Re: [Regulator] Request for clarification - GPIO controlled regulator, USB VBUS,

[Åukasz Majewski]

Hi Dmitry,

> Hi Åukasz,
>
> On Tue, Oct 3, 2017 at 9:58 AM, Åukasz Majewski <l.majewski@xxxxxxxxx> wrote:
> > Dear All,
> >
> > Maybe somebody could shed some light to following issue:
> >
> > On my setup I do have USB connected touchscreen powered from VBUS.
> >
> > The VBUS power is controlled by a GPIO pin, which in turn is governed by
> > regulator API:
> >
> >          reg_usbh1_vbus: usb-h1-vbus {
> >                  compatible = "regulator-fixed";
> >                  gpio = <&gpio3 31 GPIO_ACTIVE_LOW>;
> >                  pinctrl-names = "default";
> >                  pinctrl-0 = <&pinctrl_usbh1_vbus>;
> >                  regulator-name = "usb_h1_vbus";
> >                  regulator-min-microvolt = <5000000>;
> >                  regulator-max-microvolt = <5000000>;
> >                  regulator-settling-time-us = <100000>;
> >          };
> >
> >
> > This regulator is then passed to USB controller:
> >
> > &usbh1 {
> >          vbus-supply = <&reg_usbh1_vbus>;
> >
> > }
> >
> > The regulator API starts VBUS -> USB host get info about the VBUS present
> > and starts enumeration of the USB device.
> >
> >
> > I would like to ask if there is any recommended way to remove VBUS power and
> > have a way to force from user space the touchscreen (re-)enumeration?
> >
> > As fair as I know the Regulator API is RO on purpose, so I cannot toggle
> > vbus from there.
> >
> > I could use hacks presented here (the userspace-regulator API):
> > https://patchwork.ozlabs.org/patch/374912/
> > https://lkml.org/lkml/2014/7/30/357
> >
> > but for some reason they did not find the way to the upstream. Also it seems
> > like such approach is for testing, not for production system.
> >
> >
> > I could write a "dummy" regulator driver, which would export control API to
> > /dev/sys/proc.
> > Something like:
> > http://elixir.free-electrons.com/linux/latest/source/drivers/usb/phy/phy-fsl-usb.c
> >
> > (but with opposite way).
> >
> > or ./drivers/input/misc/regulator-haptic.c
> >
> >
> > I've also tried the "usb" power control tricks;
> >
> > echo "0" > /sys/bus/usb/devices/usb1/power/autosuspend_delay_ms
> > echo "auto" > /sys/bus/usb/devices/usb1/power/control
> >
> > But without any effect (probably because of above dependencies).
> >
> >
> >
> > Have I overlooked something? Maybe there is any other mainline code, which I
> > could reuse?
> >
> >
> > My goal is to reuse as much as possible from ML and avoid developing any new
> > code :-)
>
> Please start from the beginning: it is not quite clear why you want
> the touchscreen to be re-enumerated.

The above setup generally works.

However, from time to time I do encounter some HID multi-touch driver 
initialization errors, which render the touchscreen unusable - e.g:

usb 1-1: input irq status -75 received
usb 1-1: reset low-speed USB device number 2 using ci_hdrc
expected 16 bytes, got -1

or

hid-generic 0003:19E2:2533.0002: unknown main item tag 0x0
hid-generic 0003:19E2:2533.0002: unknown main item tag 0x0
hid-generic 0003:19E2:2533.0002: unbalanced collection at end of report 
description
hid-generic: probe of 0003:19E2:2533.0002 failed with error -22


I've added 100 ms settle time for the VBUS regulator, but I'm not sure 
if it will fix this issue (I'm going to inspect VBUS voltage with 
oscilloscope).

Since I do have above errors, I thought that it would be feasible to 
have a "mean" to re-set VBUS voltage and force enumeration of the device.

I'm quite curious how USB connected touchscreens are controlled with 
USB's VBUS not accessible from user-space out of the box?

> Thanks.


--
Best regards.

Åukasz Majewski