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

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Message-ID: <54aa1618-63b7-965a-d303-5d35cb554c20@gmail.com>
Date:   Thu, 20 Apr 2023 17:22:17 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     "WeitaoWang-oc@...oxin.com" <WeitaoWang-oc@...oxin.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 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.

[...]
> Best Regards,
> Weitao

MBR, Sergey