linux-kernel - Re: [PATCH] usb: cdns3: gadget: Fix g_audio use case when connected to Super-Speed host

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Date:   Wed, 30 Oct 2019 10:44:10 +0200
From:   Roger Quadros <rogerq@...com>
To:     Peter Chen <peter.chen@....com>
CC:     "felipe.balbi@...ux.intel.com" <felipe.balbi@...ux.intel.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "pawell@...ence.com" <pawell@...ence.com>,
        "nsekhar@...com" <nsekhar@...com>,
        "kurahul@...ence.com" <kurahul@...ence.com>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] usb: cdns3: gadget: Fix g_audio use case when connected
 to Super-Speed host



On 30/10/2019 08:36, Peter Chen wrote:
> On 19-10-29 17:15:14, Roger Quadros wrote:
>> Take into account gadget driver's speed limit when programming
>> controller speed.
>>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>> Hi Greg,
>>
>> Please apply this for -rc.
>> Without this, g_audio is broken on cdns3 USB controller is
>> connected to a Super-Speed host.
>>
>> cheers,
>> -roger
>>
>>   drivers/usb/cdns3/gadget.c | 31 ++++++++++++++++++++++++++-----
>>   1 file changed, 26 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/usb/cdns3/gadget.c b/drivers/usb/cdns3/gadget.c
>> index 40dad4e8d0dc..1c724c20d468 100644
>> --- a/drivers/usb/cdns3/gadget.c
>> +++ b/drivers/usb/cdns3/gadget.c
>> @@ -2338,9 +2338,35 @@ static int cdns3_gadget_udc_start(struct usb_gadget *gadget,
>>   {
>>   	struct cdns3_device *priv_dev = gadget_to_cdns3_device(gadget);
>>   	unsigned long flags;
>> +	enum usb_device_speed max_speed = driver->max_speed;
>>   
>>   	spin_lock_irqsave(&priv_dev->lock, flags);
>>   	priv_dev->gadget_driver = driver;
>> +
>> +	/* limit speed if necessary */
>> +	max_speed = min(driver->max_speed, gadget->max_speed);
>> +
>> +	switch (max_speed) {
>> +	case USB_SPEED_FULL:
>> +		writel(USB_CONF_SFORCE_FS, &priv_dev->regs->usb_conf);
>> +		writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
>> +		break;
>> +	case USB_SPEED_HIGH:
>> +		writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
>> +		break;
>> +	case USB_SPEED_SUPER:
>> +		break;
>> +	default:
>> +		dev_err(priv_dev->dev,
>> +			"invalid maximum_speed parameter %d\n",
>> +			max_speed);
>> +		/* fall through */
>> +	case USB_SPEED_UNKNOWN:
>> +		/* default to superspeed */
>> +		max_speed = USB_SPEED_SUPER;
>> +		break;
>> +	}
>> +
>>   	cdns3_gadget_config(priv_dev);
>>   	spin_unlock_irqrestore(&priv_dev->lock, flags);
>>   	return 0;
>> @@ -2570,12 +2596,7 @@ static int cdns3_gadget_start(struct cdns3 *cdns)
>>   	/* Check the maximum_speed parameter */
>>   	switch (max_speed) {
>>   	case USB_SPEED_FULL:
>> -		writel(USB_CONF_SFORCE_FS, &priv_dev->regs->usb_conf);
>> -		writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
>> -		break;
>>   	case USB_SPEED_HIGH:
>> -		writel(USB_CONF_USB3DIS, &priv_dev->regs->usb_conf);
>> -		break;
>>   	case USB_SPEED_SUPER:
>>   		break;
>>   	default:
> 
> Just a small comment:
> 
> You could delete switch-case at cdns3_gadget_start, and just use
> if() statement, eg:
> 
> 	max_speed = usb_get_maximum_speed(cdns->dev);
> 	if (max_speed == USB_SPEED_UNKNOWN)
> 		max_speed = USB_SPEED_SUPER;

But then it will not take care of bailing out for USB_SPEED_WIRELESS,
USB_SPEED_SUPER_PLUS and any future speeds.

> 
> Otherwise:
> 
> Acked-by: Peter Chen <peter.chen@....com>
> 

-- 
cheers,
-roger

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