linux-kernel - Re: [PATCH v2 00/14] usb: dwc3: meson: add OTG support for GXL/GXM

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Date:   Sun, 29 Mar 2020 13:36:28 +0300
From:   Felipe Balbi <balbi@...nel.org>
To:     Neil Armstrong <narmstrong@...libre.com>, kishon@...com,
        khilman@...libre.com, martin.blumenstingl@...glemail.com
Cc:     Neil Armstrong <narmstrong@...libre.com>,
        linux-amlogic@...ts.infradead.org, linux-usb@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 00/14] usb: dwc3: meson: add OTG support for GXL/GXM


Hi,

Neil Armstrong <narmstrong@...libre.com> writes:
> The USB support was initialy done with a set of PHYs and dwc3-of-simple
> because the architecture of the USB complex was not understood correctly
> at the time (and proper documentation was missing...).
>
> But with the G12A family, the USB complex was correctly understood and
> implemented correctly.
> But seems the G12A architecture was derived for the GXL USB architecture,
> with minor differences and looks we can share most of the USB DWC3 glue
> driver.
>
> This patchset refactors and adds callbacks to handle the architecture
> difference while keeping the main code shared.
>
> The main difference is that on GXL/GXM the USB2 PHY control registers
> are mixed with the PHY registers (we already handle correctly), and
> the GLUE registers are allmost (99%) the same as G12A.
>
> But, the GXL/GXM HW is buggy, here are the quirks :
> - for the DWC2 controller to reset correctly, the GLUE mux must be switched
>   to peripheral when the DWC2 controller probes. For now it's handled by simply
>   switching to device when probing the subnodes, but it may be not enough
> - when manually switching from Host to Device when the USB port is not
>   populated (should not happen with proper Micro-USB/USB-C OTG switch), it
>   makes the DWC3 to crash. The only way to avoid that is to use the Host
>   Disconnect bit to disconnect the DWC3 controller from the port, but we can't
>   recover the Host functionnality unless resetting the DWC3 controller.
>   This bit is set when only manual switch is done, and a warning is printed
>   on manual switching.
>
> The patches 1-9 should be applied first, then either waiting the next release
> or if the usb maintainer can provide us a stable tag, we can use it to merge
> the DT and bindings.
>
> Changes since v1 at [1]:
> - Fixed DT bindings to take in account usb2-phy2 on GXM
> - Added comment in patch2
> - Fixed patch 5 and moved fix out
> - Collected tags
> - Lower DT patch changes, switch p20x-q20x port B as OTG by default

patches 1-6 are applied to my testing/next

-- 
balbi

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