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

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Date:   Sat, 05 Jan 2019 17:46:18 -0300
From:   Paul Cercueil <paul@...pouillou.net>
To:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
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

Hi Uwe,

On Sat, Jan 5, 2019 at 4:42 PM, Uwe Kleine-König 
<u.kleine-koenig@...gutronix.de> wrote:
> 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?

No, it does not change the behaviour.

>>  @@ -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.

You pointed it, indeed; but I won't change it until I can verify that 
the
behaviour is correct (which does not seem to be the case even if I leave
this bit cleared). Besides, this is the TCU patchset, fixes and patches
unrelated to the TCU don't belong here.

> Best regards
> Uwe

Kind regards,
-Paul