Re: [RFT 0/3] usb: usb3503: Fix probing on Arndale board (missing phy)

[Marek Szyprowski]

Hello,

On 2015-10-08 08:02, Krzysztof Kozlowski wrote:
> On 07.10.2015 23:26, Marek Szyprowski wrote:
> > Hello,
> >
> > On 2015-10-07 02:30, Krzysztof Kozlowski wrote:
> > > Introduction
> > > ============
> > > This patchset tries to fix probing of usb3503 on Arndale board
> > > if the Samsung PHY driver is probed later (or built as a module).
> > >
> > > *The patchset was not tested on Arndale board.*
> > > I don't have that board. Please test it and say if the usb3503
> > > deferred probe
> > > works fine and the issue is solved.
> > >
> > > The patchset was tested on Odroid U3 board (which is different!)
> > > in a simulated environment. It is not sufficient testing.
> > >
> > >
> > > Difference
> > > ==========
> > > The usb3503 device driver can be used as a I2C device (on Odroid U3)
> > > or as a platform device connected through phy (on Arndale). In the second
> > > case the necessary phy reference has to be obtained and enabled.
> > >
> > > For some details please look also at thread [0][1].
> > >
> > > [0]
> > > http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/348524.html
> > >
> > > [1]
> > > http://lists.infradead.org/pipermail/linux-arm-kernel/2015-June/348875.html
> > I'm not sure that this is the correct approach. usb3503 chip is simply
> > connected
> > to Exynos USB2 phy, so it visible on the USB bus. The real driver that
> > controls USB2
> > PHY is Exynos EHCI driver and USB3503 should not mess around it.
> The ehci node (usb@12110000) has one port configured and it takes one
> PHY reference (phy of id 1 - USB host). I can't see driver taking
> reference to HSIC0 or HSIC1 phys... Since I cannot diagnose the error I
> don't know what is really expected here.

It looks that EHCI in Exynos 5250 and 5420 still use old phy bindings. For
the reference, see Exynos4 dts and exynos4412-odroidu3.dts to check how 
to enable
more than one USB port (Odroid U3 has both HSIC ports enabled).

> > In my opinion all that is needed in case of Arndale board is forcing
> > reset of
> > usb3503 chip after successful EHCI and USB2 PHY initialization (for some
> > reason
> > initialization of usb3503 chip must be done after usb host initialization).
> > However I have no idea which driver should trigger this reset. Right now
> > I didn't
> > find any good solution for additional control for devices which are on
> > autoprobed
> > bus like usb.
> The reset is done at the end of usb3503's probe. The question "why
> usb3503 has to be initialized after EHCI and USB PHY" is still valid...

I remember that I saw some code to reset HSIC device after phy power on 
in case
of HSIC-connected modem chip, so maybe this is somehow common for HSIC chips
(which are some special case of 'embedded usb').

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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