USB PHY documentation

[Martin Blumenstingl]

Hello,

last weekend I tried getting the USB PHY working on my GXBB device.
The simple part: resetting the USB part and enabling the clocks.
The tricky part: configuring the USB PHY registers

Unfortunately the public datasheet does not contain any information
about the USB PHY.
The reference driver does not contain many comments, the struct
members are using abbreviated names and it seems that a part of what
should be done by the PHY driver is part of the dwc driver
(usb_peri_reg changes were patched into it).
I am now wondering if someone can share some details from the datasheet.

I took my register #defines from the reference driver (and tried to
make them human readable): [0]
There are some USB_PHY_CLK_SEL_* definitions at the bottom which seem
interesting (at least for configuring REG_CONFIG_CLK_SEL, but
unfortunately I don't know if these are valid (for either meson8b or
gxbb)..

Symptoms are: dwc2's USB initialization is successful, but when I plug
in a device it's not being detected.
I *think* that my problem is that REG_ADP_BC_DRV_VBUS is a readonly
bit - it's set when I use the original firmware of my device, but I
cannot set it in my PHY driver.

In case anyone is interested how my changes look exactly, you can find
the code here: [1]

I also dumped the USB PHY registers from the original Android firmware
of my device in case anyone is interested:
phy0:
[0xc0000000] = 0x8000
[0xc0000004] = 0x1690500
[0xc0000008] = 0x0
[0xc000000c] = 0x8E18
[0xc0000010] = 0x0
[0xc0000014] = 0x80000
[0xc0000018] = 0x246613D
[0xc000001c] = 0x0

phy1:
[0xc0000020] = 0x8000
[0xc0000024] = 0x1690500
[0xc0000028] = 0x0
[0xc000002c] = 0x2010118
[0xc0000030] = 0x0
[0xc0000034] = 0x80000
[0xc0000038] = 0xE46613D
[0xc000003c] = 0x0

@Ben: did you get anywhere with your experiments on Meson8b (S805)?


Regards,
Martin


[0] https://github.com/150balbes/Amlogic_s905-kernel/blob/master/include/linux/amlogic/usb-meson8.h
[1] https://github.com/xdarklight/linux/commit/a1666af7fdb48734784fa368d568fd4209c5b125