RE: [PATCH V2] rtc: zynqmp: Update seconds time programming logic

[Anurag Kumar Vulisha]

Hi Alexandre,

> -----Original Message-----
> From: Alexandre Belloni [mailto:alexandre.belloni@xxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, April 20, 2016 7:33 PM
> To: Anurag Kumar Vulisha <anuragku@xxxxxxxxxx>
> Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>; Soren Brinkmann
> <sorenb@xxxxxxxxxx>; Michal Simek <michals@xxxxxxxxxx>; rtc-
> linux@xxxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; Punnaiah Choudary Kalluri <punnaia@xxxxxxxxxx>;
> Anirudha Sarangi <anirudh@xxxxxxxxxx>; Srikanth Vemula
> <svemula@xxxxxxxxxx>; Srinivas Goud <sgoud@xxxxxxxxxx>; Anurag Kumar
> Vulisha <anuragku@xxxxxxxxxx>
> Subject: Re: [PATCH V2] rtc: zynqmp: Update seconds time programming
> logic
>
> On 20/04/2016 at 19:21:19 +0530, Anurag Kumar Vulisha wrote :
> > We programe RTC time using SET_TIME_WRITE register and read the RTC
> > current time using CURRENT_TIME register. When we set the time by
> > writing into SET_TIME_WRITE Register and immediately try to read the
> > rtc time from CURRENT_TIME register, the previous old value is
> > returned instead of the new loaded time. This is because RTC takes
> > nearly 1 sec to update the  new loaded value into the CURRENT_TIME
> > register. This behaviour is expected in our RTC IP.
> >
> > This patch updates the driver to read the current time from
> > SET_TIME_WRITE register instead of CURRENT_TIME when rtc time is
> > requested within an 1sec period after setting the RTC time. Doing so
> > will ensure the correct time is given to the user.
> >
> > Since there is an delay of 1sec in updating the CURRENT_TIME we are
> > loading set time +1sec while programming the SET_TIME_WRITE register,
> > doing this will give correct time without any delay when read from
> CURRENT_TIME.
> >
> > This patch updates the above said.
> >
> > Signed-off-by: Anurag Kumar Vulisha <anuragku@xxxxxxxxxx>
> > ---
> >  Changes in v2:
> >     1. Updated the Time programming logic as suggested by Alexandre
> Belloni
> >     2. Changed the commit message
> > ---
> >  drivers/rtc/rtc-zynqmp.c | 41
> > ++++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 36 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c index
> > f87f971..ba4203a 100644
> > --- a/drivers/rtc/rtc-zynqmp.c
> > +++ b/drivers/rtc/rtc-zynqmp.c
> > @@ -64,6 +64,12 @@ static int xlnx_rtc_set_time(struct device *dev, struct
> rtc_time *tm)
> >     struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
> >     unsigned long new_time;
> >
> > +   /*
> > +    * The value written will be updated after 1 sec into the
> > +    * seconds read register, so we need to program time +1 sec
> > +    * to get the correct time on read.
> > +    */
> > +   tm->tm_sec += 1;
> >     new_time = rtc_tm_to_time64(tm);
> >
> >     if (new_time > RTC_SEC_MAX_VAL)
> > @@ -78,14 +84,41 @@ static int xlnx_rtc_set_time(struct device *dev,
> > struct rtc_time *tm)
> >
> >     writel(new_time, xrtcdev->reg_base + RTC_SET_TM_WR);
> >
> > +   /*
> > +    * Clear the rtc interrupt status register after setting the
> > +    * time. During a read_time function, the code should read the
> > +    * RTC_INT_STATUS register and if bit 0 is still 0, it means
> > +    * that one second has not elapsed yet since RTC was set and
> > +    * the current time should be read from SET_TIME_READ register;
> > +    * otherwise, CURRENT_TIME register is read to report the time
> > +    */
> > +   writel(RTC_INT_SEC, xrtcdev->reg_base + RTC_INT_STS);
> > +
> >     return 0;
> >  }
> >
> >  static int xlnx_rtc_read_time(struct device *dev, struct rtc_time
> > *tm)  {
> > +   int status;
> >     struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev);
> >
> > -   rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_CUR_TM), tm);
> > +   status = readl(xrtcdev->reg_base + RTC_INT_STS);
> > +
> > +   if (status & RTC_INT_SEC) {
> > +           /*
> > +            * RTC has updated the CURRENT_TIME with the time written
> into
> > +            * SET_TIME_WRITE register.
> > +            */
> > +           rtc_time64_to_tm(readl(xrtcdev->reg_base +
> RTC_CUR_TM), tm);
> > +   } else {
> > +           /*
> > +            * Time written in SET_TIME_WRITE has not yet updated into
> > +            * the seconds read register, so read the time from the
> > +            * SET_TIME_WRITE instead of CURRENT_TIME register.
> > +            */
> > +           rtc_time64_to_tm(readl(xrtcdev->reg_base +
> RTC_SET_TM_RD), tm);
> > +           tm->tm_sec -= 1;
>
> Well, I didn't point it out directly earlier but this doesn't work while my
> example is working:
> rtc_time64_to_tm(readl(xrtcdev->reg_base + RTC_SET_TM_RD) - 1, tm);
> Think about what is happening when tm->tm_sec == 0 ...
>

Thanks  for pointing it out, will change this part

Regards,
Anurag Kumar V

> > +   }
> >
> >     return rtc_valid_tm(tm);
> >  }
> > @@ -166,11 +199,9 @@ static irqreturn_t xlnx_rtc_interrupt(int irq, void
> *id)
> >     if (!(status & (RTC_INT_SEC | RTC_INT_ALRM)))
> >             return IRQ_NONE;
> >
> > -   /* Clear interrupt */
> > -   writel(status, xrtcdev->reg_base + RTC_INT_STS);
> > +   /* Clear RTC_INT_ALRM interrupt only */
> > +   writel(RTC_INT_ALRM, xrtcdev->reg_base + RTC_INT_STS);
> >
> > -   if (status & RTC_INT_SEC)
> > -           rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_UF);
> >     if (status & RTC_INT_ALRM)
> >             rtc_update_irq(xrtcdev->rtc, 1, RTC_IRQF | RTC_AF);
> >
> > --
> > 2.1.2
> >
>
> --
> Alexandre Belloni, Free Electrons
> Embedded Linux, Kernel and Android engineering
> http://free-electrons.com


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