linux-kernel - Re: [PATCH v3 11/14] rtc: pcf2127: adapt time/date registers write sequence for PCF2131

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Message-Id: <20230123155520.22a20149745dcbd536536e8f@hugovil.com>
Date:   Mon, 23 Jan 2023 15:55:20 -0500
From:   Hugo Villeneuve <hugo@...ovil.com>
To:     Bruno Thomsen <bruno.thomsen@...il.com>
Cc:     a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        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 11/14] rtc: pcf2127: adapt time/date registers write
 sequence for PCF2131

On Sat, 7 Jan 2023 19:44:23 +0100
Bruno Thomsen <bruno.thomsen@...il.com> wrote:

> Den tor. 15. dec. 2022 kl. 16.19 skrev Hugo Villeneuve <hugo@...ovil.com>:
> >
> > From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> >
> > The sequence for updating the time/date registers is slightly
> > different between PCF2127/29 and PCF2131.
> >
> > For PCF2127/29, during write operations, the time counting
> > circuits (memory locations 03h through 09h) are automatically blocked.
> >
> > For PCF2131, time/date registers write access requires setting the
> > STOP bit and sending the clear prescaler instruction (CPR). STOP then
> > needs to be released once write operation is completed.
> >
> > Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> > ---
> >  drivers/rtc/rtc-pcf2127.c | 38 +++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 37 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/rtc/rtc-pcf2127.c b/drivers/rtc/rtc-pcf2127.c
> > index e4b78b9c03f9..11fbdab6bf01 100644
> > --- a/drivers/rtc/rtc-pcf2127.c
> > +++ b/drivers/rtc/rtc-pcf2127.c
> > @@ -39,6 +39,7 @@
> >  #define PCF2127_REG_CTRL1              0x00
> >  #define PCF2127_BIT_CTRL1_POR_OVRD             BIT(3)
> >  #define PCF2127_BIT_CTRL1_TSF1                 BIT(4)
> > +#define PCF2127_BIT_CTRL1_STOP                 BIT(5)
> >  /* Control register 2 */
> >  #define PCF2127_REG_CTRL2              0x01
> >  #define PCF2127_BIT_CTRL2_AIE                  BIT(1)
> > @@ -70,6 +71,7 @@
> >  #define PCF2131_REG_SR_RESET           0x05
> >  #define PCF2131_SR_RESET_READ_PATTERN  0b00100100 /* Fixed pattern. */
> >  #define PCF2131_SR_RESET_RESET_CMD     0x2C /* SR is bit 3. */
> > +#define PCF2131_SR_RESET_CPR_CMD       0xA4 /* CPR is bit 7. */
> 
> Replace 0xA4 with (BIT(2) | BIT(5) | BIT(7)) or
> (PCF2131_SR_RESET_READ_PATTERN | BIT(7))

Done.

 
> >  /* Time and date registers */
> >  #define PCF2127_REG_TIME_DATE_BASE     0x03
> >  #define PCF2131_REG_TIME_DATE_BASE     0x07 /* Register 0x06 is 100th seconds,
> > @@ -307,7 +309,31 @@ static int pcf2127_rtc_set_time(struct device *dev, struct rtc_time *tm)
> >         /* year */
> >         buf[i++] = bin2bcd(tm->tm_year - 100);
> >
> > -       /* write register's data */
> > +       /* Write access to time registers:
> > +        * PCF2127/29: no special action required.
> > +        * PCF2131:    requires setting the STOP bit. STOP bit needs to
> > +        *             be cleared after time registers are updated.
> > +        *             It is also recommended to set CPR bit, although
> > +        *             write access will work without it.
> > +        */
> > +       if (pcf2127->cfg->has_reset_reg) {
> > +               err = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
> > +                                        PCF2127_BIT_CTRL1_STOP,
> > +                                        PCF2127_BIT_CTRL1_STOP);
> > +               if (err) {
> > +                       dev_err(dev, "setting STOP bit failed\n");
> > +                       return err;
> > +               }
> > +
> > +               err = regmap_write(pcf2127->regmap, pcf2127->cfg->reg_reset,
> > +                                  PCF2131_SR_RESET_CPR_CMD);
> > +               if (err) {
> > +                       dev_err(dev, "sending CPR cmd failed\n");
> > +                       return err;
> > +               }
> > +       }
> > +
> > +       /* write time register's data */
> >         err = regmap_bulk_write(pcf2127->regmap, pcf2127->cfg->regs_td_base, buf, i);
> >         if (err) {
> >                 dev_err(dev,
> > @@ -315,6 +341,16 @@ static int pcf2127_rtc_set_time(struct device *dev, struct rtc_time *tm)
> >                 return err;
> >         }
> >
> > +       if (pcf2127->cfg->has_reset_reg) {
> > +               /* Clear STOP bit (PCF2131 only) after write is completed. */
> > +               err = regmap_update_bits(pcf2127->regmap, PCF2127_REG_CTRL1,
> > +                                        PCF2127_BIT_CTRL1_STOP, 0);
> > +               if (err) {
> > +                       dev_err(dev, "clearing STOP bit failed\n");
> > +                       return err;
> > +               }
> > +       }
> > +
> >         return 0;
> >  }
> >
> > --
> > 2.30.2
> >
> 


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