From: Sean Young <sean@mess.org>
To: "Thierry Reding" <thierry.reding@gmail.com>,
"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
"Florian Fainelli" <florian.fainelli@broadcom.com>,
"Ray Jui" <rjui@broadcom.com>,
"Scott Branden" <sbranden@broadcom.com>,
"Broadcom internal kernel review list"
<bcm-kernel-feedback-list@broadcom.com>
Cc: Sean Young <sean@mess.org>,
linux-pwm@vger.kernel.org, linux-rpi-kernel@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [PATCH v11] pwm: bcm2835: Allow PWM driver to be used in atomic context
Date: Wed, 20 Dec 2023 14:24:25 +0000 [thread overview]
Message-ID: <20231220142426.1275052-1-sean@mess.org> (raw)
clk_get_rate() may do a mutex lock. Fetch the clock rate once, and prevent
rate changes using clk_rate_exclusive_get().
Signed-off-by: Sean Young <sean@mess.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
---
drivers/pwm/pwm-bcm2835.c | 38 +++++++++++++++++++++++++++++---------
1 file changed, 29 insertions(+), 9 deletions(-)
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
index ab30667f4f95..307c0bd5f885 100644
--- a/drivers/pwm/pwm-bcm2835.c
+++ b/drivers/pwm/pwm-bcm2835.c
@@ -28,6 +28,7 @@ struct bcm2835_pwm {
struct device *dev;
void __iomem *base;
struct clk *clk;
+ unsigned long rate;
};
static inline struct bcm2835_pwm *to_bcm2835_pwm(struct pwm_chip *chip)
@@ -63,17 +64,11 @@ static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
{
struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
- unsigned long rate = clk_get_rate(pc->clk);
unsigned long long period_cycles;
u64 max_period;
u32 val;
- if (!rate) {
- dev_err(pc->dev, "failed to get clock rate\n");
- return -EINVAL;
- }
-
/*
* period_cycles must be a 32 bit value, so period * rate / NSEC_PER_SEC
* must be <= U32_MAX. As U32_MAX * NSEC_PER_SEC < U64_MAX the
@@ -88,13 +83,13 @@ static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
* <=> period < ((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate
* <=> period <= ceil((U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC/2) / rate) - 1
*/
- max_period = DIV_ROUND_UP_ULL((u64)U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC / 2, rate) - 1;
+ max_period = DIV_ROUND_UP_ULL((u64)U32_MAX * NSEC_PER_SEC + NSEC_PER_SEC / 2, pc->rate) - 1;
if (state->period > max_period)
return -EINVAL;
/* set period */
- period_cycles = DIV_ROUND_CLOSEST_ULL(state->period * rate, NSEC_PER_SEC);
+ period_cycles = DIV_ROUND_CLOSEST_ULL(state->period * pc->rate, NSEC_PER_SEC);
/* don't accept a period that is too small */
if (period_cycles < PERIOD_MIN)
@@ -103,7 +98,7 @@ static int bcm2835_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
writel(period_cycles, pc->base + PERIOD(pwm->hwpwm));
/* set duty cycle */
- val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * rate, NSEC_PER_SEC);
+ val = DIV_ROUND_CLOSEST_ULL(state->duty_cycle * pc->rate, NSEC_PER_SEC);
writel(val, pc->base + DUTY(pwm->hwpwm));
/* set polarity */
@@ -131,6 +126,13 @@ static const struct pwm_ops bcm2835_pwm_ops = {
.apply = bcm2835_pwm_apply,
};
+static void devm_clk_rate_exclusive_put(void *data)
+{
+ struct clk *clk = data;
+
+ clk_rate_exclusive_put(clk);
+}
+
static int bcm2835_pwm_probe(struct platform_device *pdev)
{
struct bcm2835_pwm *pc;
@@ -151,8 +153,26 @@ static int bcm2835_pwm_probe(struct platform_device *pdev)
return dev_err_probe(&pdev->dev, PTR_ERR(pc->clk),
"clock not found\n");
+ ret = clk_rate_exclusive_get(pc->clk);
+ if (ret)
+ return dev_err_probe(&pdev->dev, ret,
+ "fail to get exclusive rate\n");
+
+ ret = devm_add_action_or_reset(&pdev->dev, devm_clk_rate_exclusive_put,
+ pc->clk);
+ if (ret) {
+ clk_rate_exclusive_put(pc->clk);
+ return ret;
+ }
+
+ pc->rate = clk_get_rate(pc->clk);
+ if (!pc->rate)
+ return dev_err_probe(&pdev->dev, -EINVAL,
+ "failed to get clock rate\n");
+
pc->chip.dev = &pdev->dev;
pc->chip.ops = &bcm2835_pwm_ops;
+ pc->chip.atomic = true;
pc->chip.npwm = 2;
platform_set_drvdata(pdev, pc);
--
2.43.0
next reply other threads:[~2023-12-20 14:24 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-20 14:24 Sean Young [this message]
2023-12-20 16:06 ` [PATCH v11] pwm: bcm2835: Allow PWM driver to be used in atomic context Thierry Reding
2023-12-22 10:30 ` Uwe Kleine-König
2023-12-22 10:37 ` Sean Young
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