[U-Boot] [PATCH] net: fec: Avoid MX28 bus sync issue

[Hector Palacios]

Hi Marek,

On 07/15/2013 02:30 PM, Marek Vasut wrote:
> Dear Hector Palacios,
>
>> Hi Marek,
>>
>> On 07/12/2013 06:48 PM, Marek Vasut wrote:
>>>>   [...]
>>>>
>>>> but I found something:
>>>> It is very strange that the timeouts appear always after transferring
>>>> between 20 and 24 MiB. So I thought maybe it was not an issue with the
>>>> size of the file or the number of packets received, but instead a timed
>>>> issue (an issue that happens after some period of time). I checked, and
>>>> in fact the timeouts occur exactly 10 seconds after running the tftp
>>>> command. I verified that this is what is happening by adding a
>>>> udelay(100000) at fec_send(). In this case, the timeout also occurs
>>>> after 10 seconds, but due to the delay, I have transferred only a few
>>>> Kbytes.
>>>
>>> Holy moly!
>>>
>>>> I tried to change different timeout related constants at tftp.c but
>>>> still the issue happens after 10s.
>>>> It's like if, after these 10 seconds, the PHY lost the link or
>>>> something. Really odd. Does it tell you anything?
>>>
>>> LAN8720 phy, right? Try implementing something like [1], by clearing the
>>> EDPWRDOWN bit , the PHY will never enter low-power mode. It's just a
>>> simple PHY register RMW which you can stick somewhere into the PHY
>>> net/phy/smsc.c code.
>>>
>>> [1]
>>> https://kernel.googlesource.com/pub/scm/linux/kernel/git/djbw/dmaengine/+
>>> /b629820d18fa65cc598390e4b9712fd5f83ee693%5E!/#F0
>>
>> No, my PHY is a Micrel KSZ8031RNLI.
>>
>> The hint about the PHY possibly going to power down mode is interesting but
>> I checked the PHY registers and EDPD mode (Energy Detect Power Down) is
>> off, at least before running the tftp command. Power Down mode is off too,
>> so unless these are somehow enabled during the TFTP process, this is not
>> what's happening.
>
> OK, makes sense.
>
>> The sniffer shows that the TFTP server simply stops sending data packets. I
>> can see however the target sending several times the ACK packet to the
>> last received data packet. This would point to the TFTP server (as Albert
>> suggested), but the fact is the problem occurs with different TFTP servers
>> (I tried three different servers) and it does not happen with an old v2009
>> U-Boot using the same target.
>
> Can you try running "dcache off" command before running the TFTP transfer? Does
> it still behave like this?
>
> You might need to define #define CONFIG_CMD_CACHE for this to work.

Sourcery!
It's not that it works with dcache off, I found something even more strange:
The way I reproduce this issue is by setting the 'bootcmd' to 'dboot ${loadaddr} 
file100M'. When you set the 'bootcmd' like this:

	setenv bootcmd tftp ${loadaddr} file100M

this eventually expands to

	bootcmd=tftp 0x42000000 file100M

So this is the command that runs automatically after the bootdelay.
I just discovered that if instead of letting the auto boot run, I press a key to stop 
the auto boot and run the command by hand (either running 'boot' or typing the command 
'tftp 0x42000000 file100M'), the tftp transfer works perfectly.
On the other hand, if I do the same but use the environment variable ${loadaddr}, i.e. 
'tftp ${loadaddr} file100M'. It will stop after 10 seconds.

And to make things funnier I just reproduced this issue on the MX28EVK using the imx 
U-Boot custodian tree at commit a3f170cdbf7ae0bd24c94c2f46725699bbd69f05. That 
discards being a platform issue.
@Fabio: could you manually run the command 'tftp ${loadaddr} file100M' in your EVK?
If it doesn't fail, could you try running it again after playing with the environment 
(setting/printing some variables).
As I said, this issue appeared with different TFTP servers and is independent of 
whether the dcache is or not enabled.

Best regards,
--
Hector Palacios