[PATCH AUTOSEL 4.19 400/671] arm64: dts: renesas: ebisu: Remove renesas, no-ether-link property

[Sasha Levin <sashal@kernel.org>]

From: Takeshi Kihara <takeshi.kihara.df@renesas.com>

[ Upstream commit 90d4fa39d028f2e46c57c3d0e1b759e5287d98b7 ]

It is incorrect to specify the no-ether-link property for the AVB device on
the Ebisu board. This is because the property should only be used when a
board does not provide a proper AVB_LINK signal. However, the Ebisu board
does provide this signal.

As per 87c059e9c39d ("arm64: dts: renesas: salvator-x: Remove renesas,
no-ether-link property") this fixes a bug:

    Steps to reproduce:
    - start AVB TX stream (Using aplay via MSE),
    - disconnect+reconnect the eth cable,
    - after a reconnection the eth connection goes iteratively up/down
      without user interaction,
    - this may heal after some seconds or even stay for minutes.

    As the documentation specifies, the "renesas,no-ether-link" option
    should be used when a board does not provide a proper AVB_LINK signal.
    There is no need for this option enabled on RCAR H3/M3 Salvator-X/XS
    and ULCB starter kits since the AVB_LINK is correctly handled by HW.

    Choosing to keep or remove the "renesas,no-ether-link" option will have
    impact on the code flow in the following ways:
    - keeping this option enabled may lead to unexpected behavior since the
      RX & TX are enabled/disabled directly from adjust_link function
      without any HW interrogation,
    - removing this option, the RX & TX will only be enabled/disabled after
      HW interrogation. The HW check is made through the LMON pin in PSR
      register which specifies AVB_LINK signal value (0 - at low level;
      1 - at high level).

    In conclusion, the present change is also a safety improvement because
    it removes the "renesas,no-ether-link" option leading to a proper way
    of detecting the link state based on HW interrogation and not on
    software heuristic.

Fixes: 8441ef643d7d ("arm64: dts: renesas: r8a77990: ebisu: Enable EthernetAVB")
Signed-off-by: Takeshi Kihara <takeshi.kihara.df@renesas.com>
[simon: updated changelog]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
index 2bc3a4884b00..470c2a35a5af 100644
--- a/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
+++ b/arch/arm64/boot/dts/renesas/r8a77990-ebisu.dts
@@ -33,7 +33,6 @@
 &avb {
 	pinctrl-0 = <&avb_pins>;
 	pinctrl-names = "default";
-	renesas,no-ether-link;
 	phy-handle = <&phy0>;
 	phy-mode = "rgmii-txid";
 	status = "okay";
-- 
2.20.1