Hello Ezra,
On Sat, 10 Oct 2020 18:41:24 +0200 Ezra Buehler ezra@easyb.ch wrote:
I am running Debian buster (Linux 4.19.146) on a Synology DS214+ NAS (Marvell ARMADA XP). Unfortunately, I end up with random MAC addresses for the two Ethernet interfaces after boot. (Also with Debian sid, Linux 5.4.0.)
Since commit 8cc3e439ab92 ("net: mvneta: read MAC address from hardware when available") the mvneta Linux driver reads the MVNETA_MAC_ADDR_* registers when no MAC address is provided by the DT. In my case, only zeros are read, causing the driver to fall back to a random address. I was able to verify that the registers are correctly written by the bootloader by reading out the registers in the U-Boot prompt.
As a workaround, I now specify the MAC addresses in the DT. However, I would prefer not to do that. Also, it would be nice to get to the bottom of this.
Could it be, that for some reason, the clock of the MAC is removed either by U-Boot or Linux during boot?
I suspect you have the mvneta driver as a module ? If this is the case, then indeed, the MAC address is lost because Linux turns of all unused clocks at the end of the boot. When the driver is built-in, there is a driver adding a reference to the clock before all unused clocks are disabled. When the driver is compiled as a module, this does not happen. So indeed, the correct solution here is to have U-Boot pass the MAC address in the Device Tree.
Best regards,
Thomas Petazzoni