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

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Date:   Thu, 19 Jan 2017 15:34:45 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Icenowy Zheng <icenowy@...c.xyz>, Rob Herring <robh+dt@...nel.org>,
        Kishon Vijay Abraham I <kishon@...com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bin Liu <b-liu@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-sunxi@...glegroups.com" <linux-sunxi@...glegroups.com>
Subject: Re: [PATCH 1/4] phy: sun4i-usb: support PHY0 on H3 in MUSB mode

On Wed, Jan 18, 2017 at 04:09:32AM +0800, Chen-Yu Tsai wrote:
> Hi,
> 
> On Wed, Jan 18, 2017 at 4:06 AM, Maxime Ripard
> <maxime.ripard@...e-electrons.com> wrote:
> > On Wed, Jan 18, 2017 at 12:57:08AM +0800, Icenowy Zheng wrote:
> >>
> >>
> >> 17.01.2017, 16:06, "Maxime Ripard" <maxime.ripard@...e-electrons.com>:
> >> > 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?

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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