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

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Date:   Fri, 21 Apr 2023 04:21:40 +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 17:39, Sergei Shtylyov wrote:
> On 4/20/23 8:21 PM, Weitao Wang 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.

Best Regards,
Weitao

>> +		return xhci_check_zhaoxin_tier_policy(udev, state);
>>   	else
>>   		return 0;
>>   }
> 
> MBR, Sergey
> .