linux-kernel - Re: [PATCH 2/2] usb: dwc3: drd: Fix lock-up on ID change during system suspend/resume

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Date:   Mon, 12 Feb 2018 12:48:26 +0200
From:   Roger Quadros <rogerq@...com>
To:     Felipe Balbi <balbi@...nel.org>
CC:     <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] usb: dwc3: drd: Fix lock-up on ID change during
 system suspend/resume

Felipe,

On 12/02/18 10:54, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@...com> writes:
>> Adding/removing host/gadget controller before .pm_complete()
>> causes a lock-up. Let's prevent any dual-role state change
>> between .pm_prepare() and .pm_complete() to fix this.
>>
>> Signed-off-by: Roger Quadros <rogerq@...com>
>> ---
>>  drivers/usb/dwc3/core.c | 31 +++++++++++++++++++++++++++++++
>>  drivers/usb/dwc3/core.h |  5 +++++
>>  drivers/usb/dwc3/drd.c  | 10 ++++++----
>>  3 files changed, 42 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> index 42379cc..85388dd 100644
>> --- a/drivers/usb/dwc3/core.c
>> +++ b/drivers/usb/dwc3/core.c
>> @@ -1414,6 +1414,33 @@ static int dwc3_runtime_idle(struct device *dev)
>>  #endif /* CONFIG_PM */
>>  
>>  #ifdef CONFIG_PM_SLEEP
>> +static int dwc3_prepare(struct device *dev)
>> +{
>> +	struct dwc3	*dwc = dev_get_drvdata(dev);
>> +	unsigned long	flags;
>> +
>> +	if (dwc->dr_mode == USB_DR_MODE_OTG) {
>> +		spin_lock_irqsave(&dwc->lock, flags);
>> +		dwc->dr_keep_role = true;
>> +		spin_unlock_irqrestore(&dwc->lock, flags);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static void dwc3_complete(struct device *dev)
>> +{
>> +	struct dwc3	*dwc = dev_get_drvdata(dev);
>> +	unsigned long	flags;
>> +
>> +	if (dwc->dr_mode == USB_DR_MODE_OTG) {
>> +		spin_lock_irqsave(&dwc->lock, flags);
>> +		dwc->dr_keep_role = false;
>> +		spin_unlock_irqrestore(&dwc->lock, flags);
>> +		dwc3_drd_update(dwc);
>> +	}
>> +}
> 
> wouldn't it be far easier to just disable OTG IRQ in prepare? and,
> perhaps, also flush_work_sync() ?
> 

There was some more discussion on this here [1]. Apparently using system_freezable_wq
and a patch mentioned at end of [1] is sufficient as well

[1] https://lkml.org/lkml/2018/1/25/384

Could you please share your view there?

-- 
cheers,
-roger

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