Re: [PATCH] usb: dwc2: Revert "usb: dwc2: Disable all EP's on disconnect"

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Hi Dan,

On 12/7/2018 2:16 PM, Dan Carpenter wrote:
> On Wed, Dec 05, 2018 at 12:52:22PM +0000, Minas Harutyunyan wrote:
>> Hi,
>>
>> On 12/4/2018 5:29 PM, Dan Carpenter wrote:
>>> On Tue, Dec 04, 2018 at 12:34:08PM +0000, Minas Harutyunyan wrote:
>>>> @@ -3185,12 +3183,13 @@ void dwc2_hsotg_disconnect(struct dwc2_hsotg *hsotg)
>>>>            hsotg->connected = 0;
>>>>            hsotg->test_mode = 0;
>>>>
>>>> -       /* all endpoints should be shutdown */
>>>>            for (ep = 0; ep < hsotg->num_of_eps; ep++) {
>>>>                    if (hsotg->eps_in[ep])
>>>> -                       dwc2_hsotg_ep_disable(&hsotg->eps_in[ep]->ep);
>>>> +                       kill_all_requests(hsotg, hsotg->eps_in[ep],
>>>> +                                                         -ESHUTDOWN);
>>>>                    if (hsotg->eps_out[ep])
>>>> -                       dwc2_hsotg_ep_disable(&hsotg->eps_out[ep]->ep);
>>>> +                       kill_all_requests(hsotg, hsotg->eps_out[ep],
>>>> +                                                         -ESHUTDOWN);
>>>
>>>
>>> Should this part be in a separate patch?
>>>
>>> I'm not trying to be rhetorical at all.  I literally don't know the
>>> code very well.  Hopefully the full commit message will explain it.
>>>
>>
>> Actually, this fragment of patch revert changes from V2 and keep
>> untouched dwc2_hsotg_disconnect() function.
>>
> 
> To me it feels like there are two issues.  The first is this change, and
> the second is fixing the lockdep warning.
> 
> 
>>>>            }
>>>>
>>>>            call_gadget(hsotg, disconnect);
>>>> @@ -3234,6 +3233,8 @@ static void dwc2_hsotg_irq_fifoempty(struct
>>>> dwc2_hsotg *hsotg, bool periodic)
>>>>                            GINTSTS_PTXFEMP |  \
>>>>                            GINTSTS_RXFLVL)
>>>>
>>>> +static int dwc2_hsotg_ep_disable(struct usb_ep *ep);
>>>> +
>>>>     /**
>>>>      * dwc2_hsotg_core_init - issue softreset to the core
>>>>      * @hsotg: The device state
>>>> @@ -3258,12 +3259,14 @@ void dwc2_hsotg_core_init_disconnected(struct
>>>> dwc2_hsotg *hsotg,
>>>>                            return;
>>>>            } else {
>>>>                    /* all endpoints should be shutdown */
>>>> +               spin_unlock(&hsotg->lock);
>>>>                    for (ep = 1; ep < hsotg->num_of_eps; ep++) {
>>>>                            if (hsotg->eps_in[ep])
>>>>    
>>>> dwc2_hsotg_ep_disable(&hsotg->eps_in[ep]->ep);
>>>>                            if (hsotg->eps_out[ep])
>>>>    
>>>> dwc2_hsotg_ep_disable(&hsotg->eps_out[ep]->ep);
>>>>                    }
>>>> +               spin_lock(&hsotg->lock);
>>>>            }
>>>>
>>>>            /*
>>>
>>> The idea here is that this is the only caller which is holding the
>>> lock and we drop it here and take it again inside dwc2_hsotg_ep_disable().
