phy: rockchip-inno-usb2: fix some race conditions

phy: rockchip-inno-usb2: fix some race conditions

There are some race conditions related to phy power on/off
and otg charger detection work, otg sm work. I can find at
least three race conditions at present.

Race condition[1]:
The first race condition involving phy power on/off which
may be caused by the following case.

Test on rk3399 evaluation board Type-C0, connect to PC usb
port with Type-C cable, then phy power on/off operation may
be done twice because of race condition between phy driver
and usb controller driver.

CPU 0:
- rockchip_usb2phy_bvalid_irq()
 - rockchip_usb2phy_otg_sm_work()
  - detect connect to PC usb, do phy power on
   - rockchip_usb2phy_power_on()

CPU 1:
- dwc3 driver do runtime resume process
 - dwc3_runtime_resume()
  - dwc3_core_init()
   - phy_power_on()
    - rockchip_usb2phy_power_on()

Although we use a suspended flag in rockchip_usb2phy_power_on()
to avoid doing the same things twice, but it's not enough to
prevent race condition if phy driver and usb controller driver
access the rockchip_usb2phy_power_on() at the same time. This
race condition may cause clk management unbalanced.

Race condition[2]:
The second race condition related to phy power on/off and otg
charger detection work. We need to keep the usb phy staying in
suspend mode when do usb charger detection. But now it don't
have any protection to prevent the other threads to operate phy
during charger detection.

The problem can also be easily reproduced on rk3399 evaluation
board Type-C0 when connect to PC usb port with Type-C cable.

CPU 0:
- rockchip_chg_detect_work()
 - power off phy and start to do charge detection work

CPU 1:
- dwc3 driver do runtime resume process
 - dwc3_runtime_resume()
  - dwc3_core_init()
   - phy_power_on()
    - power on phy again

This race condition may cause charger detection and later usb
enumeration abnormally.

Race condition[3]:
The third race condition involving otg sm work. The otg sm
work can be interrupted by bvalid irq, and the bvalid irq
handler rockchip_usb2phy_bvalid_irq() will do otg sm work,
which may cause unknown error.

This patch uses mutex lock to protect the phy operations,
otg charger detection work and otg sm work.

Change-Id: Ic6845a10b3e69fe9ae6cf0b2d4e2beb098232abd
Signed-off-by: William Wu <william.wu@rock-chips.com>