linux-kernel - Re: [PATCH] usb: mtu3: fix USB 3.0 dual-role-switch from device to host

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Message-ID: <37276fd01a518dadff57ef66c7971b78baa9dc15.camel@mediatek.com>
Date:   Wed, 20 Apr 2022 17:18:38 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Macpaul Lin <macpaul.lin@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
CC:     Miles Chen <miles.chen@...iatek.com>,
        Bear Wang <bear.wang@...iatek.com>,
        Pablo Sun <pablo.sun@...iatek.com>,
        Fabien Parent <fparent@...libre.com>,
        Mediatek WSD Upstream <wsd_upstream@...iatek.com>,
        Macpaul Lin <macpaul@...il.com>, <stable@...r.kernel.org>,
        Tainping Fang <tianping.fang@...iatek.com>
Subject: Re: [PATCH] usb: mtu3: fix USB 3.0 dual-role-switch from device to
 host

On Tue, 2022-04-19 at 16:12 +0800, Macpaul Lin wrote:
> Issue description:
>   When an OTG port has been switched to device role and then switch
> back
>   to host role again, the USB 3.0 Host (XHCI) will not be able to
> detect
>   "plug in event of a connected USB 2.0/1.0 ((Highspeed and
> Fullspeed)
>   devices until system reboot.
> 
> Root cause and Solution:
>   There is a condition checking flag "ssusb->otg_switch.is_u3_drd" in
>   toggle_opstate(). At the end of role switch procedure,
> toggle_opstate()
>   will be called to set DC_SESSION and SOFT_CONN bit. If "is_u3_drd"
> was
>   set and switched the role to USB host 3.0, bit DC_SESSION and
> SOFT_CONN
>   will be skipped hence caused the port cannot detect connected USB
> 2.0
>   (Highspeed and Fullspeed) devices. Simply remove the condition
> check to
>   solve this issue.
> 
> Fixes: d0ed062a8b75 ("usb: mtu3: dual-role mode support")
> Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
> Signed-off-by: Tainping Fang <tianping.fang@...iatek.com>
> Tested-by: Fabien Parent <fparent@...libre.com>
> Cc: stable@...r.kernel.org
> ---
>  drivers/usb/mtu3/mtu3_dr.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/usb/mtu3/mtu3_dr.c b/drivers/usb/mtu3/mtu3_dr.c
> index ec6ec621838b..b820724c56e4 100644
> --- a/drivers/usb/mtu3/mtu3_dr.c
> +++ b/drivers/usb/mtu3/mtu3_dr.c
> @@ -21,10 +21,8 @@ static inline struct ssusb_mtk
> *otg_sx_to_ssusb(struct otg_switch_mtk *otg_sx)
>  
>  static void toggle_opstate(struct ssusb_mtk *ssusb)
>  {
> -	if (!ssusb->otg_switch.is_u3_drd) {
> -		mtu3_setbits(ssusb->mac_base, U3D_DEVICE_CONTROL,
> DC_SESSION);
> -		mtu3_setbits(ssusb->mac_base, U3D_POWER_MANAGEMENT,
> SOFT_CONN);
> -	}
> +	mtu3_setbits(ssusb->mac_base, U3D_DEVICE_CONTROL, DC_SESSION);
> +	mtu3_setbits(ssusb->mac_base, U3D_POWER_MANAGEMENT, SOFT_CONN);
>  }
>  
Reviewed-by: Chunfeng Yun <chunfeng.yun@...iatek.com>

Thanks

>  /* only port0 supports dual-role mode */