From: Boris Brezillon <boris.brezillon@free-electrons.com>
Date: Tue, 14 Jun 2016 09:13:13 +0000 (+0200)
Subject: UPSTREAM: pwm: rockchip: Avoid glitches on already running PWMs
X-Git-Tag: firefly_0821_release~419
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=370a8d95d44bd49bbe7ce2b8d23a761ad4c50ec8;p=firefly-linux-kernel-4.4.55.git

UPSTREAM: pwm: rockchip: Avoid glitches on already running PWMs

The current logic will disable the PWM clk even if the 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 the PWM is enabled to avoid any glitches.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
(commit 48cf973cae33488f84d7ab79a0f613383cff4de4)

Conflicts:
	drivers/pwm/pwm-rockchip.c

Change-Id: I75ffccd19c5244568fc0034d1585dac490296111
Signed-off-by: David Wu <david.wu@rock-chips.com>
---

diff --git a/drivers/pwm/pwm-rockchip.c b/drivers/pwm/pwm-rockchip.c
index dc785f023671..52592643f3a6 100644
--- a/drivers/pwm/pwm-rockchip.c
+++ b/drivers/pwm/pwm-rockchip.c
@@ -354,13 +354,13 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 		return ret;
 	}
 
-	ret = clk_prepare(pc->clk);
+	ret = clk_prepare_enable(pc->clk);
 	if (ret) {
 		dev_err(&pdev->dev, "Can't prepare pwm clk: %d\n", ret);
 		return ret;
 	}
 
-	ret = clk_prepare(pc->pclk);
+	ret = clk_prepare_enable(pc->pclk);
 	if (ret) {
 		dev_err(&pdev->dev, "Can't prepare pclk: %d\n", ret);
 		goto err_clk;
@@ -386,6 +386,12 @@ static int rockchip_pwm_probe(struct platform_device *pdev)
 		goto err_pclk;
 	}
 
+	/* Keep the PWM clk enabled if the PWM appears to be up and running. */
+	if (!pwm_is_enabled(pc->chip.pwms)) {
+		clk_disable(pc->pclk);
+		clk_disable(pc->clk);
+	}
+
 	return 0;
 
 err_pclk:
@@ -400,6 +406,22 @@ static int rockchip_pwm_remove(struct platform_device *pdev)
 {
 	struct rockchip_pwm_chip *pc = platform_get_drvdata(pdev);
 
+	/*
+	 * Disable the PWM clk before unpreparing it if the PWM device is still
+	 * running. This should only happen when the last PWM user left it
+	 * enabled, or when nobody requested a PWM that was previously enabled
+	 * by the bootloader.
+	 *
+	 * FIXME: Maybe the core should disable all PWM devices in
+	 * pwmchip_remove(). In this case we'd only have to call
+	 * clk_unprepare() after pwmchip_remove().
+	 *
+	 */
+	if (pwm_is_enabled(pc->chip.pwms)) {
+		clk_disable(pc->pclk);
+		clk_disable(pc->clk);
+	}
+
 	clk_unprepare(pc->pclk);
 	clk_unprepare(pc->clk);