Some rockchip SoCs like the RK3399 and RK3328 exhibit an issue
where tx checksumming does not work with packets larger than 1498.
The default Programmable Buffer Length for TX in these GMAC's is
not suitable for MTUs higher than 1498. The workaround is to disable
TX offloading with 'ethtool -K eth0 tx off rx off' causing performance
impacts as it disables hardware checksumming.
This patch sets snps,txpbl to 0x4 which is a safe number tested ok for
the most popular MTU value of 1500.
For reference, see https://lkml.org/lkml/2019/4/1/1382.
Signed-off-by: Carlos de Paula <me@carlosedp.com>
Link: https://lore.kernel.org/r/20200218221040.10955-1-me@carlosedp.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: David Bauer <mail@david-bauer.net>
Hardware
--------
RockChip RK3328 ARM64 (4 cores)
1GB DDR4 RAM
2x 1000 Base-T
3 LEDs (LAN / WAN / SYS)
1 Button (Reset)
Micro-SD slot
USB 2.0 Port
Installation
------------
Uncompress the OpenWrt sysupgrade and write it to a micro SD card using
dd.
MAC-address
-----------
The vendor code supports reading a MAC address from an EEPROM connected
via i2c0 of the SoC. The EEPROM (address 0x51) should contain the MAC
address in binary at offset 0xfa. However, my two units didn't come with
such an EEPROM soldered on. The EEPROM should be placed between the SoC
and the GPIO pins on the board. (U10)
Generating rendom MAC addresses works around this issue. Otherwise, all
boards running the same image have identical MAC addresses.
Signed-off-by: David Bauer <mail@david-bauer.net>
