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

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Date:   Wed, 18 Jan 2017 04:09:32 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Icenowy Zheng <icenowy@...c.xyz>, Rob Herring <robh+dt@...nel.org>,
        Chen-Yu Tsai <wens@...e.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

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.

ChenYu

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