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rtc: zynqmp: rework set_offset

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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 <harini.t@amd.com>
Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>
Reviewed-by: Harini T <harini.t@amd.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Link: https://patch.msgid.link/20260122-zynqmp-rtc-updates-v4-4-d4edb966b499@vaisala.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
This commit is contained in:
Tomas Melin 2026-01-22 13:53:48 +00:00 committed by Alexandre Belloni
parent 0f9989443f
commit 9f5af70268
1 changed files with 13 additions and 20 deletions
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33
drivers/rtc/rtc-zynqmp.c
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@ -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, 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;
calibval = max_tick + freq;
if (fract_tick)
calibval |= RTC_FR_EN;
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));