>>> I don't know the code very well and can't totally swear that this
>>> doesn't introduce a small race condition...
>>>
>> Above fragment of patch allow to keep untouched dwc2_hsotg_ep_disble()
>> function also, without changing spin_lock/_unlock stuff inside function.
>>
>> My approach here minimally update code to add any races. Just in
>> dwc2_hsotg_core_init_disconnected() function on USB reset interrupt
>> perform disabling all EP's. Because on USB reset interrupt, called from interrupt
>> handler with acquired lock and dwc2_hsotg_ep_disble() function (without
>> changes) acquire lock, just need to unlock lock to avoid any troubles.
>>
> 
> Yes.  I understand that.  I just don't like it.
> 
> Although your patch is more "minimal" in that it touches fewer lines of
> code it's actually more complicated because we have to verify that it's
> safe to drop the lock.
> 
> 
>>> Another option would be to introduce a new function which takes the lock
>>> and change all the other callers instead.  To me that would be easier to
>>> review...  See below for how it might look:
>>>
>>> regards,
>>> dan carpenter
>>>
>>> diff --git a/drivers/usb/dwc2/gadget.c b/drivers/usb/dwc2/gadget.c
>>> index 94f3ba995580..b17a5dbefd5f 100644
>>> --- a/drivers/usb/dwc2/gadget.c
>>> +++ b/drivers/usb/dwc2/gadget.c
>>> @@ -3166,6 +3166,7 @@ static void kill_all_requests(struct dwc2_hsotg *hsotg,
>>>    }
>>>    
>>>    static int dwc2_hsotg_ep_disable(struct usb_ep *ep);
>>> +static int dwc2_hsotg_ep_disable_lock(struct usb_ep *ep);
>>>    
>>>    /**
>>>     * dwc2_hsotg_disconnect - disconnect service
>>> @@ -3188,9 +3189,9 @@ void dwc2_hsotg_disconnect(struct dwc2_hsotg *hsotg)
>>>    	/* all endpoints should be shutdown */
>>>    	for (ep = 0; ep < hsotg->num_of_eps; ep++) {
>>>    		if (hsotg->eps_in[ep])
>>> -			dwc2_hsotg_ep_disable(&hsotg->eps_in[ep]->ep);
>>> +			dwc2_hsotg_ep_disable_lock(&hsotg->eps_in[ep]->ep);
>>>    		if (hsotg->eps_out[ep])
>>> -			dwc2_hsotg_ep_disable(&hsotg->eps_out[ep]->ep);
>>> +			dwc2_hsotg_ep_disable_lock(&hsotg->eps_out[ep]->ep);
>>>    	}
>>>    
>>>    	call_gadget(hsotg, disconnect);
>>> @@ -4069,10 +4070,8 @@ static int dwc2_hsotg_ep_disable(struct usb_ep *ep)
>>>    	struct dwc2_hsotg *hsotg = hs_ep->parent;
>>>    	int dir_in = hs_ep->dir_in;
>>>    	int index = hs_ep->index;
>>> -	unsigned long flags;
>>>    	u32 epctrl_reg;
>>>    	u32 ctrl;
>>> -	int locked;
>>>    
>>>    	dev_dbg(hsotg->dev, "%s(ep %p)\n", __func__, ep);
>>>    
>>> @@ -4088,10 +4087,6 @@ static int dwc2_hsotg_ep_disable(struct usb_ep *ep)
>>>    
>>>    	epctrl_reg = dir_in ? DIEPCTL(index) : DOEPCTL(index);
>>>    
>>> -	locked = spin_is_locked(&hsotg->lock);
>>> -	if (!locked)
>>> -		spin_lock_irqsave(&hsotg->lock, flags);
>>> -
>>>    	ctrl = dwc2_readl(hsotg, epctrl_reg);
>>>    
>>>    	if (ctrl & DXEPCTL_EPENA)
>>> @@ -4114,12 +4109,23 @@ static int dwc2_hsotg_ep_disable(struct usb_ep *ep)
>>>    	hs_ep->fifo_index = 0;
>>>    	hs_ep->fifo_size = 0;
