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From:   Peter Chen <hzpeterchen@gmail.com>
Date:   Mon, 29 Jun 2020 15:37:54 +0800
Message-ID: <CAL411-qVjxYk7f+b74XHfj7jpxALS4LYUKe0XdSfwRZcQibNfA@mail.gmail.com>
Subject: Re: [PATCH 1/2] usb: mtu3: disable USB2 LPM
To:     Chunfeng Yun <chunfeng.yun@mediatek.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Felipe Balbi <felipe.balbi@linux.intel.com>,
        USB list <linux-usb@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        linux-mediatek@lists.infradead.org,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Markus Elfring <Markus.Elfring@web.de>,
        linux-arm-kernel@lists.infradead.org
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On Mon, Jun 29, 2020 at 2:04 PM Chunfeng Yun <chunfeng.yun@mediatek.com> wrote:
>
> A SuperSpeed device shall include the USB 2.0 extension descriptor
> and shall support LPM when operating in USB 2.0 HS mode(see usb3.2
> spec9.6.2.1). But we always don't support it, so disable it by
> default, otherwise device will enter LPM suspend mode when
> connected to Win10 system.

Linux also supports USB2 LPM. Besides, USB-IF CH9 test will check
LPM support if the device is USB 2.1, how could you deal with it?

Peter

>
> Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
> ---
>  drivers/usb/mtu3/mtu3_core.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/usb/mtu3/mtu3_core.c b/drivers/usb/mtu3/mtu3_core.c
> index 9dd0216..50d6a40 100644
> --- a/drivers/usb/mtu3/mtu3_core.c
> +++ b/drivers/usb/mtu3/mtu3_core.c
> @@ -604,6 +604,8 @@ static void mtu3_regs_init(struct mtu3 *mtu)
>         mtu3_clrbits(mbase, U3D_MISC_CTRL, VBUS_FRC_EN | VBUS_ON);
>         /* enable automatical HWRW from L1 */
>         mtu3_setbits(mbase, U3D_POWER_MANAGEMENT, LPM_HRWE);
> +       /* always reject LPM request */
> +       mtu3_setbits(mbase, U3D_POWER_MANAGEMENT, LPM_MODE(1));
>
>         /* use new QMU format when HW version >= 0x1003 */
>         if (mtu->gen2cp)
> --
> 1.9.1
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