Missing USB clock for BCM2835

Eric Anholt eric at anholt.net
Sun Jul 24 17:13:24 PDT 2016

Stefan Wahren <stefan.wahren at i2se.com> writes:

> Hi,
> i'm working on Raspberry Pi Zero support (incl. OTG / Gadget). I wanted to add
> the missing clock control for DWC2 [1], but i didn't find a matching clock in
> the clock tree.
> The BCM2835 clk driver contains the define A2W_XOSC_CTRL_USB_ENABLE, but no
> separate registers. So i assume USB clock is a child of xosc only with a gate
> and a fixed frequency of 480 MHz.

Yeah, I believe OSC is used as the refclk for USB.  I'm not sure I trust
that that bit is the actual enable bit -- the clock manager docs look
like they've got some bad copy-and-paste around those bits and I think
they've been only partially updated for 2835.
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