leds: qcom-lpg: Fix PWM period limits

The introduction of high resolution PWM support changed the order of the
operations in the calculation of min and max period. The result in both
divisions is in most cases a truncation to 0, which limits the period to
the range of [0, 0].

Both numerators (and denominators) are within 64 bits, so the whole
expression can be put directly into the div64_u64, instead of doing it
partially.

Fixes: b00d2ed37617 ("leds: rgb: leds-qcom-lpg: Add support for high resolution PWM")
Reviewed-by: Caleb Connolly <caleb.connolly@linaro.org>
Tested-by: Steev Klimaszewski <steev@kali.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Acked-by: Lee Jones <lee@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-QRD
Link: https://lore.kernel.org/r/20230515162604.649203-1-quic_bjorande@quicinc.com
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
index 55a0372..1c84981 100644 (file)
--- a/drivers/leds/rgb/leds-qcom-lpg.c
+++ b/drivers/leds/rgb/leds-qcom-lpg.c
@@ -312,14 +312,14 @@ static int lpg_calc_freq(struct lpg_channel *chan, uint64_t period)
                max_res = LPG_RESOLUTION_9BIT;
        }
 
-       min_period = (u64)NSEC_PER_SEC *
-                       div64_u64((1 << pwm_resolution_arr[0]), clk_rate_arr[clk_len - 1]);
+       min_period = div64_u64((u64)NSEC_PER_SEC * (1 << pwm_resolution_arr[0]),
+                              clk_rate_arr[clk_len - 1]);
        if (period <= min_period)
                return -EINVAL;
 
        /* Limit period to largest possible value, to avoid overflows */
-       max_period = (u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV *
-                       div64_u64((1 << LPG_MAX_M), 1024);
+       max_period = div64_u64((u64)NSEC_PER_SEC * max_res * LPG_MAX_PREDIV * (1 << LPG_MAX_M),
+                              1024);
        if (period > max_period)
                period = max_period;