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Date:   Tue, 23 Mar 2021 16:31:29 +0100
From:   Greg KH <gregkh@linuxfoundation.org>
To:     =?utf-8?B?5ZGo55Cw5p2wIChaaG91IFlhbmppZSk=?= 
        <zhouyanjie@wanyeetech.com>
Cc:     hminas@synopsys.com, paul@crapouillou.net,
        linux-mips@vger.kernel.org, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, dongsheng.qiu@ingenic.com,
        aric.pzqi@ingenic.com, sernia.zhou@foxmail.com,
        Dragan =?utf-8?B?xIxlxI1hdmFj?= <dragancecavac@yahoo.com>
Subject: Re: [PATCH] USB: DWC2: Add VBUS overcurrent detection control.
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References: <1616513066-62025-1-git-send-email-zhouyanjie@wanyeetech.com>
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On Tue, Mar 23, 2021 at 11:24:26PM +0800, 周琰杰 (Zhou Yanjie) wrote:
> Introduce configurable option for enabling GOTGCTL register
> bits VbvalidOvEn and VbvalidOvVal. Once selected it disables
> VBUS overcurrent detection.
> 
> This patch is derived from Dragan Čečavac (in the kernel 3.18
> tree of CI20). It is very useful for the MIPS Creator CI20(r1).
> Without this patch, CI20's OTG port has a great probability to
> face overcurrent warning, which breaks the OTG functionality.
> 
> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
> Signed-off-by: Dragan Čečavac <dragancecavac@yahoo.com>
> ---
>  drivers/usb/dwc2/Kconfig | 6 ++++++
>  drivers/usb/dwc2/core.c  | 9 +++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/drivers/usb/dwc2/Kconfig b/drivers/usb/dwc2/Kconfig
> index c131719..e40d187 100644
> --- a/drivers/usb/dwc2/Kconfig
> +++ b/drivers/usb/dwc2/Kconfig
> @@ -94,4 +94,10 @@ config USB_DWC2_DEBUG_PERIODIC
>  	  non-periodic transfers, but of course the debug logs will be
>  	  incomplete. Note that this also disables some debug messages
>  	  for which the transfer type cannot be deduced.
> +
> +config USB_DWC2_DISABLE_VOD
> +	bool "Disable VBUS overcurrent detection"
> +	help
> +	  Say Y here to switch off VBUS overcurrent detection. It enables USB
> +	  functionality blocked by overcurrent detection.

Why would this be a configuration option?  Shouldn't this be dynamic and
just work properly automatically?

You should not have to do this on a build-time basis, it should be able
to be detected and handled properly at run-time for all devices.

If you know this is needed for a specific type of device, detect it and
make the change then, otherwise this could break working systems, right?

thanks,

greg k-h