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Commit 30a3636f authored by Uwe Kleine-König's avatar Uwe Kleine-König Committed by Greg Kroah-Hartman
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pwm: sifive: Reduce time the controller lock is held 



[ Upstream commit 0f02f491b786143f08eb19840f1cf4f12aec6dee ]

The lock is only to serialize access and update to user_count and
approx_period between different PWMs served by the same pwm_chip.
So the lock needs only to be taken during the check if the (chip global)
period can and/or needs to be changed.

Signed-off-by: default avatarUwe Kleine-König <u.kleine-koenig@pengutronix.de>
Tested-by: default avatarEmil Renner Berthing <emil.renner.berthing@canonical.com>
Signed-off-by: default avatarThierry Reding <thierry.reding@gmail.com>
Stable-dep-of: 334c7b13d383 ("pwm: sifive: Always let the first pwm_apply_state succeed")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 62462a5b

drivers/pwm/pwm-sifive.c

+5 −3
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ 


struct pwm_sifive_ddata {

	struct pwm_chip	chip;

	struct mutex lock; /* lock to protect user_count */

	struct mutex lock; /* lock to protect user_count and approx_period */

	struct notifier_block notifier;

	struct clk *clk;

	void __iomem *regs;
@@ -78,6 +78,7 @@ static void pwm_sifive_free(struct pwm_chip *chip, struct pwm_device *pwm) 
	mutex_unlock(&ddata->lock);

}



/* Called holding ddata->lock */

static void pwm_sifive_update_clock(struct pwm_sifive_ddata *ddata,

				    unsigned long rate)

{
@@ -166,7 +167,6 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm, 
		return ret;

	}



	mutex_lock(&ddata->lock);

	cur_state = pwm->state;

	enabled = cur_state.enabled;
@@ -185,14 +185,17 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm, 
	/* The hardware cannot generate a 100% duty cycle */

	frac = min(frac, (1U << PWM_SIFIVE_CMPWIDTH) - 1);



	mutex_lock(&ddata->lock);

	if (state->period != ddata->approx_period) {

		if (ddata->user_count != 1) {

			mutex_unlock(&ddata->lock);

			ret = -EBUSY;

			goto exit;

		}

		ddata->approx_period = state->period;

		pwm_sifive_update_clock(ddata, clk_get_rate(ddata->clk));

	}

	mutex_unlock(&ddata->lock);



	writel(frac, ddata->regs + PWM_SIFIVE_PWMCMP0 +

	       pwm->hwpwm * PWM_SIFIVE_SIZE_PWMCMP);
@@ -202,7 +205,6 @@ static int pwm_sifive_apply(struct pwm_chip *chip, struct pwm_device *pwm, 


exit:

	clk_disable(ddata->clk);

	mutex_unlock(&ddata->lock);

	return ret;

}