pwm: tiehrpwm: Fix corner case in clock divisor calculation

[ Upstream commit 00f83f0e07e44e2f1fb94b223e77ab7b18ee2d7d ]

The function set_prescale_div() is responsible for calculating the clock
divisor settings such that the input clock rate is divided down such that
the required period length is at most 0x10000 clock ticks. If period_cycles
is an integer multiple of 0x10000, the divisor period_cycles / 0x10000 is
good enough. So round up in the calculation of the required divisor and
compare it using >= instead of >.

Fixes: 19891b2 ("pwm: pwm-tiehrpwm: PWM driver support for EHRPWM")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Link: https://lore.kernel.org/r/85488616d7bfcd9c32717651d0be7e330e761b9c.1754927682.git.u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Ulrich Hecht <uli@kernel.org>

Author: ukleinek

drivers/pwm/pwm-tiehrpwm.c

@@ -180,7 +180,7 @@ static int set_prescale_div(unsigned long rqst_prescaler, u16 *prescale_div,
 
 			*prescale_div = (1 << clkdiv) *
 					(hspclkdiv ? (hspclkdiv * 2) : 1);
-			if (*prescale_div > rqst_prescaler) {
+			if (*prescale_div >= rqst_prescaler) {
 				*tb_clk_div = (clkdiv << TBCTL_CLKDIV_SHIFT) |
 					(hspclkdiv << TBCTL_HSPCLKDIV_SHIFT);
 				return 0;
@@ -279,7 +279,7 @@ static int ehrpwm_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
 	pc->period_cycles[pwm->hwpwm] = period_cycles;
 
 	/* Configure clock prescaler to support Low frequency PWM wave */
-	if (set_prescale_div(period_cycles/PERIOD_MAX, &ps_divval,
+	if (set_prescale_div(DIV_ROUND_UP(period_cycles, PERIOD_MAX), &ps_divval,
 			     &tb_divval)) {
 		dev_err(chip->dev, "Unsupported values\n");
 		return -EINVAL;