[U-Boot] [PATCH] Add CONFIG_GMAC_TX_DELAY=4 for OlinuXino Lime2

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 16-03-16 09:32, Michael Haas wrote:
> On 03/15/2016 07:09 PM, Karsten Merker wrote:
>> On Tue, Mar 15, 2016 at 06:41:39AM +0100, Michael Haas wrote:
>>
>>> This change is required to get GBIT Ethernet to work
>>> reliably on my board. Without CONFIG_GMAC_TX_DELAY=4, the connection
>>> suffers severe packet loss and SSH becomes unusable.
>>>
>>> --- 192.168.1.1 ping statistics ---
>>> 100 packets transmitted, 100 received, 0% packet loss, time 19842ms
>>> rtt min/avg/max/mdev = 0.260/0.334/0.527/0.038 ms
>>>
>>> I have also tried CONFIG_GMAC_TX_DELAY=3, which still
>>> yielded 11-13% packet loss.
>> Hello,
>>
>> unfortunately this change doesn't solve the gigabit issues
>> on my LIME2 - it even seems to make them worse on my board.
>>
>>
>> Could you perhaps try netbooting a kernel with your LIME2?
>> I would be interested in knowing whether that works on your
>> board (with CONFIG_GMAC_TX_DELAY=0/4).
>>
>>
> Hello Karsten,
>
> I just tried netbooting the debian installer: it didn't work, just as
> you said.
>
> Even worse: I noticed I had not installed my patched u-boot at all when
> I ran the ping test above! With my patch, the kernel would not download
> at all.
>
> So the patch is wrong and I'm sorry for having wasted everyone's time here.
>
> I won't give up yet, however. The fact still stands that at some point,
> I was able to use GBit Ethernet
> without any issues in Linux, possibly after a warm reboot.

Interesting, if you can reproduce things working better after a warm reboot,
try dumping the reg which gets modified by modifying ONFIG_GMAC_TX_DELAY,
note that reg has RX_DELAY bits too, maybe we need to tweak those.

Although a warm reboot typically only preserves settings outside of the soc,
so if a warm reboot fixes things int may be that whatever you're warm rebooting
from (I would assume some vendor image) is setting some things differently
in the phy.

Regards,

Hans


>
> For (my) future reference, I used these commands:
>
> --
> setenv bootargs console=ttyS0,115200 rootwait panic=10
> setenv autoload no
> dhcp
> setenv serverip 192.168.1.170
> tftpboot ${scriptaddr} /debian-installer/armhf/tftpboot.scr
> source ${scriptaddr}
> --
>
> I'll be playing around with the value a bit more to find the "best"
> value for netbooting from a cold state, then try to get it
> to work within Linux itself. Perhaps there are also some clock adjusts
> to be done from within the DTS.
>
> Sorry again!
>
> Michael
>