[PATCH v2 0/3] USB: add generic onboard USB HUB driver

[Maciej S. Szmigiero]

On 17.12.2015 07:57, Peter Chen wrote:
> On Wed, Dec 16, 2015 at 09:05:35PM +0100, Maciej S. Szmigiero wrote:
>> Hi Fabio,
>> Hi Peter,
>>
>> On 16.12.2015 11:11, Fabio Estevam wrote:
>>> Hi Peter,
>>>
>>> On Wed, Dec 16, 2015 at 2:11 AM, Peter Chen <peter.chen at freescale.com> wrote:
>>>
>>>> Thanks, Fabio, but I am curious how things like that? The USBOH3 clock
>>>> is not opened, the usb driver will hang when it tries to access
>>>> registers. If this clock is always on, then, why the system will
>>>> hang later?
>>>
>>> I found the issue with your patch. You missed to add the pinctrl node.
>>>
>>> With the change below USB is functional in Udoo:
>>>
>>> --- a/arch/arm/boot/dts/imx6qdl-udoo.dtsi
>>> +++ b/arch/arm/boot/dts/imx6qdl-udoo.dtsi
>>> @@ -22,6 +22,8 @@
>>>
>>>         usb_hub1 {
>>>                 compatible = "generic-onboard-hub";
>>> +               pinctrl-names = "default";
>>> +               pinctrl-0 = <&pinctrl_usbh>;
>>>                 clocks = <&clks IMX6QDL_CLK_CKO>;
>>>                 reset-gpios = <&gpio7 12 GPIO_ACTIVE_LOW>;
>>>                 reset-duration-us = <2>;
>>>
>>
>> Thanks for your work, I didn't notice it previously (sorry).
>>
>> I can confirm, too that with Peter's patches and the above change
>> the USB support works again on my UDOO DualLite board.
>>
>> However, I noticed that when you have host USB support configured to be
>> build as modules then (due to its location under "if USB") it is only
>> possible to compile generic onboard USB HUB as module, too.
>>
>> Then this module would need to be loaded before loading USB support
>> (or quickly after it), otherwise USB enumeration would time out after
>> few secs and loading it later wouldn't help.
> 
> Thanks for testing it, it maybe this hardware limitation.
> The USB device should be back to work whenever do hardware reset,
> otherwise, this reset is not clean.

I looked deeper into it and looks like the reset GPIO have to be
explicitly configured as output and also the reset pulse duration
have to be longer in order for hub the successfully reset and reattach
to USB host (at least on the one UDOO board that I have).

The shortest working time seems to be 3000us - 2000us didn't work even
when I changed GPIO pin mode to fast and drive strength to maximum.

Summing up, this change allows me to load generic_onboard_hub driver
in any order with respect to USB host modules:
--- a/arch/arm/boot/dts/imx6qdl-udoo.dtsi
+++ b/arch/arm/boot/dts/imx6qdl-udoo.dtsi
@@ -26,7 +26,7 @@
 		pinctrl-0 = <&pinctrl_usbh>;
 		clocks = <&clks IMX6QDL_CLK_CKO>;
 		reset-gpios = <&gpio7 12 GPIO_ACTIVE_LOW>;
-		reset-duration-us = <2>;
+		reset-duration-us = <3000>;
 	};
 };
 
--- a/drivers/usb/misc/generic_onboard_hub.c
+++ b/drivers/usb/misc/generic_onboard_hub.c
@@ -89,7 +89,7 @@ static int usb_hub_generic_probe(struct platform_device *pdev)
 	of_property_read_u32(node, "reset-duration-us", &duration_us);
 
 	if (gpiod_reset) {
-		gpiod_set_value(gpiod_reset, 1);
+		gpiod_direction_output(gpiod_reset, 1);
 		usleep_range(duration_us, duration_us + 10);
 		gpiod_set_value(gpiod_reset, 0);
 	}


Best regards,
Maciej Szmigiero