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

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Message-ID: <610c35d0-31b9-0c51-81e4-9f0d1daf5c51@ti.com>
Date:   Wed, 10 Jan 2018 16:13:02 +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>
Subject: Re: [PATCH] usb: dwc3: core: Don't try to get PHYs during
 suspend/resume



On 10/01/18 16:04, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@...com> writes:
>>> Roger Quadros <rogerq@...com> writes:
>>>> Felipe,
>>>>
>>>> On 10/01/18 15:11, Roger Quadros wrote:
>>>>> The USB PHYs should be requested only once during the life cycle of
>>>>> this driver.
>>>>>
>>>>> As dwc3_core_init() is called during system suspend/resume
>>>>> it will result in multiple calls to dwc3_core_get_phy() which is wrong.
>>>>>
>>>>> To prevent that let's move dwc3_core_get_phy() call
>>>>> outside dwc3_core_init().
>>>>>
>>>>> Fixes: 541768b08a4 ("usb: dwc3: core: Call dwc3_core_get_phy() before initializing phys")
>>>>> Cc: linux-stable <stable@...r.kernel.org> # >= v4.13
>>>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>>>
>>>> FYI. this patch brings the code back to
>>>> revert 541768b08a40	("usb: dwc3: core: Call dwc3_core_get_phy() before initializing phys")
>>>> revert f54edb539c11	("usb: dwc3: core: initialize ULPI before trying to get the PHY")
>>>>
>>>> So looks like this will break ULPI PHY case?
>>>>
>>>> Where do we initialize ULPI PHY, in dwc3_phy_setup()?
>>>>
>>>> if so then 541768b08a40 breaks the ULPI PHY case as well, right?
>>>
>>> indeed, that commit regressed ULPI PHYs :-(
>>>
>>> Seems like it should be more like below:
>>>
>>> @@ -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);
>>
>> But can we do a dwc3_phy_setup() without doing the soft reset of the controller first?
> 
> as long as clocks are running, we can do that, yes.
> 
>>> -	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

-- 
cheers,
-roger

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