diff mbox series

[v3,2/3] pwm: bcm2835: allow pwm driver to be used in atomic context

Message ID c826281c0ceab8ce8fcc453a5ce777444349ff9a.1697534024.git.sean@mess.org (mailing list archive)
State New, archived
Headers show
Series [v3,1/3] pwm: make it possible to apply pwm changes in atomic context | expand

Commit Message

Sean Young Oct. 17, 2023, 9:17 a.m. UTC 
clk_get_rate() may do a mutex lock. Since the clock rate cannot change on
an rpi, simply fetch it once.

Signed-off-by: Sean Young <sean@mess.org>
---
 drivers/pwm/pwm-bcm2835.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

Comments

Stefan Wahren Oct. 18, 2023, 3 p.m. UTC | #1 
Hi Sean,

Am 17.10.23 um 11:17 schrieb Sean Young:
> clk_get_rate() may do a mutex lock. Since the clock rate cannot change on
> an rpi, simply fetch it once.
the driver changes looks good to me, but could you please adapt the
commit message to your recent changes.

Best regards
>
> Signed-off-by: Sean Young <sean@mess.org>
> ---
>
Sean Young Oct. 19, 2023, 11:19 a.m. UTC | #2 
On Wed, Oct 18, 2023 at 05:00:23PM +0200, Stefan Wahren wrote:
> Hi Sean,
> 
> Am 17.10.23 um 11:17 schrieb Sean Young:
> > clk_get_rate() may do a mutex lock. Since the clock rate cannot change on
> > an rpi, simply fetch it once.
> the driver changes looks good to me, but could you please adapt the
> commit message to your recent changes.

Yes, the commit message needs fixing. Thanks for pointing that out.


Sean
diff mbox series

Patch

diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
index bdfc2a5ec0d69..bd636ac1c5074 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 */
@@ -156,18 +151,32 @@  static int bcm2835_pwm_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ret = clk_rate_exclusive_get(pc->clk);
+	if (ret)
+		goto add_fail;
+
+	pc->rate = clk_get_rate(pc->clk);
+	if (!pc->rate) {
+		dev_err(pc->dev, "failed to get clock rate\n");
+		ret = -EINVAL;
+		goto rate_fail;
+	}
+
 	pc->chip.dev = &pdev->dev;
 	pc->chip.ops = &bcm2835_pwm_ops;
+	pc->chip.atomic = true;
 	pc->chip.npwm = 2;
 
 	platform_set_drvdata(pdev, pc);
 
 	ret = pwmchip_add(&pc->chip);
 	if (ret < 0)
-		goto add_fail;
+		goto rate_fail;
 
 	return 0;
 
+rate_fail:
+	clk_rate_exclusive_put(pc->clk);
 add_fail:
 	clk_disable_unprepare(pc->clk);
 	return ret;
@@ -179,6 +188,7 @@  static void bcm2835_pwm_remove(struct platform_device *pdev)
 
 	pwmchip_remove(&pc->chip);
 
+	clk_rate_exclusive_put(pc->clk);
 	clk_disable_unprepare(pc->clk);
 }