linux-kernel - Re: [PATCH v8 4/5] rtc: mt6397: Add support for the MediaTek MT6358 RTC

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Date:   Wed, 4 Mar 2020 20:59:55 +0800
From:   Nicolas Boichat <drinkcat@...omium.org>
To:     Ran Bi <ran.bi@...iatek.com>
Cc:     Yingjoe Chen <yingjoe.chen@...iatek.com>,
        Hsin-Hsiung Wang <hsin-hsiung.wang@...iatek.com>,
        Lee Jones <lee.jones@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Josef Friedl <josef.friedl@...ed.at>,
        srv_heupstream <srv_heupstream@...iatek.com>,
        Frank Wunderlich <frank-w@...lic-files.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sean Wang <sean.wang@...iatek.com>,
        lkml <linux-kernel@...r.kernel.org>,
        Richard Fontana <rfontana@...hat.com>,
        Devicetree List <devicetree@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Eddie Huang <eddie.huang@...iatek.com>,
        linux-rtc@...r.kernel.org
Subject: Re: [PATCH v8 4/5] rtc: mt6397: Add support for the MediaTek MT6358 RTC

Hi,

On Mon, Feb 17, 2020 at 11:52 AM Ran Bi <ran.bi@...iatek.com> wrote:
>
> On Tue, 2020-02-04 at 00:50 +0800, Yingjoe Chen wrote:
> > > diff --git a/include/linux/mfd/mt6397/rtc.h b/include/linux/mfd/mt6397/rtc.h
> > > index f84b916..fffe34a 100644
> > > --- a/include/linux/mfd/mt6397/rtc.h
> > > +++ b/include/linux/mfd/mt6397/rtc.h
> > > @@ -18,7 +18,8 @@
> > >  #define RTC_BBPU_CBUSY         BIT(6)
> > >  #define RTC_BBPU_KEY            (0x43 << 8)
> > >
> > > -#define RTC_WRTGR              0x003c
> > > +#define RTC_WRTGR_MT6358       0x3a
> > > +#define RTC_WRTGR_MT6397       0x3c
> > >
> > >  #define RTC_IRQ_STA            0x0002
> > >  #define RTC_IRQ_STA_AL         BIT(0)
> > > @@ -57,6 +58,10 @@
> > >  #define MTK_RTC_POLL_DELAY_US  10
> > >  #define MTK_RTC_POLL_TIMEOUT   (jiffies_to_usecs(HZ))
> > >
> > > +struct mtk_rtc_data {
> > > +   u32                     wrtgr;
> > > +};
> > > +
> > >  struct mt6397_rtc {
> > >     struct device           *dev;
> > >     struct rtc_device       *rtc_dev;
> > > @@ -66,6 +71,15 @@ struct mt6397_rtc {
> > >     struct regmap           *regmap;
> > >     int                     irq;
> > >     u32                     addr_base;
> > > +   const struct mtk_rtc_data *data;
> > > +};
> > > +
> > > +static const struct mtk_rtc_data mt6358_rtc_data = {
> > > +   .wrtgr = RTC_WRTGR_MT6358,
> > > +};
> > > +
> > > +static const struct mtk_rtc_data mt6397_rtc_data = {
> > > +   .wrtgr = RTC_WRTGR_MT6397,
> > >  };
> >
> > Hi,
> >
> > Putting these in header file doesn't looks right to me.
> > Who need this? can you move them back to rtc-mt6397.c?
> > Joe.C
> >
>
> This could also effect kernel/drivers/power/reset/mt6323-poweroff.c
> which using same region of RTC registers.
> There are 2 ways of modification:
> 1. kernel/drivers/rtc/rtc-mt6397.c implement do_pwroff function and
> export to mt6323-poweroff.c
> 2. Just modify mt6323-poweroff.c file to compatible this patch. I mean
> using RTC_WRTGR_MT6397 to replace RTC_WRTGR. Or modify mt6323-poweroff.c
> like rtc-mt6397.c

Oh, I see, so basically both rtc-mt6397.c and mt6323-poweroff.c need
to know at what offset RTC_WRTGR actually is. Correct?

Is there any plan to have mt6323-poweroff.c support any of the other
PMICs (not just MT6323?)?

a. If not, I'd just add:
#define RTC_WRTGR_MT6323 RTC_WRTGR_MT6397
in rtc.h, for added clarity, use that in mt6323-poweroff.c
(s/RTC_WRTGR/RTC_WRTGR_MT6323/), and be done with it.

Actually, even if there's a plan, you can go ahead with this simpler
solution for now, and fix later when the issue comes up.

b. If you ever want to support multiple PMICs with mt6323-poweroff.c,
you'd need that offset for 2 different sub-devices under the same mfd,
so the matching logic belongs in the main mfd device, not in
rtc/poweroff driver.

So I'd move the matching logic in drivers/mfd/mt6397-core.c, and add
rtc_wrtgr offset (or a full _data structure) to `struct mt6397_chip`,
or, probably better, add a IORESOURCE_REG to the matching resources to
specify the offset (that's what drivers/mfd/88pm860x-core.c seems to
be doing, for example).

And then mt6323-poweroff.c should probably be renamed to mt6397-poweroff.c.

(actually, looking at this, I'm even questioning if mt6323-poweroff.c
should even exist, and if you should just fold it into rtc-mt6397.c?
Since they use the same registers?)

Hope this makes sense?

Best,