[PATCH v2] arm64: dts: imx8mn-var-som: fix PHY detection bug by adding deassert delay

[Shawn Guo]

On Mon, May 01, 2023 at 01:05:32PM -0400, Hugo Villeneuve wrote:
> From: Hugo Villeneuve <hvilleneuve at dimonoff.com>
> 
> While testing the ethernet interface on a Variscite symphony carrier
> board using an imx8mn SOM with an onboard ADIN1300 PHY (EC hardware
> configuration), the ethernet PHY is not detected.
> 
> The ADIN1300 datasheet indicate that the "Management interface
> active (t4)" state is reached at most 5ms after the reset signal is
> deasserted.
> 
> The device tree in Variscite custom git repository uses the following
> property:
> 
>     phy-reset-post-delay = <20>;
> 
> Add a new MDIO property 'reset-deassert-us' of 20ms to have the same
> delay inside the ethphy node. Adding this property fixes the problem
> with the PHY detection.
> 
> Note that this SOM can also have an Atheros AR8033 PHY. In this case,
> a 1ms deassert delay is sufficient. Add a comment to that effect.
> 
> Fixes: ade0176dd8a0 ("arm64: dts: imx8mn-var-som: Add Variscite
> VAR-SOM-MX8MN System on Module")
> 
> Signed-off-by: Hugo Villeneuve <hvilleneuve at dimonoff.com>

Applied, thanks!