Messages in this thread |  | | Date | Tue, 23 Dec 2014 23:09:44 +0300 | From | Sergei Shtylyov <> | Subject | Re: [RFC/PATCH] extcon: otg_gpio: add driver for USB OTG port controlled by GPIO(s) |
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Hello.
On 12/23/2014 10:57 PM, 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.
You're using the cable state notifiers, why not control Vbus from there? You need some way of passing the GPIO to host driver though... I assume you're not using the device tree, and your host controllers live on PCI, so the platform data is out of question. You may be right then...
>>> (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.
http://marc.info/?l=linux-usb&m=141825413802370 In my case, Vbus is not controlled via GPIO though. I would have probably used the generic GPIO extcon driver if I didn't have to drive MAX3355's SHDN# pin high... There were also some other patches for this issue, the one probably interesting to you is there:
http://marc.info/?l=linux-usb&m=141877180912359
>>> Comments are welcome.
>>> Br, David
[...]
>>> +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.
What about deferred probing? With EPROBE_DEFER we don't need to play the initcall games any more AFAIU.
> Br, David
WBR, Sergei
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