linux-kernel - [PATCH] pwm: mediatek: Add error handling for zero rate in PWM state

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Message-ID: <20251215104037.3100485-1-payne.lin@mediatek.com>
Date: Mon, 15 Dec 2025 18:40:32 +0800
From: 20190311120055 created <payne.lin@...iatek.com>
To: Uwe Kleine-König <ukleinek@...nel.org>, "Matthias
 Brugger" <matthias.bgg@...il.com>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>
CC: <linux-pwm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-mediatek@...ts.infradead.org>,
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	<sirius.wang@...iatek.com>, <vince-wl.liu@...iatek.com>,
	<jh.hsu@...iatek.com>, Payne Lin <payne.lin@...iatek.com>
Subject: [PATCH] pwm: mediatek: Add error handling for zero rate in PWM state

From: Payne Lin <payne.lin@...iatek.com>

Added a check to handle cases where the rate is zero in the
mtk_disp_pwm_get_state function. This prevents division by zero errors
when calculating the period.
- Added error message for zero rate scenario

Signed-off-by: Payne Lin <payne.lin@...iatek.com>
---
 drivers/pwm/pwm-mtk-disp.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
index bafd6b6195f6..dd0ae041af70 100644
--- a/drivers/pwm/pwm-mtk-disp.c
+++ b/drivers/pwm/pwm-mtk-disp.c
@@ -176,19 +176,18 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip,
 	struct mtk_disp_pwm *mdp = to_mtk_disp_pwm(chip);
 	u64 rate, period, high_width;
 	u32 clk_div, pwm_en, con0, con1;
-	int err;
+	int ret;
 
-	err = clk_prepare_enable(mdp->clk_main);
-	if (err < 0) {
-		dev_err(pwmchip_parent(chip), "Can't enable mdp->clk_main: %pe\n", ERR_PTR(err));
-		return err;
+	ret = clk_prepare_enable(mdp->clk_main);
+	if (ret < 0) {
+		dev_err(pwmchip_parent(chip), "Can't enable mdp->clk_main: %pe\n", ERR_PTR(ret));
+		goto err_handle;
 	}
 
-	err = clk_prepare_enable(mdp->clk_mm);
-	if (err < 0) {
-		dev_err(pwmchip_parent(chip), "Can't enable mdp->clk_mm: %pe\n", ERR_PTR(err));
-		clk_disable_unprepare(mdp->clk_main);
-		return err;
+	ret = clk_prepare_enable(mdp->clk_mm);
+	if (ret < 0) {
+		dev_err(pwmchip_parent(chip), "Can't enable mdp->clk_mm: %pe\n", ERR_PTR(ret));
+		goto err_disable_clk_main;
 	}
 
 	/*
@@ -212,15 +211,23 @@ static int mtk_disp_pwm_get_state(struct pwm_chip *chip,
 	 * period has 12 bits, clk_div 11 and NSEC_PER_SEC has 30,
 	 * so period * (clk_div + 1) * NSEC_PER_SEC doesn't overflow.
 	 */
+	if (rate == 0) {
+		dev_err(pwmchip_parent(chip), "rate is zero, cannot calculate period\n");
+		ret = -EINVAL;
+		goto err_disable_clk_mm;
+	}
 	state->period = DIV64_U64_ROUND_UP(period * (clk_div + 1) * NSEC_PER_SEC, rate);
 	high_width = FIELD_GET(PWM_HIGH_WIDTH_MASK, con1);
 	state->duty_cycle = DIV64_U64_ROUND_UP(high_width * (clk_div + 1) * NSEC_PER_SEC,
 					       rate);
 	state->polarity = PWM_POLARITY_NORMAL;
+
+err_disable_clk_mm:
 	clk_disable_unprepare(mdp->clk_mm);
+err_disable_clk_main:
 	clk_disable_unprepare(mdp->clk_main);
-
-	return 0;
+err_handle:
+	return ret;
 }
 
 static const struct pwm_ops mtk_disp_pwm_ops = {
-- 
2.45.2