Hi Trent,
> -----Original Message-----
> From: Trent Piepho <tpiepho@xxxxxxxxxx>
> Sent: Tuesday, May 14, 2019 8:40 PM
> To: linux-snps-arc@xxxxxxxxxxxxxxxxxxx
> Cc: Trent Piepho <tpiepho@xxxxxxxxxx>; Alexey Brodkin <abrodkin@xxxxxxxxxxxx>; Vineet Gupta
> <vgupta@xxxxxxxxxxxx>
> Subject: [PATCH] ARC: [hsdk] Use rgmii-id mode for ethernet phy
>
> If internal delays are desired on the RGMII link, "rgmii-id" should be
> used as the phy-mode rather than "rgmii" .
>
> This dts has properties to set the delay values, but they are ignored.
> I suspect this is a mistake.
>
> While the driver should disable delay based on the current DT, it does
> not, and instead leaves the PHY in the pin strapping default. Which is
> usually to have delays very close to the unused values the hsdk DT.
> Which is why the phy would work even if the delays in the DT are
> ignored.
Thanks for this patch!
Indeed there might very well be something incomplete in that .dts
as I didn't know all those details.
I did check and Micrel KSZ9031 Gigabit PHY on HSDK supports on-chip delay.
That's what its datasheet says:
------------------->8------------------
RGMII Timing Supports On-Chip Delay According to RGMII Version 2.0,
with Programming Options for External Delay and Making Adjustments
and Corrections to TX and RX Timing Paths.
------------------->8------------------
And with proposed change I don't see any regressions so far, which is good.
Still a couple of questions:
1. How did you spot this problem?
2. With some Ethernet cards (especially 1Gb ones) on the other end we do see
from time to time auto-negotiation takes that much time that
udhcpc fails to get a lease because 3 discovery packets sent in
a row get lost since link is not established (i.e. > 5 seconds).
Do you think if it has something to do with that particular issue?
Unfortunately I cannot reproduce this behavior right now so cannot
verify it myself.
-Alexey
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