pwm: loongson: Fix u32 overflow in waveform calculation

mul_u64_u64_div_u64() returns an u64 that might be bigger than U32_MAX.
To properly handle this case it must not be directly assigned to an u32
value.

Use a wider type for duty and period to make the idiom:

	duty = mul_u64_u64_div_u64(...)
	if (duty > U32_MAX)
		duty = U32_MAX;

actually work as intended.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/r/44f3c764-8b65-49a9-b3ad-797e9fbb96f5@stanley.mountain
Fixes: 2b62c89448dd ("pwm: Add Loongson PWM controller support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@baylibre.com>
Reviewed-by: Binbin Zhou <zhoubinbin@loongson.cn>
Link: https://lore.kernel.org/r/20250412122124.1636152-2-u.kleine-koenig@baylibre.com
Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>

diff --git a/drivers/pwm/pwm-loongson.c b/drivers/pwm/pwm-loongson.c
index 412c67739ef9fc4a7857014f90a0bba2cf9e9588..6392c4e341363b3a606a76366e4322227ccbfbe8 100644 (file)
--- a/drivers/pwm/pwm-loongson.c
+++ b/drivers/pwm/pwm-loongson.c
@@ -118,7 +118,7 @@ static int pwm_loongson_enable(struct pwm_chip *chip, struct pwm_device *pwm)
 static int pwm_loongson_config(struct pwm_chip *chip, struct pwm_device *pwm,
                               u64 duty_ns, u64 period_ns)
 {
-       u32 duty, period;
+       u64 duty, period;
        struct pwm_loongson_ddata *ddata = to_pwm_loongson_ddata(chip);
 
        /* duty = duty_ns * ddata->clk_rate / NSEC_PER_SEC */