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 11:09:54 +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

+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
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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