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From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Stephen Boyd <sboyd@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>
Cc: linux-pwm@vger.kernel.org, Artur Rojek <contact@artur-rojek.eu>,
	Mathieu Malaterre <malat@debian.org>,
	linux-kernel@vger.kernel.org,
	Paul Cercueil <paul@crapouillou.net>,
	od@zcrc.me, Thierry Reding <thierry.reding@gmail.com>,
	kernel@pengutronix.de, linux-clk@vger.kernel.org
Subject: Re: About rounding in the clk framework [Was: Re: [PATCH 4/7] pwm: jz4740: Improve algorithm of clock calculation]
Date: Mon, 21 Dec 2020 14:57:58 +0100	[thread overview]
Message-ID: <20201221135758.edgskzkyyrw4lcx7@pengutronix.de> (raw)
In-Reply-To: <20200414092412.scsl6sekikc2tsv5@pengutronix.de>

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Hello,

On Tue, Apr 14, 2020 at 11:24:12AM +0200, Uwe Kleine-König wrote:
> Hello Stephen, hello Michael,
> 
> On Wed, Feb 12, 2020 at 08:29:11AM +0100, Uwe Kleine-König wrote:
> > Can you please explain what is the reason why clk_round_rate_up/down()
> > is a bad idea? Would it help to create a patch that introduces these
> > functions to get the discussion going?
> 
> I didn't get any feedback on my mail. Are you to busy working on more
> important stuff? Is the answer so obvious that you don't consider it
> worth your time to answer?
> 
> Looking a bit through the code I see there are two callbacks hwclks can
> provide to implement rounding (determine_rate and round_rate). The docs
> for both use the term "return the closes rate actually supported". Does
> that mean "round-closest" is already the official policy and other
> strategies in lowlevel drivers are a bug?

Feedback here would be really appreciated. I intend to unify the rounding
behaviour of PWMs to always round down. If there was a similar
constraint for clks, some corner cases might be a bit simpler.

Looking forward to read about your thoughts,
Uwe

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

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  reply	other threads:[~2020-12-21 14:00 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-09 12:30 [PATCH 0/7] pwm: jz4740: Driver update Paul Cercueil
2019-08-09 12:30 ` [PATCH 1/7] pwm: jz4740: Obtain regmap from parent node Paul Cercueil
2019-08-09 16:51   ` Uwe Kleine-König
2019-08-09 17:04     ` Paul Cercueil
2019-08-12  6:18       ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 2/7] pwm: jz4740: Use clocks from TCU driver Paul Cercueil
2019-08-09 16:55   ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 3/7] pwm: jz4740: Drop dependency on MACH_INGENIC Paul Cercueil
2019-08-09 16:41   ` Uwe Kleine-König
2019-08-09 21:40     ` Paul Cercueil
2019-08-12  6:09       ` Uwe Kleine-König
2019-08-09 12:30 ` [PATCH 4/7] pwm: jz4740: Improve algorithm of clock calculation Paul Cercueil
2019-08-09 17:05   ` Uwe Kleine-König
2019-08-09 17:14     ` Paul Cercueil
2019-08-12  6:15       ` Uwe Kleine-König
2019-08-12 20:43         ` Paul Cercueil
2019-08-12 21:48           ` Uwe Kleine-König
2019-08-12 22:25             ` Paul Cercueil
     [not found]             ` <1565648183.2007.3@crapouillou.net>
2019-08-13  5:27               ` Uwe Kleine-König
2019-08-13 11:01                 ` Paul Cercueil
2019-08-13 12:33                   ` Uwe Kleine-König
2019-08-13 12:47                     ` Paul Cercueil
2019-08-13 14:09                       ` Uwe Kleine-König
2019-08-14 16:10                         ` Paul Cercueil
2019-08-14 17:32                           ` Uwe Kleine-König
2019-10-21 12:47                             ` Paul Cercueil
2020-02-12  7:29                               ` About rounding in the clk framework [Was: Re: [PATCH 4/7] pwm: jz4740: Improve algorithm of clock calculation] Uwe Kleine-König
2020-04-14  9:24                                 ` Uwe Kleine-König
2020-12-21 13:57                                   ` Uwe Kleine-König [this message]
2019-08-09 12:30 ` [PATCH 5/7] pwm: jz4740: Allow selection of PWM channels 0 and 1 Paul Cercueil
2019-08-09 12:30 ` [PATCH 6/7] pwm: jz4740: Make PWM start with the active part Paul Cercueil
2019-08-09 17:10   ` Uwe Kleine-König
2019-08-09 17:33     ` Paul Cercueil
2019-08-12  5:55       ` Uwe Kleine-König
2019-08-12 20:50         ` Paul Cercueil
2019-08-12 21:58           ` Uwe Kleine-König
2019-09-20 22:52             ` Thierry Reding
2019-08-09 12:30 ` [PATCH 7/7] pwm: jz4740: document known limitations Paul Cercueil

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