linux-kernel - [RFC 2/3] ARM: dts: Specify MSHC realistic clocks and use frequency scaling

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Date:	Mon, 12 Jan 2015 10:23:04 +0100
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Chris Ball <chris@...ntf.net>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mmc@...r.kernel.org, Kukjin Kim <kgene@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org
Cc:	Kyungmin Park <kyungmin.park@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [RFC 2/3] ARM: dts: Specify MSHC realistic clocks and use frequency
 scaling

Lower the dw_mmc host clock from 400 MHz to 100 MHz because there are a
lot of MMC errors above 100 MHz.

Enable frequency scaling to reduce energy consumption. In idle this
reduced energy consumption by 2.6% (from 119.5 mA to 116.4 mA).

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>
---
 arch/arm/boot/dts/exynos4412-trats2.dts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm/boot/dts/exynos4412-trats2.dts b/arch/arm/boot/dts/exynos4412-trats2.dts
index 29231b452643..21f1236ae979 100644
--- a/arch/arm/boot/dts/exynos4412-trats2.dts
+++ b/arch/arm/boot/dts/exynos4412-trats2.dts
@@ -558,7 +558,9 @@
 		non-removable;
 		card-detect-delay = <200>;
 		vmmc-supply = <&vemmc_reg>;
-		clock-frequency = <400000000>;
+		clock-frequency = <100000000>;
+		clock-freq-min-max = <400000 100000000>;
+		frequency-scaling;
 		samsung,dw-mshc-ciu-div = <0>;
 		samsung,dw-mshc-sdr-timing = <2 3>;
 		samsung,dw-mshc-ddr-timing = <1 2>;
-- 
1.9.1

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