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rockchip: rk3399-puma: reduce sd card max-frequency to 40MHz

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Some SanDisk Ultra cards trigger intermittent errors on detection
resulting in an -EOPNOTSUPP, when running at 50MHz.

Waveform analysis suggest that the level shifters that are used on the
RK3399-Q7 module (for voltage translation between the on-module
voltages and the 3.3V required on the card-edge) don't handle clock
rates at or above 48MHz properly. This change reduces the maximum
frequency on the external SD-interface to 40MHz (for a safety margin
of 20%).

Reported-by: Jakob Unterwurzacher <jakob.unterwurzacher@theobroma-systems.com>
Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Christoph Muellner <christoph.muellner@theobroma-systems.com>
This commit is contained in:
Philipp Tomsich 2018-11-30 18:58:58 +01:00
parent ae66a0e1a2
commit 765246a18c
1 changed files with 1 additions and 1 deletions
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2
arch/arm/dts/rk3399-puma.dtsi
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@ -503,7 +503,7 @@
&sdmmc {
u-boot,dm-pre-reloc;
clock-frequency = <150000000>;
clock-freq-min-max = <100000 150000000>;
max-frequency = <40000000>;
supports-sd;
bus-width = <4>;
cap-mmc-highspeed;