>>>    
>>> -	if (!locked)
>>> -		spin_unlock_irqrestore(&hsotg->lock, flags);
>>> -
>>>    	return 0;
>>>    }
>>>    
>>> +static int dwc2_hsotg_ep_disable_lock(struct usb_ep *ep)
>>> +{
>>> +	struct dwc2_hsotg_ep *hs_ep = our_ep(ep);
>>> +	struct dwc2_hsotg *hsotg = hs_ep->parent;
>>> +	unsigned long flags;
>>> +	int ret;
>>> +
>>> +	spin_lock_irqsave(&hsotg->lock, flags);
>>> +	ret = dwc2_hsotg_ep_disable(ep);
>>> +	spin_unlock_irqrestore(&hsotg->lock, flags);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>>    /**
>>>     * on_list - check request is on the given endpoint
>>>     * @ep: The endpoint to check.
>>> @@ -4267,7 +4273,7 @@ static int dwc2_hsotg_ep_sethalt_lock(struct usb_ep *ep, int value)
>>>    
>>>    static const struct usb_ep_ops dwc2_hsotg_ep_ops = {
>>>    	.enable		= dwc2_hsotg_ep_enable,
>>> -	.disable	= dwc2_hsotg_ep_disable,
>>> +	.disable	= dwc2_hsotg_ep_disable_lock,
>>>    	.alloc_request	= dwc2_hsotg_ep_alloc_request,
>>>    	.free_request	= dwc2_hsotg_ep_free_request,
>>>    	.queue		= dwc2_hsotg_ep_queue_lock,
>>> @@ -4407,9 +4413,9 @@ static int dwc2_hsotg_udc_stop(struct usb_gadget *gadget)
>>>    	/* all endpoints should be shutdown */
>>>    	for (ep = 1; ep < hsotg->num_of_eps; ep++) {
>>>    		if (hsotg->eps_in[ep])
>>> -			dwc2_hsotg_ep_disable(&hsotg->eps_in[ep]->ep);
>>> +			dwc2_hsotg_ep_disable_lock(&hsotg->eps_in[ep]->ep);
>>>    		if (hsotg->eps_out[ep])
>>> -			dwc2_hsotg_ep_disable(&hsotg->eps_out[ep]->ep);
>>> +			dwc2_hsotg_ep_disable_lock(&hsotg->eps_out[ep]->ep);
>>>    	}
>>>    
>>>    	spin_lock_irqsave(&hsotg->lock, flags);
>>> @@ -4857,9 +4863,9 @@ int dwc2_hsotg_suspend(struct dwc2_hsotg *hsotg)
>>>    
>>>    		for (ep = 0; ep < hsotg->num_of_eps; ep++) {
>>>    			if (hsotg->eps_in[ep])
>>> -				dwc2_hsotg_ep_disable(&hsotg->eps_in[ep]->ep);
>>> +				dwc2_hsotg_ep_disable_lock(&hsotg->eps_in[ep]->ep);
>>>    			if (hsotg->eps_out[ep])
>>> -				dwc2_hsotg_ep_disable(&hsotg->eps_out[ep]->ep);
>>> +				dwc2_hsotg_ep_disable_lock(&hsotg->eps_out[ep]->ep);
>>>    		}
>>>    	}
>>>    
>>>
>>
>> Your code doesn't take care about fifo_map warnings from
>> dwc2_hsotg_init_fifo() function. Before calling dwc2_hsotg_init_fifo()
>> from dwc2_hsotg_core_init_disconnected() function all Ep's should
>> disabled and fifo bitmap should be cleared.
>>
> 
> Correct.  I am only trying to fix the locking.  I hope you can fix the
> rest in a separate patch.
> 
Yeah. I'll try deeper investigate driver locking flow and fix it later. 
Actually, I like your idea with introducing dwc2_hsotg_ep_disable_lock() 
function. Maybe you yourself will submit new patch for safe locking 
fixes? But please just after my patch will applied :-)
Currently there are 2-3 high priority issues reported by community and I 
should find solutions/fixes.
Thank you very much for your time and useful feedback.

Thanks,
Minas


> regards,
> dan carpenter
> 
> 





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