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Date:   Wed, 28 Nov 2018 11:25:50 +0100
From:   Maxime Ripard <maxime.ripard@bootlin.com>
To:     Chen-Yu Tsai <wens@csie.org>
Cc:     Alexandre Belloni <alexandre.belloni@bootlin.com>,
        Alessandro Zummo <a.zummo@towertech.it>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        linux-arm-kernel@lists.infradead.org, linux-rtc@vger.kernel.org,
        linux-clk@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-sunxi@googlegroups.com
Subject: Re: [PATCH 09/15] clk: sunxi-ng: r40: Force LOSC parent to RTC LOSC
 output
Message-ID: <20181128102550.qsipssx67y3uexsr@flea>
References: <20181128093013.24442-1-wens@csie.org>
 <20181128093013.24442-11-wens@csie.org>
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On Wed, Nov 28, 2018 at 05:30:07PM +0800, Chen-Yu Tsai wrote:
> On the R40, in addition to a mux between the RTC's own RC oscillator and
> an external 32768 Hz crystal, which are muxed inside the RTC module, the
> CCU also has its own RC oscillator, which runs at around 2 MHz, and can
> be muxed with the LOSC output from the RTC. This muxed output is called
> "SYS 32K" in the module clock diagram, but otherwise referred to as the
> LOSC throughout the CCU documentation.
>=20
> The RC oscillator is not very accurate, even though it has an undocumented
> calibration function. We really want a precise clock at 32768 Hz,
> instead of something at around 32 KHz. This patch forces the SYS 32K
> clock to use the RTC output as its parent, and doesn't bother
> registering the internal oscillator nor a clock mux.
>=20
> Signed-off-by: Chen-Yu Tsai <wens@csie.org>

Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>

Maxime

--=20
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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