linux-kernel - [PATCH v3] pwm: mtk_disp: Fix the disable flow of disp

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Message-ID: <20230531031001.7440-1-shuijing.li@mediatek.com>
Date:   Wed, 31 May 2023 11:10:01 +0800
From:   Shuijing Li <shuijing.li@...iatek.com>
To:     <thierry.reding@...il.com>, <u.kleine-koenig@...gutronix.de>,
        <matthias.bgg@...il.com>, <angelogioacchino.delregno@...labora.com>
CC:     <devicetree@...r.kernel.org>, <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>,
        <jitao.shi@...iatek.com>, Shuijing Li <shuijing.li@...iatek.com>,
        Fei Shao <fshao@...omium.org>
Subject: [PATCH v3] pwm: mtk_disp: Fix the disable flow of disp_pwm

There is a flow error in the original mtk_disp_pwm_apply() function.
If this function is called when the clock is disabled, there will be a
chance to operate the disp_pwm register, resulting in disp_pwm exception.
Fix this accordingly.

Fixes: 888a623db5d0 ("pwm: mtk-disp: Implement atomic API .apply()")
Signed-off-by: Shuijing Li <shuijing.li@...iatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@...il.com>
Tested-by: Fei Shao <fshao@...omium.org>
---
Changes in v3:
Add Fixes per suggestion from the previous thread:
https://lore.kernel.org/lkml/CAC=S1nhVrbaAh2u7rG-=-RubsxTZvMBRZO-t0NA8jG7M8187EA@mail.gmail.com/
Changes in v2:
Use
if (A && B) {
        something();
}
instead of
if (A) {
        if (B) {
                something();
        }
}
per suggestion from the previous thread:
https://lore.kernel.org/lkml/20230515140346.bxeu6xewi6a446nd@pengutronix.de/
---
 drivers/pwm/pwm-mtk-disp.c | 13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/drivers/pwm/pwm-mtk-disp.c b/drivers/pwm/pwm-mtk-disp.c
index 79e321e96f56..2401b6733241 100644
--- a/drivers/pwm/pwm-mtk-disp.c
+++ b/drivers/pwm/pwm-mtk-disp.c
@@ -79,14 +79,11 @@ static int mtk_disp_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (state->polarity != PWM_POLARITY_NORMAL)
 		return -EINVAL;
 
-	if (!state->enabled) {
-		mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN, mdp->data->enable_mask,
-					 0x0);
-
-		if (mdp->enabled) {
-			clk_disable_unprepare(mdp->clk_mm);
-			clk_disable_unprepare(mdp->clk_main);
-		}
+	if (!state->enabled && mdp->enabled) {
+		mtk_disp_pwm_update_bits(mdp, DISP_PWM_EN,
+					 mdp->data->enable_mask, 0x0);
+		clk_disable_unprepare(mdp->clk_mm);
+		clk_disable_unprepare(mdp->clk_main);
 
 		mdp->enabled = false;
 		return 0;
-- 
2.40.1