linux-kernel - Re: [linux-next][PATCH] usb: dwc3: omap: remove IRQ

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Date:   Mon, 3 Jul 2017 09:57:17 +0530
From:   Vignesh R <vigneshr@...com>
To:     "Strashko, Grygorii" <grygorii.strashko@...com>,
        Tony Lindgren <tony@...mide.com>
CC:     "GregKroah-Hartmangregkh@...uxfoundation.org" 
        <GregKroah-Hartmangregkh@...uxfoundation.org>,
        Felipe Balbi <balbi@...nel.org>,
        "linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Nori, Sekhar" <nsekhar@...com>
Subject: Re: [linux-next][PATCH] usb: dwc3: omap: remove IRQ_NOAUTOEN used
 with shared irq

Hi,

On Saturday 01 July 2017 01:04 AM, Strashko, Grygorii wrote:
> 
> 
> On 06/29/2017 01:03 AM, Tony Lindgren wrote:
>> * Vignesh R <vigneshr@...com> [170628 21:21]:
>>>
>>>
>>> On Thursday 29 June 2017 05:01 AM, Strashko, Grygorii wrote:
>>>> IRQ_NOAUTOEN can't be used with shared IRQs and Kernel now will triggers
>>>> warning if it happns, since commit 04c848d39879 ("genirq: Warn when
>>>> IRQ_NOAUTOEN is used with shared interrupts"). And this is the case for
>>>> OMAP DWC 3 driver.
>>>>
>>>> Hence, remove IRQ_NOAUTOEN flag and instead call disable_irq() before
>>>> disabling PM runtime in probe error path handling.
>>>
>>> Or, how about requesting the irq at the end of probe after extcon
>>> registration?
>>
>> Hmm yeah, what prevents the issue that we tried to fix with commit
>> 12a7f17fac5b ("usb: dwc3: omap: fix race of pm runtime with irq handler
>> in probe")?
> 
> No, I think. There should be the disable_irq() call any way
> before pm_runtime_put_sync(dev);| pm_runtime_disable(dev); -
> once IRQ is requested driver can't know if IRQ handler is running now or not
> unless it will call disable_irq()/free_irq().
> 
> But, I've also thought about moving request_irq() down (seems
> it can be moved even after of_platform_populate()).
> looks like it can be separate patch.
> 

commit 12a7f17fac5b says PM runtime can race with IRQ handler when
deferred probing happening due to extcon, therefore IRQ_NOAUTOEN was set
and disable_irq() call was added. If IRQ handler registration is moved
to a place after of_platform_populate(), then we can be sure that extcon
is registered and there wont be any deferred probe or race with irq
handler and PM runtime. Would disable_irq() still be needed then?

> 
>>>> Fixes: 12a7f17fac5b ("usb: dwc3: omap: fix race of pm runtime with...")
>>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>>>> ---
>>>>   drivers/usb/dwc3/dwc3-omap.c | 3 +--
>>>>   1 file changed, 1 insertion(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/dwc3/dwc3-omap.c b/drivers/usb/dwc3/dwc3-omap.c
>>>> index 9892650..cd9bef5 100644
>>>> --- a/drivers/usb/dwc3/dwc3-omap.c
>>>> +++ b/drivers/usb/dwc3/dwc3-omap.c
>>>> @@ -512,7 +512,6 @@ static int dwc3_omap_probe(struct platform_device *pdev)
>>>>   
>>>>   	/* check the DMA Status */
>>>>   	reg = dwc3_omap_readl(omap->base, USBOTGSS_SYSCONFIG);
>>>> -	irq_set_status_flags(omap->irq, IRQ_NOAUTOEN);
>>>>   	ret = devm_request_threaded_irq(dev, omap->irq, dwc3_omap_interrupt,
>>>>   					dwc3_omap_interrupt_thread, IRQF_SHARED,
>>>>   					"dwc3-omap", omap);
>>>> @@ -533,10 +532,10 @@ static int dwc3_omap_probe(struct platform_device *pdev)
>>>>   	}
>>>>   
>>>>   	dwc3_omap_enable_irqs(omap);
>>>> -	enable_irq(omap->irq);
>>>>   	return 0;
>>>>   
>>>>   err1:
>>>> +	disable_irq(omap->irq);
>>>>   	pm_runtime_put_sync(dev);
>>>>   	pm_runtime_disable(dev);
>>>>   
> 

-- 
Regards
Vignesh