Re: [linux-sunxi] Re: [PATCH 1/4] phy: sun4i-usb: support PHY0 on H3 in MUSB mode

[Hans de Goede]

HI,

On 19-01-17 21:27, Karsten Merker wrote:
> On Thu, Jan 19, 2017 at 11:10:08PM +0800, Icenowy Zheng wrote:
> > 19.01.2017, 22:34, "Maxime Ripard" <maxime.ripard@xxxxxxxxxxxxxxxxxx>:
> > > On Wed, Jan 18, 2017 at 04:09:32AM +0800, Chen-Yu Tsai wrote:
> > > >  On Wed, Jan 18, 2017 at 4:06 AM, Maxime Ripard
> > > >  <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote:
> > > >  > On Wed, Jan 18, 2017 at 12:57:08AM +0800, Icenowy Zheng wrote:
> > > >  >> 17.01.2017, 16:06, "Maxime Ripard" <maxime.ripard@xxxxxxxxxxxxxxxxxx>:
> > > >  >> > On Tue, Jan 17, 2017 at 03:14:46AM +0800, Icenowy Zheng wrote:
> > > >  >> >> The PHY0 on H3 can be wired either to MUSB controller or OHCI/EHCI
> > > >  >> >> controller.
> > > >  >> >>
> > > >  >> >> The original driver wired it to OHCI/EHCI controller; however, as the
> > > >  >> >> code to use PHY0 as OHCI/EHCI is missing, it makes the PHY fully
> > > >  >> >> unusable.
> > > >  >> >>
> > > >  >> >> Rename the register (according to its function and the name in BSP
> > > >  >> >> driver), and remove the code which wires the PHY0 to OHCI/EHCI, as MUSB
> > > >  >> >> can support both peripheral and host mode (although the host mode of
> > > >  >> >> MUSB is buggy).
> > > >  >> >
> > > >  >> > Can you elaborate on that? What's wrong with it?
> > > >  >>
> > > >  >> The configuration is at bit 0 of register 0x20 in PHY.
> > > >  >>
> > > >  >> When the PHY is reseted, it defaults as MUSB mode.
> > > >  >>
> > > >  >> However, the original author of the H3 PHY code seems to be lack of
> > > >  >> this knowledge (He named it PHY_UNK_H3), and changed the PHY to HCI
> > > >  >> mode.
> > > >  >>
> > > >  >> I just removed the code that wires it to HCI mode, thus it will work
> > > >  >> in MUSB mode, with my sun8i-h3-musb patch.
> > > >  >
> > > >  > I have no idea what you mean by MUSB mode.
> > > >  >
> > > >  > Do you mean that the previous code was only working in host mode, and
> > > >  > now it only works in peripheral?
> > > >
> > > >  From what I understand, with the H3, Allwinner has put a mux
> > > >  in front of the MUSB controller. The mux can send the USB data
> > > >  to/from the MUSB controller, or a standard EHCI/OHCI pair.
> > > >  This register controls said mux.
> > > >
> > > >  This means we can use a proper USB host for host mode,
> > > >  instead of the limited support in MUSB.
> > >
> > > But musb can still operate as a host, right?
> >
> > Yes!
>
> Hello,
>
> I don't know how the MUSB implementation in the H3 behaves as I
> don't have any H3-based systems, but if it should happen to be
> similar to the one in the A31s, it probably isn't a full-fledged
> alternative to using an OHCI/EHCI controller.

You right it isn't which is why I suggested that the phy-sun4i-usb
code should set the mux to the OCHI/EHCI pair when the id pin
is pulled low (host-mode).

> From my practical experiments with the MUSB in the A31s in host
> mode I can report that I hadn't been able to get multiple HIDs
> (in my case keyboard and mouse) working at the same time.  The
> keyboard alone worked without problems, the mouse alone worked
> without problems, but when both were connected, only one of them
> worked.
>
> I had at that time talked to Hans de Goede about the problem and
> if I remenber correctly, he had mentioned that the MUSB has
> problems servicing more than one device that does interrupt
> transfers (as HIDs do).
>
> Hans, can you perhaps shed some light on this?

Everything you've said is correct, the MUSB can emulate a
host-controller, but it is not really one and when possible
should not be used as such.

Regards,

Hans