Date:	Fri, 20 Feb 2015 07:41:37 +0100
From:	Robert Baldyga <r.baldyga@...sung.com>
To:	David Cohen <david.a.cohen@...ux.intel.com>,
	myungjoo.ham@...sung.com, cw00.choi@...sung.com
Cc:	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	baolu.lu@...ux.intel.com
Subject: Re: [PATCH v2] extcon: otg_gpio: add driver for USB OTG port
 controlled by GPIO(s)

Hi David,

On 02/19/2015 08:59 PM, David Cohen wrote:
> Some Intel platforms have an USB OTG port fully (or partially)
> controlled by GPIOs:
> 
> (1) USB ID is connected directly to a pulled up GPIO.
> 
> Optionally:
> (2) VBUS is enabled/disabled by a GPIO
> (3) Platform has 2 USB controllers connected to same port: one for
>     device and one for host role. D+/- are switched between phys.
>     according to this GPIO level.
> 
> This driver configures USB OTG port for device or host role according to
> USB ID value.
>  - If USB ID's GPIO level is low, OTG port is configured for host role
>    by sourcing VBUS and switching D+/- to host phy.
>  - If USB ID's GPIO level is high, by standard, the OTG port is
>    configured for device role by not sourcing VBUS and switching D+/- to
>    device controller.

IMO it's not very elegant to handle VBUS power on/off in extcon driver.
Creating fixed regulator would allow to make VBUS handling more generic.
Then extcon client could handle VBUS regulator. Also D+/- routing would
be separated but I don't see better place for it.

Odroid platforms also uses GPIO for USB cable detection so your driver
would be useful in that case. I created some simple driver for it but I
see I could use your driver after adding VBUS detection.

BTW don't you have VBUS detection on your board? It would allow to
distinguish between USB, USB-Host and disconnected states.

