linux-kernel - Re: [RFC PATCH v3 2/2] pwm: imx: Configure output to GPIO in disabled state

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Message-ID: <20190124104435.e6paqwcuz3hizwnv@pengutronix.de>
Date:   Thu, 24 Jan 2019 11:44:35 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Michal Vokáč <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>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [RFC PATCH v3 2/2] pwm: imx: Configure output to GPIO in
 disabled state

On Thu, Jan 24, 2019 at 11:12:12AM +0100, Michal Vokáč wrote:
> On 24.1.2019 10:22, Uwe Kleine-König wrote:
> > I think it might be beneficial to allow (or require) that disable acts
> > immediately. But this is not how it used to be and in my discussion with
> > Thierry (IIRC) he required to complete the currently running period.
> 
> I am confused here. IFAIK it always used to be that:
> 
> 	pwm_apply_state(pwm, { .enabled = 0 });
> 
> immediately stops the PWM with:
> 
> 	writel(0, imx->mmio_base + MX3_PWMCR);
> 
> regardless of the period (for pwm-imx).

Then is is a bug since forever (well, or a fact that resulted from the
intended semantic not being documented and the driver author not caring
or knowing better).

Best regards
Uwe

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