On 19/03/24 21:05, Andrew Davis wrote:
On 3/11/24 5:44 AM, Chintan Vankar wrote:
On 31/01/24 21:06, Andrew Davis wrote:
On 1/31/24 4:14 AM, Chintan Vankar wrote:
Add alias for the MCU CPSW2G port to enable Linux to fetch MAC Address
for the port directly from U-Boot.
Could you explain *how* this alias allows Linux to fetch a MAC
address from U-Boot? Sounds like we are doing something hacky here..
Using "probe_daughtercards()" function U-Boot parses MAC addresses from
EEPROM, then it internally calls "eth_env_set_enetaddr_by_index()"
function which stores these MAC addresses into environment variables
ethaddr, eth1addr, eth2addr and so on based on number of ports.
U-Boot loads DTB during boot process, and it calls
"fdt_fixup_ethernet()" function, which uses environment variables to
update MAC addresses of ethernet ports as specified in the aliases
section.
So maybe a better question would by why does it need to use aliases
for this?
Since "probe_daughtercards()" in U-Boot is implemented in a way that
it gets the MAC addresses fromm EEPROM and "fdt_fixup_ethernet()"
function configures MAC addresses for the ethernet ports as specified
in aliases section.
Why can't Linux fetch the MAC from efuses the same way U-Boot does,
Linux can fetch the MAC address from efuses if "ti,syscon-efuse"
property is enabled.
Then let's do it this way always.
Yes, Linux reads MAC addresses from efuse this way only, but the
functionality of Linux getting the MAC addresses from EEPROM is
not implemented.
what happens if I don't use U-Boot to boot?
If you don't use U-Boot to boot then the equivalent of
"probe_daughtercards()" has to be implemented which is currently
missing.
Or we just let Linux fetch it instead of implementing that function
in all the possible bootloaders. This would also remove a DTB fixup.
Those fixups should be avoided if at all possible.
Yes, we can let Linux fetch MAC addresses, but right now the Ethernet
driver in Linux can only fetch MAC addresses from "EFUSE" and not from
"EEPROM", and since the functionality to fetch MAC addresses from
"EEPROM" is implemented in U-Boot we are utilizing it.
Andrew
Andrew
---
arch/arm64/boot/dts/ti/k3-j784s4-evm.dts | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm64/boot/dts/ti/k3-j784s4-evm.dts
b/arch/arm64/boot/dts/ti/k3-j784s4-evm.dts
index f34b92acc56d..b74f7d3025de 100644
--- a/arch/arm64/boot/dts/ti/k3-j784s4-evm.dts
+++ b/arch/arm64/boot/dts/ti/k3-j784s4-evm.dts
@@ -27,6 +27,7 @@ aliases {
mmc1 = &main_sdhci1;
i2c0 = &wkup_i2c0;
i2c3 = &main_i2c0;
+ ethernet0 = &mcu_cpsw_port1;
};
memory@80000000 {
