linux-kernel - Re: [PATCH] mfd: mt6397: irq domain should initialize before mfd_add

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Message-ID: <20160407075214.GX3323@x1>
Date:	Thu, 7 Apr 2016 08:52:14 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Henry Chen <henryc.chen@...iatek.com>
Cc:	John Crispin <blogic@...nwrt.org>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	linux-kernel@...r.kernel.org, Flora Fu <flora.fu@...iatek.com>,
	linux-mediatek@...ts.infradead.org, linux@...ck-us.net,
	Matthias Brugger <matthias.bgg@...il.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] mfd: mt6397: irq domain should initialize before
 mfd_add_devices()

On Wed, 06 Apr 2016, Henry Chen wrote:

> On Thu, 2016-03-31 at 16:07 +0200, John Crispin wrote:
> > 
> > On 31/03/2016 15:41, Yingjoe Chen wrote:
> > > On Thu, 2016-03-31 at 11:08 +0200, John Crispin wrote:
> > >>
> > >> On 31/03/2016 04:32, Yingjoe Chen wrote:
> > >>> On Thu, 2016-03-31 at 09:40 +0800, Henry Chen wrote:
> > >>>> On Wed, 2016-03-30 at 11:18 +0200, John Crispin wrote:
> > >>>>> Hi,
> > >>>>>
> > >>>>> small nitpick inline
> > >>>>>
> > >>>>> On 30/03/2016 09:25, Henry Chen wrote:
> > >>>>>> Some sub driver like RTC module need irq domain from parent to create
> > >>>>>> irq mapping when driver initialize. so move mt6397_irq_init() before
> > >>>>>> mfd_add_devices().
> > >>>>>>
> > >>>>>> Signed-off-by: Henry Chen <henryc.chen@...iatek.com>
> > >>>>>> ---
> > >>>>>> This patch fixed the below warning based on "Linux kernel v4.6-rc1"
> > >>>>>> WARNING: CPU: 1 PID: 132 at kernel/mediatek/kernel/irq/irqdomain.c:471
> > >>>>>> irq_create_mapping+0xc4/0xd0
> > >>>>>> ---
> > >>>>>>  drivers/mfd/mt6397-core.c | 37 ++++++++++++++++++++++---------------
> > >>>>>>  1 file changed, 22 insertions(+), 15 deletions(-)
> > >>>>>>
> > >>>>>> diff --git a/drivers/mfd/mt6397-core.c b/drivers/mfd/mt6397-core.c
> > >>>>>> index 8e8d932..a879223 100644
> > >>>>>> --- a/drivers/mfd/mt6397-core.c
> > >>>>>> +++ b/drivers/mfd/mt6397-core.c
> > >>>>>> @@ -270,22 +270,36 @@ static int mt6397_probe(struct platform_device *pdev)
> > >>>>>>  		goto fail_irq;
> > >>>>>>  	}
> > >>>>>>  
> > >>>>>> +	pmic->irq = platform_get_irq(pdev, 0);
> > >>>>>> +
> > >>>>>>  	switch (id & 0xff) {
> > >>>>>>  	case MT6323_CID_CODE:
> > >>>>>> -		pmic->int_con[0] = MT6323_INT_CON0;
> > >>>>>> -		pmic->int_con[1] = MT6323_INT_CON1;
> > >>>>>> -		pmic->int_status[0] = MT6323_INT_STATUS0;
> > >>>>>> -		pmic->int_status[1] = MT6323_INT_STATUS1;
> > >>>>>> +		if (pmic->irq > 0) {
> > >>>>>
> > >>>>> should this not be
> > >>>>>
> > >>>>> 		if (pmic->irq >= 0) {
> > >>>>>
> > >>>>> i think the code before your patch was wrong as linux irqs start with 0.
> > >>>>>
> > >>>>> 	John
> > >>>> Hi John,
> > >>>>
> > >>>> Thanks, I will modify this.
> > >>>
> > >>> Linux irq start from 1, 0 is invalid. I can't find the document saying
> > >>> this now, but you could see this from irq_create_mapping() in
> > >>> kernel/irq/irqdomain.c
> > >>>
> > >>> I think the code should have check return from platform_get_irq and
> > >>> handle -EPROBE_DEFER, but maybe it should be another patch?
> > >>>
> > >>> BTW, in this function, it is possible that pmic->irq_domain will be NULL
> > >>> in fail_irq error handling. We should check before calling
> > >>> irq_domain_remove.
> > >>>
> > >>> Joe.C
> > >>>
> > >>
> > >> Hi,
> > >>
> > >> looking at
> > >> http://lxr.free-electrons.com/source/drivers/base/platform.c#L87 there
> > >> is a check in line #100 ret >= 0
> > >>
> > >> checking the return value of pmic->irq = platform_get_irq(pdev, 0);
> > >> should follow the same pattern i think .. unless i have a thinko and am
> > >> reading the code wrong.
> > > 
> > > 
> > > I'm not sure why platform_get_irq() check for 0, but I think the code
> > > logic is differnet.
> > > 
> > > When platform_get_irq() return 0 to our code, it means we don't have
> > > valid irq to use. In this case it doesn't make any sense to continue
> > > init irq.
> > > 
> > > 
> > > Joe.C
> > > 
> > 
> > 
> > --> http://lwn.net/Articles/470820/
> > 
> > indeed ARM has changed this is seems. was not aware of this change,
> > sorry for the noise
> > 
> > 	John
> 
> Hi Lee/Joe/John,
> 
> Thanks for comment, that means we can keep this patch for 4.6-rc1
> regression (RTC get NULL irq issue), right?

Just re-send everything with any Acks that you collected.

> I will send another patch to fixed above error handling problem.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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