_extcon_remove(struct platform_device *pdev)
>>>> +{
>>>> +	struct usb_extcon_info *info = platform_get_drvdata(pdev);
>>>> +
>>>> +	cancel_delayed_work_sync(&info->wq_detcable);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +#ifdef CONFIG_PM_SLEEP
>>>> +static int usb_extcon_suspend(struct device *dev)
>>>> +{
>>>> +	struct usb_extcon_info *info = dev_get_drvdata(dev);
>>>> +
>>>> +	if (device_may_wakeup(dev))
>>>> +		if (!enable_irq_wake(info->id_irq))
>>>> +			info->id_irqwake = true;
>>>> +
>>>
>>> You can simplify this code as following without 'id_irqwake':
>>>
>>> 	if (device_may_wakeup(dev))
>>> 		enable_irq_wake(info->id_irq);
>>
>> enable_irq_wake() can fail. And if it does we need to keep track of it
>> to prevent unbalanced disable_irq_wake() call in resume().
>> That's the reason I've added the id_irqwake flag in struct usb_extcon_info.
> 
> It is not proper solution using id_irqwake. If fail to execute enable_irq_wake(),
> usb_extcon_suspend() function have to return error immediately.
> 

Your point is valid. I will now need to investigate why enable_irq_wake() is failing
when used for GPIO of PCA857x on DRA7-evm.

cheers,
-roger

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