[PATCH v3 5/6] rtc: zynqmp: rework set_offset
From: Tomas Melin <hidden>
Date: 2026-01-19 09:51:53
Also in:
linux-rtc, lkml
Subsystem:
real time clock (rtc) subsystem, the rest · Maintainers:
Alexandre Belloni, Linus Torvalds
set_offset was using remainder of do_div as tick_mult which resulted in wrong offset. Calibration value also assumed builtin calibration default. Update fract_offset to correctly calculate the value for negative offset and replace the for loop with division. Tested-by: Harini T <redacted> Signed-off-by: Tomas Melin <redacted> --- drivers/rtc/rtc-zynqmp.c | 33 +++++++++++++-------------------- 1 file changed, 13 insertions(+), 20 deletions(-)
diff --git a/drivers/rtc/rtc-zynqmp.c b/drivers/rtc/rtc-zynqmp.c
index 6740c3aed1897d4b50a02c4823a746d9c2ae2655..1bc957b3a9058aa1d809696c13662ecef0437a92 100644
--- a/drivers/rtc/rtc-zynqmp.c
+++ b/drivers/rtc/rtc-zynqmp.c@@ -208,13 +208,13 @@ static int xlnx_rtc_read_offset(struct device *dev, long *offset) static int xlnx_rtc_set_offset(struct device *dev, long offset) { struct xlnx_rtc_dev *xrtcdev = dev_get_drvdata(dev); - unsigned long long rtc_ppb = RTC_PPB; - unsigned int tick_mult = do_div(rtc_ppb, xrtcdev->freq); - unsigned char fract_tick = 0; + int max_tick, tick_mult, fract_offset, fract_part; + int freq = xrtcdev->freq; unsigned int calibval; - short int max_tick; - int fract_offset; + int fract_data = 0; + /* Tick to offset multiplier */ + tick_mult = DIV_ROUND_CLOSEST(RTC_PPB, xrtcdev->freq); if (offset < RTC_MIN_OFFSET || offset > RTC_MAX_OFFSET) return -ERANGE;
@@ -223,29 +223,22 @@ static int xlnx_rtc_set_offset(struct device *dev, long offset) /* Number fractional ticks for given offset */ if (fract_offset) { - if (fract_offset < 0) { - fract_offset = fract_offset + tick_mult; + fract_part = DIV_ROUND_UP(tick_mult, RTC_FR_MAX_TICKS); + fract_data = fract_offset / fract_part; + /* Subtract one from max_tick while adding fract_offset */ + if (fract_offset < 0 && fract_data) { max_tick--; - } - if (fract_offset > (tick_mult / RTC_FR_MAX_TICKS)) { - for (fract_tick = 1; fract_tick < 16; fract_tick++) { - if (fract_offset <= - (fract_tick * - (tick_mult / RTC_FR_MAX_TICKS))) - break; - } + fract_data += RTC_FR_MAX_TICKS; } } /* Zynqmp RTC uses second and fractional tick * counters for compensation */ - calibval = max_tick + RTC_CALIB_DEF; - - if (fract_tick) - calibval |= RTC_FR_EN; + calibval = max_tick + freq; - calibval |= (fract_tick << RTC_FR_DATSHIFT); + if (fract_data) + calibval |= (RTC_FR_EN | (fract_data << RTC_FR_DATSHIFT)); writel(calibval, (xrtcdev->reg_base + RTC_CALIB_WR));
--
2.47.3