linux-kernel - Re: [PATCH] usb: mtu3: Don't check the USB3 status bits if the max speed is USB2

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Date:   Thu, 4 May 2023 07:48:34 +0000
From:   Chunfeng Yun (云春峰) 
        <Chunfeng.Yun@...iatek.com>
To:     "amergnat@...libre.com" <amergnat@...libre.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "fparent@...libre.com" <fparent@...libre.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "abailon@...libre.com" <abailon@...libre.com>
Subject: Re: [PATCH] usb: mtu3: Don't check the USB3 status bits if the max
 speed is USB2

On Wed, 2023-04-26 at 21:24 +0200, amergnat@...libre.com wrote:
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> 
> 
> From: Alexandre Bailon <abailon@...libre.com>
> 
> If the IP is U3, the driver will check some USB3 status bits.
> This could fail if only USB2 is used.
> This only check these bits if USB operate at USB3 speed.
> 
> Signed-off-by: Alexandre Bailon <abailon@...libre.com>
> Signed-off-by: Fabien Parent <fparent@...libre.com>
> Signed-off-by: Alexandre Mergnat <amergnat@...libre.com>
> ---
> This patch is ported from downstream. Without this fix, USB doesn't
> work if USB2 protocol is used first.
> ---
>  drivers/usb/mtu3/mtu3_core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/mtu3/mtu3_core.c
> b/drivers/usb/mtu3/mtu3_core.c
> index a3a6282893d0..00dba871aff8 100644
> --- a/drivers/usb/mtu3/mtu3_core.c
> +++ b/drivers/usb/mtu3/mtu3_core.c
> @@ -100,7 +100,7 @@ static int mtu3_device_enable(struct mtu3 *mtu)
> 
>         mtu3_clrbits(ibase, U3D_SSUSB_IP_PW_CTRL2, SSUSB_IP_DEV_PDN);
> 
> -       if (mtu->u3_capable) {
> +       if (mtu->u3_capable && mtu->max_speed >= USB_SPEED_SUPER) {
NAK

Maybe you misunderstand the usage of @u3_capable, if you only use u2
function but the controller support u3 function, shall disable u3 by  
property "mediatek,u3p-dis-msk", then no need check speed here.

Thanks

>                 check_clk = SSUSB_U3_MAC_RST_B_STS;
>                 mtu3_clrbits(ibase, SSUSB_U3_CTRL(0),
>                         (SSUSB_U3_PORT_DIS | SSUSB_U3_PORT_PDN |
> 
> ---
> base-commit: fe15c26ee26efa11741a7b632e9f23b01aca4cc6
> change-id: 20230426-usb-mtu3-improvement-77d987def9fe
> 
> Best regards,
> --
> Alexandre Mergnat <amergnat@...libre.com>
>