Hi Sasha,
On Mon, Jun 22, 2020 at 2:52 PM Sasha Levin sashal@kernel.org wrote:
This is a note to let you know that I've just added the patch titled
ARM: dts: meson: Switch existing boards with RGMII PHY to "rgmii-id"to the 5.7-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: arm-dts-meson-switch-existing-boards-with-rgmii-phy-.patch and it can be found in the queue-5.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
this patch has another dependency on upstream commit 9308c47640d515 ("net: stmmac: dwmac-meson8b: add support for the RX delay configuration") which itself depends on a few other commits unless you are also planning to backport more changes (I would have to make a detailed list and also reserve some time for testing) I suggest to drop this patch from 5.7, 5.4 and 4.19
some more information below.
[...]
Previously we did not know that these boards used an RX delay. We assumed that setting the TX delay on the MAC side It turns out that these boards also require an RX delay of 2ns (verified on Odroid-C1, but the u-boot code uses the same setup on both boards). Ethernet only worked because u-boot added this RX delay on the MAC side.
configuring the RX delay on the MAC side is only supported since 5.8-rc1 prior to that we relied on the bootloader to do "the right thing"
The 4ns TX delay was also wrong and the result of using an unsupported RGMII TX clock divider setting. This has been fixed in the driver with commit bd6f48546b9cb7 ("net: stmmac: dwmac-meson8b: Fix the RGMII TX delay on Meson8b/8m2 SoCs").
changing the TX delay could be done in a separate patch, but it still wouldn't fully fix Ethernet without the RX delay configuration (see above)
Thank you! Martin