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 <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Fixes: 2b62c89 ("pwm: Add Loongson PWM controller support")
Signed-off-by: Uwe Kleine-König <[email protected]>
Reviewed-by: Binbin Zhou <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Uwe Kleine-König <[email protected]>

Author: ukleinek

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 */