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

[Roger Quadros <rogerq@ti.com>]

+Thomas (for irq/dummychip.c question)

Hi,

On 30/01/15 13:09, Roger Quadros wrote:
> 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@ti.com>
>>>>> ---
>>>>> 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@ti.com>
>>>>> + *
>>>>> + * 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.
> 

The reason of enable_irq_wake() failure with PCA857x is that it uses dummy_irq_chip which
doesn't have irq_set_wake() or IRQCHIP_SKIP_SET_WAKE flag set.

I can send out another patch to add IRQCHIP_SKIP_SET_WAKE to dummy_irq_chip.

Thomas, is this a reasonable option?

The problem at hand is that enable_irq_wake() on a IRQ line based off PCA857x GPIO chip fails.
PCA857x uses dummy_irq_chip to implement the IRQ feature.
http://lxr.free-electrons.com/source/drivers/gpio/gpio-pcf857x.c#L227

cheers,
-roger