[PATCH v3 4/4] arm64: dts: rockchip: Decrease emmc-phy's drive impedance on rk3399-puma

Christoph Muellner
2019-03-22T11:34:53Z

The RK3399-Q7 (Puma) requires 33 Ohm drive strength to ensure signal
integrity at HS-400 (200MHz clock, DDR signalling).

A repeated EMC testing run validates that this increase does not
negatively impact EMC compliance (emissions have ample distance to
the regulatory limits).

Signed-off-by: Christoph Muellner <christoph.muellner-SN7IsUiht6C/RdPyistoZJqQE7yCjDx5@public.gmane.org>
Signed-off-by: Philipp Tomsich <philipp.tomsich-SN7IsUiht6C/RdPyistoZJqQE7yCjDx5@public.gmane.org>
Tested-by: Jakob Unterwurzacher <jakob.unterwurzacher-SN7IsUiht6C/RdPyistoZJqQE7yCjDx5@public.gmane.org>
Tested-by: Klaus Goger <klaus.goger-SN7IsUiht6C/RdPyistoZJqQE7yCjDx5@public.gmane.org>
---
arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
index 0130b9f98c9d..4f75bb6b2f14 100644
--- a/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
+++ b/arch/arm64/boot/dts/rockchip/rk3399-puma.dtsi
@@ -146,6 +146,7 @@

&emmc_phy {
status = "okay";
+ drive-impedance-ohm = <33>;
};

&gmac {
--
2.11.0