linux-kernel - [PATCH v5 25/46] pwm: sti: avoid glitches on already running PWMs

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Message-Id: <1459368249-13241-26-git-send-email-boris.brezillon@free-electrons.com>
Date:	Wed, 30 Mar 2016 22:03:48 +0200
From:	Boris Brezillon <boris.brezillon@...e-electrons.com>
To:	Thierry Reding <thierry.reding@...il.com>,
	linux-pwm@...r.kernel.org
Cc:	Mike Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
	Mark Brown <broonie@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Kamil Debski <k.debski@...sung.com>, lm-sensors@...sensors.org,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-input@...r.kernel.org, Bryan Wu <cooloney@...il.com>,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	linux-leds@...r.kernel.org,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
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	Joachim Eastwood <manabian@...il.com>,
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	Daniel Vetter <daniel.vetter@...el.com>,
	Jani Nikula <jani.nikula@...ux.intel.com>,
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	Boris Brezillon <boris.brezillon@...e-electrons.com>
Subject: [PATCH v5 25/46] pwm: sti: avoid glitches on already running PWMs

The current logic will disable the PWM clk even if a PWM was left
enabled by the bootloader (because it's controlling a critical device
like a regulator for example).
Keep the PWM clk enabled if at least one PWM is enabled to avoid any
glitches.

Signed-off-by: Boris Brezillon <boris.brezillon@...e-electrons.com>
---
 drivers/pwm/pwm-sti.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/pwm/pwm-sti.c b/drivers/pwm/pwm-sti.c
index 0fbca94..bea1d17 100644
--- a/drivers/pwm/pwm-sti.c
+++ b/drivers/pwm/pwm-sti.c
@@ -343,7 +343,7 @@ static int sti_pwm_probe(struct platform_device *pdev)
 	struct sti_pwm_compat_data *cdata;
 	struct sti_pwm_chip *pc;
 	struct resource *res;
-	int ret;
+	int i, ret;
 
 	pc = devm_kzalloc(dev, sizeof(*pc), GFP_KERNEL);
 	if (!pc)
@@ -394,7 +394,7 @@ static int sti_pwm_probe(struct platform_device *pdev)
 		return -EINVAL;
 	}
 
-	ret = clk_prepare(pc->clk);
+	ret = clk_prepare_enable(pc->clk);
 	if (ret) {
 		dev_err(dev, "failed to prepare clock\n");
 		return ret;
@@ -412,6 +412,19 @@ static int sti_pwm_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	/*
+	 * Keep the PWM clk enabled if some PWMs appear to be up and
+	 * running.
+	 */
+	for (i = 0; i < pc->chip.npwm; i++) {
+		struct pwm_state pstate;
+
+		pwm_get_state(&pc->chip.pwms[i], &pstate);
+		if (pstate.enabled)
+			clk_enable(pc->clk);
+	}
+	clk_disable(pc->clk);
+
 	platform_set_drvdata(pdev, pc);
 
 	return 0;
-- 
2.5.0