[PATCH v2 2/3] pwm: rockchip: Eliminate potential race condition when probing

[Simon South <simon@simonsouth.net>]

Commit 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running
PWMs") introduced a potential race condition in rockchip_pwm_probe() as the
function could disable the clock of a PWM device after having registered it
through a call to pwmchip_add().

Eliminate this possibility by moving the code that disables the clock of a
non-enabled PWM ahead of the code that registers the device.

Also refactor the code slightly to eliminate goto targets as the error
handlers no longer share any recovery steps.

Fixes: 48cf973cae33 ("pwm: rockchip: Avoid glitches on already running PWMs")
Fixes: 457f74abbed0 ("pwm: rockchip: Keep enabled PWMs running while probing")
Reported-by: Trent Piepho <tpiepho@gmail.com>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 31 +++++++++++++++----------------
 1 file changed, 15 insertions(+), 16 deletions(-)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index d2058138ce1e..f286a498b82c 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -289,6 +289,7 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 	struct rockchip_pwm_chip *pc;
 	struct resource *r;
 	u32 enable_conf, ctrl;
+	bool enabled;
 	int ret, count;
 
 	id = of_match_device(rockchip_pwm_dt_ids, &pdev->dev);
@@ -335,7 +336,8 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 	ret = clk_prepare_enable(pc->pclk);
 	if (ret) {
 		dev_err(&pdev->dev, "Can't enable APB clk: %d\n", ret);
-		goto err_clk;
+		clk_disable_unprepare(pc->clk);
+		return ret;
 	}
 
 	platform_set_drvdata(pdev, pc);
@@ -351,29 +353,26 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 		pc->chip.of_pwm_n_cells = 3;
 	}
 
-	ret = pwmchip_add(&pc->chip);
-	if (ret < 0) {
-		clk_unprepare(pc->clk);
-		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
-		goto err_pclk;
-	}
-
 	/* Keep the PWM clk enabled if the PWM appears to be up and running. */
 	enable_conf = pc->data->enable_conf;
 	ctrl = readl_relaxed(pc->base + pc->data->regs.ctrl);
-	if ((ctrl & enable_conf) != enable_conf)
+	enabled = ((ctrl & enable_conf) == enable_conf);
+	if (!enabled)
 		clk_disable(pc->clk);
 
 	clk_disable(pc->pclk);
 
-	return 0;
-
-err_pclk:
-	clk_disable_unprepare(pc->pclk);
-err_clk:
-	clk_disable_unprepare(pc->clk);
+	ret = pwmchip_add(&pc->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+		if (enabled)
+			clk_disable(pc->clk);
+		clk_unprepare(pc->clk);
+		clk_unprepare(pc->pclk);
+		return ret;
+	}
 
-	return ret;
+	return 0;
 }
 
 static int rockchip_pwm_remove(struct platform_device *pdev)
-- 
2.29.2