[6/7] pwm: sifive: Ensure the clk is enabled exactly one per running PWM

Commit Message

Uwe Kleine-König July 21, 2022, 10:31 a.m. UTC

.apply() assumes the clk to be for a given PWM iff the PWM is enabled.
So make sure this is the case when .probe() completes. And in .remove()
disable the according number of times.

This fixes a clk enable/disable imbalance, if some PWMs are already running
at probe time.

Fixes: 9e37a53eb051 (pwm: sifive: Add a driver for SiFive SoC PWM)
Signed-off-by: Uwe Kleine-König <[e-mail]>
---
 drivers/pwm/pwm-sifive.c | 46 ++++++++++++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 9 deletions(-)

Comments

Uwe Kleine-König July 21, 2022, 8:45 p.m. UTC | #1

Hello,

[dropped Yash Shah from Cc, their email address bounces]

While browsing the list of open patches in patchwork, I noticed a typo:

$Subject ~= s/one/once/

@Thierry: Assuming you are otherwise happy with this patch, should I
resend for this typo, or do you fixup while applying it?

Thanks
Uwe

Thierry Reding July 28, 2022, 5:10 p.m. UTC | #2

On Thu, Jul 21, 2022 at 10:45:22PM +0200, Uwe Kleine-König wrote:
> Hello,
> 
> [dropped Yash Shah from Cc, their email address bounces]
> 
> While browsing the list of open patches in patchwork, I noticed a typo:
> 
> $Subject ~= s/one/once/
> 
> @Thierry: Assuming you are otherwise happy with this patch, should I
> resend for this typo, or do you fixup while applying it?

I've fixed this up while applying, thanks.

Thierry

Patch

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index 34d23d56fa25..da40ade0ebdf 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -216,6 +216,8 @@  static int pwm_sifive_probe(struct platform_device *pdev)
 	struct pwm_sifive_ddata *ddata;
 	struct pwm_chip *chip;
 	int ret;
+	u32 val;
+	unsigned int enabled_pwms = 0, enabled_clks = 1;
 
 	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
 	if (!ddata)
@@ -242,6 +244,33 @@  static int pwm_sifive_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	val = readl(ddata->regs + PWM_SIFIVE_PWMCFG);
+	if (val & PWM_SIFIVE_PWMCFG_EN_ALWAYS) {
+		unsigned int i;
+
+		for (i = 0; i < chip->npwm; ++i) {
+			val = readl(ddata->regs + PWM_SIFIVE_PWMCMP(i));
+			if (val > 0)
+				++enabled_pwms;
+		}
+	}
+
+	/* The clk should be on once for each running PWM. */
+	if (enabled_pwms) {
+		while (enabled_clks < enabled_pwms) {
+			/* This is not expected to fail as the clk is already on */
+			ret = clk_enable(ddata->clk);
+			if (unlikely(ret)) {
+				dev_err_probe(dev, ret, "Failed to enable clk\n");
+				goto disable_clk;
+			}
+			++enabled_clks;
+		}
+	} else {
+		clk_disable(ddata->clk);
+		enabled_clks = 0;
+	}
+
 	/* Watch for changes to underlying clock frequency */
 	ddata->notifier.notifier_call = pwm_sifive_clock_notifier;
 	ret = clk_notifier_register(ddata->clk, &ddata->notifier);
@@ -264,7 +293,11 @@  static int pwm_sifive_probe(struct platform_device *pdev)
 unregister_clk:
 	clk_notifier_unregister(ddata->clk, &ddata->notifier);
 disable_clk:
-	clk_disable_unprepare(ddata->clk);
+	while (enabled_clks) {
+		clk_disable(ddata->clk);
+		--enabled_clks;
+	}
+	clk_unprepare(ddata->clk);
 
 	return ret;
 }
@@ -272,21 +305,16 @@  static int pwm_sifive_probe(struct platform_device *pdev)
 static int pwm_sifive_remove(struct platform_device *dev)
 {
 	struct pwm_sifive_ddata *ddata = platform_get_drvdata(dev);
-	bool is_enabled = false;
 	struct pwm_device *pwm;
 	int ch;
 
 	for (ch = 0; ch < ddata->chip.npwm; ch++) {
 		pwm = &ddata->chip.pwms[ch];
-		if (pwm->state.enabled) {
-			is_enabled = true;
-			break;
-		}
+		if (pwm->state.enabled)
+			clk_disable(ddata->clk);
 	}
-	if (is_enabled)
-		clk_disable(ddata->clk);
 
-	clk_disable_unprepare(ddata->clk);
+	clk_unprepare(ddata->clk);
 	pwmchip_remove(&ddata->chip);
 	clk_notifier_unregister(ddata->clk, &ddata->notifier);