linux-kernel - Re: [RCF PATCH,v2,2/2] pwm: imx: Configure output to GPIO in disabled state

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Message-ID: <20181107093355.e4n3irrnkybqsjvc@pengutronix.de>
Date:   Wed, 7 Nov 2018 10:33:55 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Vokáč Michal <Michal.Vokac@...ft.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Lukasz Majewski <l.majewski@...ess.pl>,
        Fabio Estevam <fabio.estevam@....com>,
        Lothar Waßmann <LW@...o-electronics.de>,
        kernel@...gutronix.de
Subject: Re: [RCF PATCH,v2,2/2] pwm:
 imx: Configure output to GPIO in disabled state

Hello Michal,

just to state it more explicitly, I think the following patch (not even
compile tested) is much preferable over your approach:

diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c
index 1d5242c9cde0..af88644b5efb 100644
--- a/drivers/pwm/pwm-imx.c
+++ b/drivers/pwm/pwm-imx.c
@@ -216,7 +216,14 @@ static int imx_pwm_apply_v2(struct pwm_chip *chip, struct pwm_device *pwm,
 			cr |= MX3_PWMCR_POUTC;
 
 		writel(cr, imx->mmio_base + MX3_PWMCR);
-	} else if (cstate.enabled) {
+	} else if (cstate.enabled && state->polarity == PWM_POLARITY_NORMAL) {
+		/*
+		 * When disabled in hardware the output pin goes to 0
+		 * independant of the polarity setting. The expectation of some
+		 * people however is that after disabling the pin goes to the
+		 * inactive level which isn't given for an inversed pwm, so
+		 * only disable for normal polarity.
+		 */
 		writel(0, imx->mmio_base + MX3_PWMCR);
 
 		clk_disable_unprepare(imx->clk_per);

I think it solves most if not all problems you want to address with the
pinctrl stuff.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |