[U-Boot] [PATCH] rockchip: pinctrl: rk3399: add gmac io strength support

[Klaus Goger]

> On 20 Apr 2017, at 10:48, Dr. Philipp Tomsich <philipp.tomsich at theobroma-systems.com> wrote:
> 
>> On 20 Apr 2017, at 10:44, Kever Yang <kever.yang at rock-chips.com> wrote:
>> 
>> Hi Philipp,
>>> 
>>> 
>>> Do you know if this is required for all board designs?
>>> We have a total run length of less than 2cm to the KSZ9031 PHY and wondered about this ourselves—our testing has shown that with these small distances (and the PHY we use) the setting doesn’t seem to be required.
>> 
>> If your layout is very good, it might work without this patch, did you test with 1000M Ethernet on many boards?
>> With patch, we can keep the setting with kernel and make sure all the hardware able to work at 1000M mode.
>> The firefly-rk3399 and rockchip rk3399-evb can't work at 1000M Ethernet mode without this patch.
> 
> Yes, we have full GbE in U-Boot (without this change) across the entire board population of our initial batch.
> This is most likely due to the very short distance between the RK3399 and PHY (there isn’t really an alternative
> to having it close due to the size constraints of the module).

Just for completeness, Linux with default drive strength (&pcfg_pull_none) works on puma-rk3399 too.
Tested with iperf3 we get about 935Mbit with zero RX/TX errors.

Regards,
Klaus