On Wed, Sep 14, 2016 at 10:42:50AM -0700, Stephen Boyd wrote:

quoted

quoted

Hmm.. maybe the confusion is in which registers we should be able to
access? Are we talking about the ULPI viewport MMIO register space or
the ULPI registers that we access through the viewport? I have a
hw_phymode_configure() inside of of ci_ulpi_init() so that the
identification registers through the ULPI viewport read properly
(assuming there aren't other power requirements like regulators). If we
don't set the portsc.pts before using the viewport, the viewport doesn't
work and reads timeout. So we really don't touch the ULPI registers
except for the scratch space and the id registers until after the phy is
properly powered on with clks and regulators, because the only place we
touch them after doing the id checking is in this phy driver in
qcom_usb_hs_phy_power_on(). We've "solved" the chicken-egg problem where
we don't know which device driver to probe because the phy needs to be
powered on to read the id registers to know which device driver to use
by using DT to match up device drivers instead.

[1] https://www.sparkfun.com/datasheets/Components/SMD/ULPI_v1_1.pdf

Ok, ulpi phy works like USB device on USB bus which create device at
runtime. So, like some hard-wired USB devices, it may needs power
sequence too, otherwise, how it knows which driver can loads.

Yes. We use the DT compatible string to ignore any issues with reading
the device ids when the device is powered off. Unlike USB though, we
have device drivers for the ULPI PHYs that do the power sequencing along
with other initializations, so using a common pwrseq layer seems like
overkill just so we can read the id registers.

If the attempt to read id registers will not hang the system, it can
work. Like the case [1], without PHY ref_clk, it will hang when
configure PHY mode (visit portsc.pts), it has no chance to read id
registers. So, I still think the ULPI bus driver needs to do power
sequence for its children, unless you have some place to open the
ref_clk.

Are there any concerns with this patch? Or can they be reapplied?

For this patch, it is ok for me.


[1] http://www.spinics.net/lists/linux-usb/msg146336.html
-- 

Best Regards,
Peter Chen