linux-kernel - Re: [PATCH] soc: mediatek: PMIC wrap: Enable STAUPD_PRD before WDT_SRC

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Date:	Mon, 4 Jan 2016 11:05:03 +0800
From:	Henry Chen <henryc.chen@...iatek.com>
To:	Daniel Kurtz <djkurtz@...omium.org>
CC:	Matthias Brugger <matthias.bgg@...il.com>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] soc: mediatek: PMIC wrap: Enable STAUPD_PRD before
 WDT_SRC_EN enabled.

On Thu, 2015-12-31 at 22:19 +0800, Daniel Kurtz wrote:
> On Wed, Dec 30, 2015 at 8:36 PM, Henry Chen <henryc.chen@...iatek.com> wrote:
> >
> > The STAUPD_TRIG will be enable when WDT_INT enable on probe function, if
> > doesn't enable STAUPD_PRD together, interrupt will be triggered because
> > STAUPD timeout. To avoid unexpected interrupt, enable periodic status
> > update which will be updated to PMIC every selected time period.
> 
> Sorry, I don't really understand this.
> 
> What exactly is triggering the unexpected watchdog interrupt (WDT_INT)?
> 
> How does setting STAUPD_PRD disable this "unexpected interrupt"?
> 
Yes, WDT_INT was triggered because the bit[25] of WDT_SRC_EN was
enabled:

bit[25] STAUPD_TRIG: STAUPD trigger signal timeout monitor

Setting STAUPD_PRD will update the status of PMIC periodic to avoid this
watchdog timeout.


> From the MT8173 Datasheet, I can see that the value written to
> STAUPD_PRD is the "periodic status update timing (period)".
> 
> > Signed-off-by: Henry Chen <henryc.chen@...iatek.com>
> > ---
> >  drivers/soc/mediatek/mtk-pmic-wrap.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/soc/mediatek/mtk-pmic-wrap.c b/drivers/soc/mediatek/mtk-pmic-wrap.c
> > index a8cde17..6e5c20f 100644
> > --- a/drivers/soc/mediatek/mtk-pmic-wrap.c
> > +++ b/drivers/soc/mediatek/mtk-pmic-wrap.c
> > @@ -904,6 +904,11 @@ static int pwrap_probe(struct platform_device *pdev)
> >                 return -ENODEV;
> >         }
> >
> > +       /*
> > +        * Enable periodic status update which will be updated to PMIC
> > +        * every selected time period.
> > +        */
> > +       pwrap_writel(wrp, 0x5, PWRAP_STAUPD_PRD);
> 
> nit: Perhaps use a define for 5, and specify the real period value.
> Something like this:
> 
> #define PWRAP_STAUPD_98_5US  5
> 
ok.

> 
> >         /* Initialize watchdog, may not be done by the bootloader */
> >         pwrap_writel(wrp, 0xf, PWRAP_WDT_UNIT);
> >         pwrap_writel(wrp, 0xffffffff, PWRAP_WDT_SRC_EN);
> > --
> > 1.9.1
> >
> > --
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