Date: Tue, 23 Dec 2014 11:57:09 -0800
From: David Cohen <david.a.cohen@linux.intel.com>
To: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: myungjoo.ham@samsung.com, cw00.choi@samsung.com,
        linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
        baolu.lu@linux.intel.com
Subject: Re: [RFC/PATCH] extcon: otg_gpio: add driver for USB OTG port
 controlled by GPIO(s)
Message-ID: <20141223195709.GA19996@psi-dev26.jf.intel.com>
References: <1419288217-19262-1-git-send-email-david.a.cohen@linux.intel.com>
 <549969D4.5020303@cogentembedded.com>
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Hi Sergei,

On Tue, Dec 23, 2014 at 04:10:44PM +0300, Sergei Shtylyov wrote:
> Hello.
> 
> On 12/23/2014 1:43 AM, David Cohen wrote:
> 
> >Some platforms have an USB OTG port fully (or partially) controlled by
> >GPIOs:
> 
> >(1) USB ID is connected directly to GPIO
> 
> >Optionally:
> >(2) VBUS is enabled by a GPIO (when ID is grounded)
> 
>    Can't the host driver still control Vbus?

I can't a clean way for host driver to control VBUS considering it
depends on USB ID.

> 
> >(3) Platform has 2 USB controllers connected to same port: one for
> >     device and one for host role. D+/- are switched between phys
> >     by GPIO.
> 
> >As per initial version, this driver has the duty to control whether
> >USB-Host cable is plugged in or not:
> >  - If yes, OTG port is configured for host role
> >  - If no, by standard, the OTG port is configured for device role
> 
> >Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
> >---
> 
> >Hi,
> 
> >Some Intel Bay Trail boards have an unusual way to handle the USB OTG port:
> >  - The USB ID pin is connected directly to GPIO on SoC
> >  - When in host role, VBUS is provided by enabling a GPIO
> >  - Device and host roles are supported by 2 independent controllers with D+/-
> >    pins from port switched between different phys according a GPIO level.
> 
> >The ACPI table describes this USB port as a (virtual) device with all the
> >necessary GPIOs. This driver implements support to this virtual device as an
> >extcon class driver. All drivers that depend on the USB OTG port state (USB phy,
> >PMIC, charge detection) will listen to extcon events.
> 
>    It's very close to my setup on R-Car R8A7791 based boards. :-)
> I have already submitted Maxim MAX3355 OTG chip GPIO-based driver.

Hm. I'll look for it. Thanks for pointing.

> 
> >Comments are welcome.
> 
> >Br, David
> >---
> >
> >  drivers/extcon/Kconfig           |   8 ++
> >  drivers/extcon/Makefile          |   1 +
> >  drivers/extcon/extcon-otg_gpio.c | 200 +++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 209 insertions(+)
> >  create mode 100644 drivers/extcon/extcon-otg_gpio.c
> >
> >diff --git a/drivers/extcon/Kconfig b/drivers/extcon/Kconfig
> >index 6a1f7de6fa54..e8010cda4642 100644
> >--- a/drivers/extcon/Kconfig
> >+++ b/drivers/extcon/Kconfig
> >@@ -93,4 +93,12 @@ config EXTCON_SM5502
> >  	  Silicon Mitus SM5502. The SM5502 is a USB port accessory
> >  	  detector and switch.
> >
> >+config EXTCON_OTG_GPIO
> >+	tristate "VIRTUAL USB OTG PORT support"
> >+	depends on GPIOLIB
> >+	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.
> >+
> 
>    The entries in this file seem alphabetically sorted.

I'll fix it.

> 
> >  endif # MULTISTATE_SWITCH
> >diff --git a/drivers/extcon/Makefile b/drivers/extcon/Makefile
> >index 0370b42e5a27..9e81088c6584 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_OTG_GPIO) += extcon-otg_gpio.o
> 
>    The lines here are sorted too.

Ditto.

> 
> >diff --git a/drivers/extcon/extcon-otg_gpio.c b/drivers/extcon/extcon-otg_gpio.c
> >new file mode 100644
> >index 000000000000..c5ee765a5f4f
> >--- /dev/null
> >+++ b/drivers/extcon/extcon-otg_gpio.c
> >@@ -0,0 +1,200 @@
> [...]
> >+static irqreturn_t vuport_isr(int irq, void *priv)
> >+{
> >+	return IRQ_WAKE_THREAD;
> >+}
> 
>    It's the same as the default IRQ handler...
> 
> >+	ret = devm_request_threaded_irq(dev, gpiod_to_irq(vup->gpio_usb_id),
> >+					vuport_isr, vuport_thread_isr,
> 
>    ... so you probably can just pass NULL instead of vuport_isr, no?

I'll review that.

> 
> [...]
> 
> >+static int __init vuport_init(void)
> >+{
> >+	return platform_driver_register(&vuport_driver);
> >+}
> >+subsys_initcall(vuport_init);
> 
>    Hm, why?

We have drivers that depend on this one during their probe.

Br, David

> 
> WBR, Sergei
> 
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