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

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Message-ID: <1459431711.395.6.camel@mtksdaap41>
Date:	Thu, 31 Mar 2016 21:41:51 +0800
From:	Yingjoe Chen <yingjoe.chen@...iatek.com>
To:	John Crispin <blogic@...nwrt.org>
CC:	Henry Chen <henryc.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>,
	"Matthias Brugger" <matthias.bgg@...il.com>,
	Lee Jones <lee.jones@...aro.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux@...ck-us.net>
Subject: Re: [PATCH] mfd: mt6397: irq domain should initialize before
 mfd_add_devices()

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