--
Robert

> 
> Signed-off-by: David Cohen <david.a.cohen@...ux.intel.com>
> ---
> 
> Hi,
> 
> Since splitting this driver into smaller pieces would result in ugly fixes WRT
> ACPI, I'm resending the same approach.
> This time I addressed all comments I got from RFC version.
> 
> As always, comments are welcome.
> 
> Br, David
> ---
> 
>  drivers/extcon/Kconfig           |   8 ++
>  drivers/extcon/Makefile          |   1 +
>  drivers/extcon/extcon-otg_gpio.c | 186 +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 195 insertions(+)
>  create mode 100644 drivers/extcon/extcon-otg_gpio.c
> 
> diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
> index 6a1f7de6fa54..986ca7da9c1b 100644
> --- a/drivers/extcon/Kconfig
> +++ b/drivers/extcon/Kconfig
> @@ -63,6 +63,14 @@ config EXTCON_MAX8997
>  	  Maxim MAX8997 PMIC. The MAX8997 MUIC is a USB port accessory
>  	  detector and switch.
>  
> +config EXTCON_OTG_GPIO
> +	tristate "VIRTUAL USB OTG PORT support"
> +	depends on GPIOLIB && ACPI
> +	help
> +	  Say Y here to enable support for virtual USB OTG port device
> +	  controlled by GPIOs. This driver can be used when at least USB ID pin
> +	  is connected directly to GPIO.
> +
>  config EXTCON_PALMAS
>  	tristate "Palmas USB EXTCON support"
>  	depends on MFD_PALMAS
> diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
> index 0370b42e5a27..0d5b152b51ea 100644
> --- a/drivers/extcon/Makefile
> +++ b/drivers/extcon/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_EXTCON_GPIO)	+= extcon-gpio.o
>  obj-$(CONFIG_EXTCON_MAX14577)	+= extcon-max14577.o
>  obj-$(CONFIG_EXTCON_MAX77693)	+= extcon-max77693.o
>  obj-$(CONFIG_EXTCON_MAX8997)	+= extcon-max8997.o
> +obj-$(CONFIG_EXTCON_OTG_GPIO)	+= extcon-otg_gpio.o
>  obj-$(CONFIG_EXTCON_PALMAS)	+= extcon-palmas.o
>  obj-$(CONFIG_EXTCON_RT8973A)	+= extcon-rt8973a.o
>  obj-$(CONFIG_EXTCON_SM5502)	+= extcon-sm5502.o
> diff --git a/drivers/extcon/extcon-otg_gpio.c b/drivers/extcon/extcon-otg_gpio.c
> new file mode 100644
> index 000000000000..7dfa2c15b562
> --- /dev/null
> +++ b/drivers/extcon/extcon-otg_gpio.c
> @@ -0,0 +1,186 @@
> +/*
> + * Virtual USB OTG Port driver controlled by gpios
> + *
> + * Copyright (c) 2014, Intel Corporation.
> + * Author: David Cohen <david.a.cohen@...ux.intel.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/acpi.h>
> +#include <linux/extcon.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +
> +#define DRV_NAME	"usb_otg_port"
> +
> +struct vuport {
> +	struct device *dev;
> +	struct gpio_desc *gpio_vbus_en;
> +	struct gpio_desc *gpio_usb_id;
> +	struct gpio_desc *gpio_usb_mux;
> +
> +	struct extcon_dev edev;
> +};
> +
> +static const char *vuport_extcon_cable[] = {
> +	[0] = "USB-Host",
> +	NULL,
> +};
> +
> +/*
> + * If id == 1, USB port should be set to peripheral
> + * if id == 0, USB port should be set to host
> + *
> + * Peripheral: set USB mux to peripheral and disable VBUS
> + * Host: set USB mux to host and enable VBUS
> + */
> +static void vuport_set_port(struct vuport *vup, int id)
> +{
> +	int mux_val = id;
> +	int vbus_val = !id;
> +
> +	if (!IS_ERR(vup->gpio_usb_mux))
> +		gpiod_direction_output(vup->gpio_usb_mux, mux_val);
> +
> +	if (!IS_ERR(vup->gpio_vbus_en))
> +		gpiod_direction_output(vup->gpio_vbus_en, vbus_val);
> +}
> +
> +static void vuport_do_usb_id(struct vuport *vup)
> +{
> +	int id = gpiod_get_value(vup->gpio_usb_id);
> +
> +	dev_info(vup->dev, "USB PORT ID: %s\n", id ? "PERIPHERAL" : "HOST");
> +
> +	/*
> +	 * id == 1: PERIPHERAL
> +	 * id == 0: HOST
> +	 */
> +	vuport_set_port(vup, id);
> +
> +	/*
> +	 * id == 0: HOST connected
> +	 * id == 1: Host disconnected
> +	 */
> +	extcon_set_cable_state(&vup->edev, "USB-Host", !id);
> +}
> +
> +static irqreturn_t vuport_thread_isr(int irq, void *priv)
> +{
> +	struct vuport *vup = priv;
> +
> +	vuport_do_usb_id(vup);
> +	return IRQ_HANDLED;
> +}
> +
> +#define VUPORT_GPIO_USB_ID	0
> +#define VUPORT_GPIO_VBUS_EN	1
> +#define VUPORT_GPIO_USB_MUX	2
> +static int vuport_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct vuport *vup;
> +	int ret;
> +
> +	vup = devm_kzalloc(dev, sizeof(*vup), GFP_KERNEL);
> +	if (!vup) {
> +		dev_err(dev, "cannot allocate private data\n");
> +		return -ENOMEM;
> +	}
> +	vup->dev = dev;
> +
> +	vup->gpio_usb_id = devm_gpiod_get_index(dev, "id", VUPORT_GPIO_USB_ID);
> +	if (IS_ERR(vup->gpio_usb_id)) {
> +		dev_err(dev, "cannot request USB ID GPIO: ret = %ld\n",
> +			PTR_ERR(vup->gpio_usb_id));
> +		return PTR_ERR(vup->gpio_usb_id);
> +	}
> +
> +	ret = gpiod_direction_input(vup->gpio_usb_id);
> +	if (ret < 0) {
> +		dev_err(dev, "cannot set input direction to USB ID GPIO: ret = %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	vup->gpio_vbus_en = devm_gpiod_get_index(dev, "vbus en",
> +						 VUPORT_GPIO_VBUS_EN);
> +	if (IS_ERR(vup->gpio_vbus_en))
> +		dev_dbg(dev, "cannot request VBUS EN GPIO, skipping it.\n");
> +
> +	vup->gpio_usb_mux = devm_gpiod_get_index(dev, "usb mux",
> +						 VUPORT_GPIO_USB_MUX);
> +	if (IS_ERR(vup->gpio_usb_mux))
> +		dev_dbg(dev, "cannot request USB USB MUX, skipping it.\n");
> +
> +	/* register extcon device */
> +	vup->edev.dev.parent = dev;
> +	vup->edev.supported_cable = vuport_extcon_cable;
> +	ret = extcon_dev_register(&vup->edev);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to register extcon device: ret = %d\n",
> +			ret);
> +		return ret;
> +	}
> +
> +	ret = devm_request_threaded_irq(dev, gpiod_to_irq(vup->gpio_usb_id),
> +					NULL, vuport_thread_isr,
> +					IRQF_SHARED | IRQF_TRIGGER_RISING |
> +					IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
> +					dev_name(dev), vup);
> +	if (ret < 0) {
> +		dev_err(dev, "cannot request IRQ for USB ID GPIO: ret = %d\n",
> +			ret);
> +		goto irq_err;
> +	}
> +	vuport_do_usb_id(vup);
> +
> +	platform_set_drvdata(pdev, vup);
> +
> +	dev_dbg(dev, "driver successfully probed\n");
> +
> +	return 0;
> +
> +irq_err:
> +	extcon_dev_unregister(&vup->edev);
> +
> +	return ret;
> +}
> +
> +static int vuport_remove(struct platform_device *pdev)
> +{
> +	struct vuport *vup = platform_get_drvdata(pdev);
> +
> +	extcon_dev_unregister(&vup->edev);
> +	return 0;
> +}
> +
> +static struct acpi_device_id vuport_acpi_match[] = {
> +	{ "INT3496" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(acpi, vuport_acpi_match);
> +
> +static struct platform_driver vuport_driver = {
> +	.driver = {
> +		.name = DRV_NAME,
> +		.acpi_match_table = ACPI_PTR(vuport_acpi_match),
> +	},
> +	.probe = vuport_probe,
> +	.remove = vuport_remove,
> +};
> +
> +module_platform_driver(vuport_driver);
> +
> +MODULE_LICENSE("GPLv2");
> +MODULE_AUTHOR("David Cohen <david.a.cohen@...ux.intel.com>");
> 

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