linux-kernel - Re: [PATCH v3 09/14] rtc: pcf2127: set PWRMNG value for PCF2131

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Message-Id: <20230123170731.6064430c50f5fb7b484d8734@hugovil.com>
Date:   Mon, 23 Jan 2023 17:07:31 -0500
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Bruno Thomsen <bruno.thomsen@...il.com>, a.zummo@...ertech.it,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        linux-rtc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Hugo Villeneuve <hvilleneuve@...onoff.com>
Subject: Re: [PATCH v3 09/14] rtc: pcf2127: set PWRMNG value for PCF2131

On Fri, 20 Jan 2023 17:39:17 +0100
Alexandre Belloni <alexandre.belloni@...tlin.com> wrote:

> Hello,
> 
> On 07/01/2023 19:36:06+0100, Bruno Thomsen wrote:
> > Den tor. 15. dec. 2022 kl. 16.19 skrev Hugo Villeneuve <hugo@...ovil.com>:
> > >
> > > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > >
> > > Default PWRMNG[2:0] bits are set to 000b for PCF2127/29, but to
> > > 111b for PCF2131.
> > >
> > > Set these bits to 000b to select same mode as PCF2127/29.
> > >
> > > Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > 
> > Reviewed-by: Bruno Thomsen <bruno.thomsen@...il.com>
> > 
> > I think it's a good idea[1] but there have been concerns about
> > setting default values in the past[2]. In case somebody needs
> > a different behaviour they should add a device tree property.
> > 
> > [1] https://lore.kernel.org/linux-rtc/20190910143945.9364-1-bruno.thomsen@gmail.com/
> > [2] https://lore.kernel.org/linux-rtc/20191211163354.GC1463890@piout.net/
> 
> I confirm this is still my point of view and I won't take this patch as
> this may break existing users.

Patch dropped.

 
> > 
> > > ---
> > >  drivers/rtc/rtc-pcf2127.c | 15 +++++++++++++++
> > >  1 file changed, 15 insertions(+)
> > >
> > > diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
> > > index 68af4d0438b8..241189ee4a05 100644
> > > --- a/drivers/rtc/rtc-pcf2127.c
> > > +++ b/drivers/rtc/rtc-pcf2127.c
> > > @@ -53,6 +53,7 @@
> > >  #define PCF2127_BIT_CTRL3_BLF                  BIT(2)
> > >  #define PCF2127_BIT_CTRL3_BF                   BIT(3)
> > >  #define PCF2127_BIT_CTRL3_BTSE                 BIT(4)
> > > +#define PCF2127_CTRL3_PWRMNG_MASK              GENMASK(7, 5)
> > >  /* Control register 4 */
> > >  #define PCF2131_REG_CTRL4              0x03
> > >  #define PCF2131_BIT_CTRL4_TSF4                 BIT(4)
> > > @@ -1129,6 +1130,20 @@ static int pcf2127_probe(struct device *dev, struct regmap *regmap,
> > >         regmap_clear_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
> > >                                 PCF2127_BIT_CTRL1_POR_OVRD);
> > >
> > > +       /* Make sure PWRMNG[2:0] is set to 000b. This is the default for
> > > +        * PCF2127/29, but not for PCF2131 (default of 111b).
> > > +        *
> > > +        * PWRMNG[2:0]  = 000b:
> > > +        *   battery switch-over function is enabled in standard mode;
> > > +        *   battery low detection function is enabled
> > > +        */
> > > +       ret = regmap_clear_bits(pcf2127->regmap, PCF2127_REG_CTRL3,
> > > +                               PCF2127_CTRL3_PWRMNG_MASK);
> > > +       if (ret < 0) {
> > > +               dev_err(dev, "PWRMNG config failed\n");
> > > +               return ret;
> > > +       }
> > > +
> > >         ret = regmap_read(pcf2127->regmap, pcf2127->cfg->reg_clkout, &val);
> > >         if (ret < 0)
> > >                 return ret;
> > > --
> > > 2.30.2
> > >
> 
> -- 
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com
> 


-- 
Hugo Villeneuve <hugo@...ovil.com>