linux-kernel - Re: [PATCH v9 12/27] pwm: jz4740: Use regmap from TCU driver

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Date:   Sat, 5 Jan 2019 20:42:26 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Jonathan Corbet <corbet@....net>, linux-pwm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-watchdog@...r.kernel.org, linux-mips@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH v9 12/27] pwm: jz4740: Use regmap from TCU driver

On Thu, Dec 27, 2018 at 07:13:04PM +0100, Paul Cercueil wrote:
> The ingenic-timer "TCU" driver provides us with a regmap, that we can
> use to safely access the TCU registers.
> 
> While this driver is devicetree-compatible, it is never (as of now)
> probed from devicetree, so this change does not introduce a ABI problem
> with current devicetree files.

Does it change behaviour? If so, how?

> @@ -113,26 +117,37 @@ static int jz4740_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>  
>  	jz4740_pwm_disable(chip, pwm);
>  
> -	jz4740_timer_set_count(pwm->hwpwm, 0);
> -	jz4740_timer_set_duty(pwm->hwpwm, duty);
> -	jz4740_timer_set_period(pwm->hwpwm, period);
> +	/* Set abrupt shutdown */
> +	regmap_update_bits(jz4740->map, TCU_REG_TCSRc(pwm->hwpwm),
> +			   TCU_TCSR_PWM_SD, TCU_TCSR_PWM_SD);

I think I already pointed that out before: abrupt mode is wrong. If
.apply is called with a new set of parameters the currently running
period with the old values is expected to complete before the new values
take effect.

Best regards
Uwe

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