Hi Dmitry,
Hi Łukasz,
On Tue, Oct 3, 2017 at 9:58 AM, Łukasz 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 = <®_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.
Łukasz Majewski
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