On Thu, 8 Sep 2005, Tommy Christensen wrote:
Besides, how long would you like to wait for network connectivity
after plugging in the cable? It is now lowered from [60-120] to
[0-60] seconds.
I now understood what the problem was, so I'll put it in words for
posterity: the Link Status bit of the MII Status register needs to be
read twice to first clear the error state (link bit=0) after which the
bit reports the actual value of the link. From the manual:
This bit has a latching function. A link failure causes the
bit to clear and remain clear until it has been read through
the management interface.
I tested this on a Tornado chip and it works as advertised (after link
is back up, first read gives 0x7829, the second 0x782d).
But I still don't agree with your solution: you are reading the Status
register twice in all cases, which is wrong. What you want is to read
it a second time only after the link was marked as down: a simple
check if bit 2 of the Status register is 0, in which case you issue
the second read. This still means that there will be 2 reads if the
link remains down, but at least there is only 1 read for the case
where the link is up and remains up.
Personally, I'd prefer the delay to be < 10 seconds.
If you sample every 60 seconds ? Teach Shannon how to do it ;-)
If you mean to reduce the sampling period, there is a very good reason
not to do it: these MDIO operations are expensive - it's a serial
protocol. vortex_timer() might do 2 (and with the discussed change -
3) of them - there are better things to do for the CPU than wait for
these I/O operations. Plus, vortex_timer() also disables the
interrupt...
The Tornado and at least some Cyclone chips support generating an
interrupt whenever the link changes, which can be used instead of
polling for link state. This feature is not used in the 3c59x driver
and could give you much less than 10 seconds accuracy - but you have
to code it. ;-)
--
Bogdan Costescu
IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: [email protected]
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