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 <[email protected]> > --- > 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 ... > + } > > 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
