Patch "pwm: sifive: Ensure the clk is enabled exactly once per running PWM" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    pwm: sifive: Ensure the clk is enabled exactly once per running PWM

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     pwm-sifive-ensure-the-clk-is-enabled-exactly-once-pe.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 158e4adeb675da673db4f78c85e40b87c73cdd54
Author: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
Date:   Thu Jul 21 12:31:28 2022 +0200

    pwm: sifive: Ensure the clk is enabled exactly once per running PWM
    
    [ Upstream commit ace41d7564e655c39f709a78c035188a460c7cbd ]
    
    .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 <u.kleine-koenig@xxxxxxxxxxxxxx>
    Tested-by: Emil Renner Berthing <emil.renner.berthing@xxxxxxxxxxxxx>
    Signed-off-by: Thierry Reding <thierry.reding@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/pwm/pwm-sifive.c b/drivers/pwm/pwm-sifive.c
index cc32f7ce09a6..1def1bc59240 100644
--- a/drivers/pwm/pwm-sifive.c
+++ b/drivers/pwm/pwm-sifive.c
@@ -230,6 +230,8 @@ static int pwm_sifive_probe(struct platform_device *pdev)
 	struct pwm_chip *chip;
 	struct resource *res;
 	int ret;
+	u32 val;
+	unsigned int enabled_pwms = 0, enabled_clks = 1;
 
 	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
 	if (!ddata)
@@ -260,6 +262,33 @@ 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);
@@ -282,7 +311,11 @@ 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;
 }
@@ -290,21 +323,16 @@ 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);