linux-kernel - Re: [PATCH 2/3] xhci: Add zhaoxin xHCI U1/U2 feature support

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Date:   Fri, 21 Apr 2023 18:51:26 +0800
From:   "WeitaoWang-oc@...oxin.com" <WeitaoWang-oc@...oxin.com>
To:     Sergei Shtylyov <sergei.shtylyov@...il.com>,
        <gregkh@...uxfoundation.org>, <mathias.nyman@...el.com>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <tonywwang@...oxin.com>, <weitaowang@...oxin.com>
Subject: Re: [PATCH 2/3] xhci: Add zhaoxin xHCI U1/U2 feature support

On 2023/4/20 22:22, Sergei Shtylyov wrote:
> On 4/20/23 11:21 PM, WeitaoWang-oc@...oxin.com wrote:
> 
>>>> Add U1/U2 feature support of xHCI for zhaoxin.
>>>>
>>>> Signed-off-by: Weitao Wang <WeitaoWang-oc@...oxin.com>
>>> [...]
>>>
>>>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
>>>> index 6307bae9cddf..730c0f68518d 100644
>>>> --- a/drivers/usb/host/xhci.c
>>>> +++ b/drivers/usb/host/xhci.c
>>> [...]
>>>> @@ -4938,6 +4938,27 @@ static int xhci_update_timeout_for_interface(struct xhci_hcd *xhci,
>>>>        return 0;
>>>>    }
>>>>    +static int xhci_check_zhaoxin_tier_policy(struct usb_device *udev,
>>>> +        enum usb3_link_state state)
>>>> +{
>>>> +    struct usb_device *parent;
>>>> +    unsigned int num_hubs;
>>>> +
>>>> +    /* Don't enable U1/U2 if the device is on an external hub. */
>>>> +    for (parent = udev->parent, num_hubs = 0; parent->parent;
>>>> +            parent = parent->parent)
>>>> +        num_hubs++;
>>>> +
>>>> +    if (num_hubs < 1)
>>>> +        return 0;
>>>> +
>>>> +    dev_dbg(&udev->dev, "Disabling U1/U2 link state for device"
>>>> +            " below external hub.\n");
>>>> +    dev_dbg(&udev->dev, "Plug device into root hub "
>>>> +            "to decrease power consumption.\n");
>>>
>>>      Please don't break up the message strings.
>>
>> Thanks for your advice, and I will merge this message in next patch version.
>>> [...]
>>>> @@ -4965,6 +4986,8 @@ static int xhci_check_tier_policy(struct xhci_hcd *xhci,
>>>>    {
>>>>        if (xhci->quirks & XHCI_INTEL_HOST)
>>>>            return xhci_check_intel_tier_policy(udev, state);
>>>> +    else if (xhci->quirks & XHCI_ZHAOXIN_HOST)
>>>
>>>      *else* not needed after *return*.
>> This function need a "int" type return value. If remove "else" branch,
>> vendor other than intel and zhaoxin will not get a return value.
> 
>     I didn't tell you to remove the whole branch, just the *else* keyword.

I understand what you mean this time. Here's code needs more concise.
I'll try to do more think and test.Thanks again!

weitao
> [...]
>> Best Regards,
>> Weitao
> 
> MBR, Sergey
> .