Re: [PATCH 4/7] phy: meson: add USB2 PHY support for Meson8b and GXBB

Martin Blumenstingl [off-list ref] writes:

On Tue, Sep 13, 2016 at 5:28 PM, Philipp Zabel [off-list ref] wrote:

[...]

quoted

quoted

I added Philipp and Hans to this thread - maybe they can comment on this.
To sum it up, our problem is:
- there are two separate USB PHYs on Meson GXBB
- both are sharing the same reset line (provided by the reset-meson driver)
- during initialization of the PHYs we must only call
reset_control_reset(rstc) once (if we do it for the first *and* second
PHY then the first PHY gets confused once the second PHY uses the
reset because the first PHY's state is reset as well)

If you have an initially asserted reset line and you can enable the
first module by deasserting the reset via reset_control_deassert (and
reset_control_assert to signal when the module may be disabled again
after use), shared resets are for you.

If you need a reset pulse or have no direct control over the reset line,
(device_reset), the reset framework currently has no solution for this.
The ugly thing about reset_control_once would be that it can't re-reset
modules when unloading and reloading driver modules.

The corresponding reset driver in question is reset-meson, which only
implements reset (assert/deassert are not implemented). However, I
don't know if this is due to hardware design.
I think the hardware implements the latter, but maybe Neil can give
more information here (I currently don't have access to my board so I
cannot test how the hardware actually behaves).

It's implemented that way because the hardware only supports a reset
pulse.

Kevin
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