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From: Simon South <simon@simonsouth.net>
To: tpiepho@gmail.com, thierry.reding@gmail.com,
	u.kleine-koenig@pengutronix.de, robin.murphy@arm.com,
	lee.jones@linaro.org, heiko@sntech.de, bbrezillon@kernel.org,
	linux-pwm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-rockchip@lists.infradead.org
Cc: simon@simonsouth.net
Subject: [PATCH v3 7/7] pwm: rockchip: Enable clock before calling clk_get_rate()
Date: Wed, 23 Dec 2020 11:01:09 -0500
Message-ID: <58dc19f81bbf531d2921c6fb0018a5cc37dc9794.1608735481.git.simon@simonsouth.net> (raw)
In-Reply-To: <cover.1608735481.git.simon@simonsouth.net>

The documentation for clk_get_rate() in include/linux/clk.h states the
function's result is valid only for a clock source that has been
enabled. However, the Rockchip PWM driver uses this function in two places
to query the rate of a clock without first ensuring it is enabled.

Fix this by modifying rockchip_pwm_get_state() and rockchip_pwm_apply() so
they enable a device's PWM clock before querying its rate (in the latter
case, the querying is actually done in rockchip_pwm_config()) and disable
the clock again before returning.

Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Simon South <simon@simonsouth.net>
---
 drivers/pwm/pwm-rockchip.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index 02da7370db70..44425eeb4e81 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -72,6 +72,10 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	if (ret)
 		return;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return;
+
 	clk_rate = clk_get_rate(pc->clk);
 
 	tmp = readl_relaxed(pc->base + pc->data->regs.period);
@@ -90,6 +94,7 @@ static void rockchip_pwm_get_state(struct pwm_chip *chip,
 	else
 		state->polarity = PWM_POLARITY_NORMAL;
 
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 }
 
@@ -189,6 +194,10 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	if (ret)
 		return ret;
 
+	ret = clk_enable(pc->clk);
+	if (ret)
+		return ret;
+
 	pwm_get_state(pwm, &curstate);
 	enabled = curstate.enabled;
 
@@ -208,6 +217,7 @@ static int rockchip_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
 	}
 
 out:
+	clk_disable(pc->clk);
 	clk_disable(pc->pclk);
 
 	return ret;
-- 
2.29.2


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  parent reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-23 16:01 [PATCH v3 0/7] pwm: rockchip: Eliminate potential race condition when probing Simon South
2020-12-23 16:01 ` [PATCH v3 1/7] pwm: rockchip: Enable APB clock during register access while probing Simon South
2021-01-13  7:23   ` Uwe Kleine-König
2020-12-23 16:01 ` [PATCH v3 2/7] pwm: rockchip: rockchip_pwm_probe(): Remove superfluous clk_unprepare() Simon South
2021-01-13  7:31   ` Uwe Kleine-König
2020-12-23 16:01 ` [PATCH v3 3/7] pwm: rockchip: Replace "bus clk" with "PWM clk" Simon South
2021-01-13  7:33   ` Uwe Kleine-König
2020-12-23 16:01 ` [PATCH v3 4/7] pwm: rockchip: Eliminate potential race condition when probing Simon South
2021-01-13  7:37   ` Uwe Kleine-König
2020-12-23 16:01 ` [PATCH v3 5/7] pwm: rockchip: rockchip_pwm_probe(): Remove unneeded goto target Simon South
2021-01-13  7:38   ` Uwe Kleine-König
2020-12-23 16:01 ` [PATCH v3 6/7] pwm: rockchip: Enable PWM clock of probed device only if running Simon South
2021-01-13  7:50   ` Uwe Kleine-König
2021-01-14 15:22     ` Simon South
2020-12-23 16:01 ` Simon South [this message]
2021-01-13  7:54   ` [PATCH v3 7/7] pwm: rockchip: Enable clock before calling clk_get_rate() Uwe Kleine-König

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