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pwm: imx27: Fix variable truncation in .apply()

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Fix a variable truncation when calculating period in microseconds as
part of the solution for the ERR051198 in .apply() callback.

Example scenario:
 - Period of 3us (PWMPR = 196 and prescaler = 1)
 - Expected value in tmp: 198000000000 (NSEC_PER_SEC * (196 + 2) * 1)
 - Actual value is 431504384 (truncation to u32)

Signed-off-by: Ronaldo Nunez <rnunez@baylibre.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Link: https://patch.msgid.link/20260522191348.6227-1-rnunez@baylibre.com
Fixes: a25351e4c7 ("pwm: imx27: Workaround of the pwm output bug when decrease the duty cycle")
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>
This commit is contained in:
Ronaldo Nunez 2026-05-22 16:13:48 -03:00 committed by Uwe Kleine-König
parent c84291ce0e
commit dc9e08fdbc
1 changed files with 7 additions and 1 deletions
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8
drivers/pwm/pwm-imx27.c
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@ -200,7 +200,7 @@ static void pwm_imx27_wait_fifo_slot(struct pwm_chip *chip,
static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
const struct pwm_state *state)
{
unsigned long period_cycles, duty_cycles, prescale, period_us, tmp;
unsigned long period_cycles, duty_cycles, prescale, period_us;
struct pwm_imx27_chip *imx = to_pwm_imx27_chip(chip);
unsigned long long c;
unsigned long long clkrate;
@ -208,6 +208,7 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
int val;
int ret;
u32 cr;
u64 tmp;
clkrate = clk_get_rate(imx->clks[PWM_IMX27_PER].clk);
c = clkrate * state->period;
@ -249,6 +250,11 @@ static int pwm_imx27_apply(struct pwm_chip *chip, struct pwm_device *pwm,
val = readl(imx->mmio_base + MX3_PWMPR);
val = val >= MX3_PWMPR_MAX ? MX3_PWMPR_MAX : val;
cr = readl(imx->mmio_base + MX3_PWMCR);
/*
* tmp stores period in nanoseconds. Result fits in u64 since
* val <= 0xfffe and prescaler in [1, 0x1000].
*/
tmp = NSEC_PER_SEC * (u64)(val + 2) * MX3_PWMCR_PRESCALER_GET(cr);
tmp = DIV_ROUND_UP_ULL(tmp, clkrate);
period_us = DIV_ROUND_UP_ULL(tmp, 1000);