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

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Message-ID: <327eac7d-80e2-bbd6-4fb4-98d947335698@ti.com>
Date:   Wed, 10 Jan 2018 15:56:50 +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 15:33, Felipe Balbi wrote:
> 
> Hi,
> 
> 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?


>  	if (ret)
>  		goto err0;
>  
> -	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.

>  	if (ret)
>  		goto err0;
>  
> -	ret = dwc3_phy_setup(dwc);
> +	ret = dwc3_core_soft_reset(dwc);
>  	if (ret)
>  		goto err0;
>  
> And maybe we rename dwc3_phy_setup() to dwc3_phy_intf_config() just to
> make the name match what the function actually does. Can you check that
> it won't regress the case reported by Carlos? If that works, then we
> would have to move BOTH dwc3_phy_setup() (dwc3_phy_intf_config()) and
> dwc3_core_get_phy() outside of dwc3_core_init(), which would mean
> duplicated code in suspend/resume handlers.
> 
> I'm sure we can sort that out in another way; but the proper order is:
> 
> -> initialize ULPI (if necessary)
> -> get phy
> -> soft reset
> 

-- 
cheers,
-roger

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