linux-kernel - [PATCH] leds: qcom-lpg: Fix PWM period limits

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Message-ID: <20230512165524.3367443-1-quic_bjorande@quicinc.com>
Date:   Fri, 12 May 2023 09:55:24 -0700
From:   Bjorn Andersson <quic_bjorande@...cinc.com>
To:     Pavel Machek <pavel@....cz>, Lee Jones <lee@...nel.org>,
        "Anjelique Melendez" <quic_amelende@...cinc.com>
CC:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, "Luca Weiss" <luca@...tu.xyz>,
        <linux-leds@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-msm@...r.kernel.org>
Subject: [PATCH] leds: qcom-lpg: Fix PWM period limits

The introduction of high resolution PWM support moved the parenthesis of
the divisions in the calculation of min and max period. The result in
both divisions is in most cases 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")
Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
---

This fixes the regression in v6.4-rc1.

 drivers/leds/rgb/leds-qcom-lpg.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/leds/rgb/leds-qcom-lpg.c b/drivers/leds/rgb/leds-qcom-lpg.c
index c9cea797a697..7287fadc00df 100644
--- 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;
 
-- 
2.25.1