linux-kernel - Re: [PATCH] usb: dwc3: core: Don't try to get PHYs during suspend/resume

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Date:   Thu, 11 Jan 2018 11:23:17 +0200
From:   Roger Quadros <rogerq@...com>
To:     Felipe Balbi <balbi@...nel.org>
CC:     <vigneshr@...com>, <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "linux-stable # = v4 . 13" <stable@...r.kernel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: Re: [PATCH] usb: dwc3: core: Don't try to get PHYs during
 suspend/resume



On 11/01/18 11:09, Roger Quadros wrote:
> +Heikki
> 
> On 11/01/18 10:25, Felipe Balbi wrote:
>>
>> Hi,
>>
>> Roger Quadros <rogerq@...com> writes:
>>>>>> -	ret = dwc3_core_soft_reset(dwc);
>>>>>> +	ret = dwc3_core_get_phy(dwc);
>>>>>
>>>>> we can get_phy in dwc3_core_init() as it will get called on resume().
>>>>> This was the $subject of this patch.
>>>>
>>>> indeed. thanks :-)
>>>>
>>>
>>> oops sorry. I meant we can't call dwc3_core_get_phy() in dwc3_core_init(). :P
>>
>> bit of a chicken-and-egg problem. We need to setup the PHY interface
>> before getting the PHYs, but can't get PHY during resume. Maybe the best
>> way here would be to check for the pointers being valid. Something like:
>>
>> if (!phy)
>> 	get_phy();
>>
> 
> OK that should take care of not calling get_phy() on suspend.
> However there is one more issue with the approach
> 
>> @@ -754,15 +754,15 @@ static int dwc3_core_init(struct dwc3 *dwc)
>>  			dwc->maximum_speed = USB_SPEED_HIGH;
>>  	}
>>  
>> -	ret = dwc3_core_get_phy(dwc);
>> +	ret = dwc3_phy_setup(dwc);
>>  	if (ret)
>>  		goto err0;
> 
> here we configure PHY related bits and register the ulpi interface.
> 
>>  
>> -	ret = dwc3_core_soft_reset(dwc);
>> +	ret = dwc3_core_get_phy(dwc);
>>  	if (ret)
>>  		goto err0;
>>  
> 
> we got the PHYs. all OK here.
> 
>> -	ret = dwc3_phy_setup(dwc);
>> +	ret = dwc3_core_soft_reset(dwc);
>>  	if (ret)
>>  		goto err0;
> 
> Now we do a soft reset. This means we loose the PHY configuration bits that we did

Actually I was wrong. We're only resetting the device side (DCTL.CSFTRST) which doesn't seem to affect
GUSB2PHYCFGn and GUSB3PIPECTLn registers.

So we're good.

> in dwc3_phy_setup. So we need to call dwc3_phy_setup again but not re-register the ulpi interface.
> I can use a flag there so that dwc3_ulpi_init() is done only once.
> 

-- 
cheers,
-roger

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