On Fri, Jan 06, 2017 at 06:42:24AM +0100, Yegor Yefremov wrote:

On Fri, Jan 6, 2017 at 12:25 AM, Russell King - ARM Linux
[off-list ref] wrote:

quoted

Another concern with this patch is that the existing phylib "set_eee"
code is horribly buggy - it just translates the modes from userspace
into the register value and writes them directly to the register with
no validation.  So it's possible to set modes in the register that the
hardware doesn't support, and have them advertised to the link partner.

I have a patch which fixes that, restricting (as we do elsewhere) the
advert according to the EEE supported capabilities retrieved from the
PCS - maybe the problem here is that the PCS doesn't support support
EEE in 1000baseT mode?

Out of interest, which PHY is used on this platform?

On the SolidRun boards, they're using AR8035, and have suffered this
occasional link drop problem.  What has been found is that it seems to
be to do with the timing parameters, and it seemed to only be 1000bT
that was affected.  I don't remember off hand exactly which or what
the change was they made to stabilise it though, but I can probabily
find out tomorrow.

I have different boards with am335x and AR8035 and we had occasional
link drop with both 100 and 1000 speeds.

AR8035 has "Smart EEE", which is a PHY specific thing... it's not
entirely 802.3 compliant as it doesn't involve the MAC.

The Smart EEE control registers are in the PCS MMD - some of this
is from people's memories:

- 0x805b is the TX wakeup timer.  Lower 8 bits for 100base-Tx and
  upper 8 bits for 1000base-T.

- 0x805c and 0x805d.
  The LPI timer is 24 bit, with the lower 16 bits in 0x805c and the
  upper 8 in 0x805d.  0x805d bit 8 appears to be the Smart EEE enable bit.

What was found was setting the 1000base-T wakeup timer to the same as
the 100base-Tx avoided the problems we were seeing, which was only
with 1000base-T.  (Whether that's because 100base-Tx hasn't been as well
tested, I don't know.)  SR ended up with 0x1717 in 0x805b.

I'd suggest playing around with that register to see if extending the
wakeup time has any beneficial effect.

Also, I suspect Smart EEE shouldn't be enabled if you have an EEE
capable MAC (in which case 0x805d bit 8 should be clear.)  I think,
however, it defaults to enabled.

-- 
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