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 <[email protected]>
Reviewed-by: Florian Fainelli <[email protected]>
---
drivers/pwm/pwm-bcm2835.c | 40 +++++++++++++++++++++++++++++----------
1 file changed, 30 insertions(+), 10 deletions(-)
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
index ab30667f4f95..e556ae300c82 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 */
@@ -151,16 +146,40 @@ 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");
+
+ pc->rate = clk_get_rate(pc->clk);
+ if (!pc->rate) {
+ clk_rate_exclusive_put(pc->clk);
+ 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);
ret = devm_pwmchip_add(&pdev->dev, &pc->chip);
- if (ret < 0)
+ if (ret < 0) {
+ clk_rate_exclusive_put(pc->clk);
return dev_err_probe(&pdev->dev, ret,
"failed to add pwmchip\n");
+ }
+
+ return 0;
+}
+
+static int bcm2835_pwm_remove(struct platform_device *pdev)
+{
+ struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
+
+ clk_rate_exclusive_put(pc->clk);
return 0;
}
@@ -197,6 +216,7 @@ static struct platform_driver bcm2835_pwm_driver = {
.pm = pm_ptr(&bcm2835_pwm_pm_ops),
},
.probe = bcm2835_pwm_probe,
+ .remove = bcm2835_pwm_remove,
};
module_platform_driver(bcm2835_pwm_driver);
--
2.43.0
Hello Sean,
On Mon, Dec 18, 2023 at 09:06:46AM +0000, Sean Young wrote:
> @@ -151,16 +146,40 @@ 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");
If Maxime didn't object to my series at
https://lore.kernel.org/linux-clk/[email protected]/,
I'd ask you to not do error checking here. With the objection I hesitate
to ask for that and just mention it.
> + pc->rate = clk_get_rate(pc->clk);
> + if (!pc->rate) {
> + clk_rate_exclusive_put(pc->clk);
> + 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);
>
> ret = devm_pwmchip_add(&pdev->dev, &pc->chip);
> - if (ret < 0)
> + if (ret < 0) {
> + clk_rate_exclusive_put(pc->clk);
> return dev_err_probe(&pdev->dev, ret,
> "failed to add pwmchip\n");
> + }
> +
> + return 0;
> +}
> +
> +static int bcm2835_pwm_remove(struct platform_device *pdev)
> +{
> + struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
> +
> + clk_rate_exclusive_put(pc->clk);
The ugly thing here is that now clk_rate_exclusive_put() happens before
pwmchip_remove(). Maybe register a devm cleanup which also gets rid of
the two clk_rate_exclusive_put() in probe's error path?
> return 0;
> }
> @@ -197,6 +216,7 @@ static struct platform_driver bcm2835_pwm_driver = {
> .pm = pm_ptr(&bcm2835_pwm_pm_ops),
> },
> .probe = bcm2835_pwm_probe,
> + .remove = bcm2835_pwm_remove,
Please use .remove_new
Best regards
Uwe
--
Pengutronix e.K. | Uwe Kleine-K?nig |
Industrial Linux Solutions | https://www.pengutronix.de/ |
Hello Uwe,
On Mon, Dec 18, 2023 at 10:31:36AM +0100, Uwe Kleine-K?nig wrote:
> On Mon, Dec 18, 2023 at 09:06:46AM +0000, Sean Young wrote:
> > + pc->rate = clk_get_rate(pc->clk);
> > + if (!pc->rate) {
> > + clk_rate_exclusive_put(pc->clk);
> > + 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);
> >
> > ret = devm_pwmchip_add(&pdev->dev, &pc->chip);
> > - if (ret < 0)
> > + if (ret < 0) {
> > + clk_rate_exclusive_put(pc->clk);
> > return dev_err_probe(&pdev->dev, ret,
> > "failed to add pwmchip\n");
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int bcm2835_pwm_remove(struct platform_device *pdev)
> > +{
> > + struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
> > +
> > + clk_rate_exclusive_put(pc->clk);
>
> The ugly thing here is that now clk_rate_exclusive_put() happens before
> pwmchip_remove().
Mixing devm with non-devm does lead to problems like this.
> Maybe register a devm cleanup which also gets rid of
> the two clk_rate_exclusive_put() in probe's error path?
That's good idea, I've done that in v10.
>
> > return 0;
> > }
> > @@ -197,6 +216,7 @@ static struct platform_driver bcm2835_pwm_driver = {
> > .pm = pm_ptr(&bcm2835_pwm_pm_ops),
> > },
> > .probe = bcm2835_pwm_probe,
> > + .remove = bcm2835_pwm_remove,
>
> Please use .remove_new
No longer needed in v10.
Sean