ARM: dts: microsom-ar8035: MDIO pad must be set open drain

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This patch is important for the MicroSOM implementation due to the
following details -

1. VIH of the Atheros phy is 1.7V.
2. NVCC_ENET which is the power domain of the MDIO pad is driven by the
   PHY's LDO (i.e. either 1.8v or 2.5v).
3. The MicroSOM implements an onbouard 1.6kohm pull up to 3.3v (R3000).

In the case the PHY's LDO was 1.8v then there would be only a 100mV
margin for the signal to be acknowledged as high (1.8v-1.7v).
Due to that setting the pad as an open drain will let the 1.6kohm pull
that signal high to 3.3 that assures enough margins to the PHY to be
acked as '1' logic.

Signed-off-by: Rabeeh Khoury <rabeeh@solid-run.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

...

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Rabeeh Khoury 2014-08-23 10:11:21 +01:00 • committed by Shawn Guo

parent 962af86121

commit bf8147208e

1 changed files with 1 additions and 1 deletions

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arch/arm/boot/dts/imx6qdl-microsom-ar8035.dtsi

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