linux-kernel - Re: [PATCH v1 0/3] usb: dwc3: Avoid using reserved EPs

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Message-ID: <20250116231835.isbwmq5yz5issy3w@synopsys.com>
Date: Thu, 16 Jan 2025 23:18:45 +0000
From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>, Ferry Toth <fntoth@...il.com>
Subject: Re: [PATCH v1 0/3] usb: dwc3: Avoid using reserved EPs

On Thu, Jan 16, 2025, Andy Shevchenko wrote:
> On some platforms (Intel-based and AFAIK ARM-based) the EPs in the gadget
> (USB Device Controller mode) may be reserved for some special means, such as
> tracing. This series extends DT schema and driver to avoid using those.
> Without this the USB gadget mode won't work properly (those devices that
> "luckily" allocated the reserved EPs).
> 
> Ferry already tested the privately sent PoC of this, but I ask him again to
> re-test this version which is slightly different.
> 
> Andy Shevchenko (3):
>   dt-bindings: usb: dwc3: Add a property to reserve endpoints
>   usb: dwc3: gadget: Add support for snps,reserved-endpoints property
>   usb: dwc3: gadget: Skip endpoints ep[18]{in,out} on Intel Merrifield
> 
>  .../devicetree/bindings/usb/snps,dwc3.yaml    | 10 +++++
>  drivers/usb/dwc3/dwc3-pci.c                   |  9 +++++
>  drivers/usb/dwc3/gadget.c                     | 38 ++++++++++++++++++-
>  3 files changed, 56 insertions(+), 1 deletion(-)
> 
> -- 
> 2.43.0.rc1.1336.g36b5255a03ac
> 

I'm not entirely clear on the reason for this change yet.

How would this even work without dwc3 managing these endpoints (all the
init/teardown/fifo allocation/start/stop flow). Can you provide more
info on this hardware?

Thanks,
Thinh