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Date: Thu, 29 Jan 2015 13:26:39 +0200
From: Roger Quadros <rogerq@...com>
To: Chanwoo Choi <cw00.choi@...sung.com>
CC: <myungjoo.ham@...sung.com>, <balbi@...com>, <tony@...mide.com>,
<george.cherian@...com>, <nsekhar@...com>,
<devicetree@...r.kernel.org>, <linux-usb@...r.kernel.org>,
<linux-omap@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/7] extcon: usb-gpio: Introduce gpio usb extcon driver
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@...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@...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.
>
>> + /*
>> + * We don't want to process any IRQs after this point
>> + * as GPIOs used behind I2C subsystem might not be
>> + * accessible until resume completes. So disable IRQ.
>> + */
>> + disable_irq(info->id_irq);
>> +
>> + return 0;
>> +}
>> +
>> +static int usb_extcon_resume(struct device *dev)
>> +{
>> + struct usb_extcon_info *info = dev_get_drvdata(dev);
>> +
>> + if (info->id_irqwake) {
>> + disable_irq_wake(info->id_irq);
>> + info->id_irqwake = false;
>> + }
>
> ditto.
>
> if (device_may_wakeup(dev))
> disable_irq_wake(info->id_irq);
>
>> +
>> + enable_irq(info->id_irq);
>> +
>> + return 0;
>> +}
>> +#endif
>> +
>> +static SIMPLE_DEV_PM_OPS(usb_extcon_pm_ops,
>> + usb_extcon_suspend, usb_extcon_resume);
>> +
>> +static struct of_device_id usb_extcon_dt_match[] = {
>> + { .compatible = "linux,extcon-usb-gpio", },
>> + { /* sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, usb_extcon_dt_match);
>> +
>> +static struct platform_driver usb_extcon_driver = {
>> + .probe = usb_extcon_probe,
>> + .remove = usb_extcon_remove,
>> + .driver = {
>> + .name = "extcon-usb-gpio",
>> + .pm = &usb_extcon_pm_ops,
>> + .of_match_table = usb_extcon_dt_match,
>> + },
>> +};
>> +
>> +module_platform_driver(usb_extcon_driver);
>> +
>> +MODULE_AUTHOR("Roger Quadros <rogerq@...com>");
>> +MODULE_DESCRIPTION("USB GPIO extcon driver");
>> +MODULE_LICENSE("GPL v2");
>>
>
cheers,
-roger
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