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

[Marek Vasut <marex@denx.de>]

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.

> Many times, though not always, after the timeout occurs, I cancel with
> CTRL+C and run the tftp command again, and then the file downloads
> completely.
> The PHY is my usual suspect...

Dang :-(

Best regards,
Marek Vasut