cvs commit: src/sys/dev/mii brgphy.c

John Polstra jdp at
Tue Mar 20 21:27:51 UTC 2007

Jung-uk Kim wrote:
> On Tuesday 20 March 2007 03:28 pm, John Polstra wrote:
>> Jung-uk Kim wrote:
>>> jkim        2007-03-19 23:17:39 UTC
>>>   FreeBSD src repository
>>>   Modified files:
>>>     sys/dev/mii          brgphy.c
>>>   Log:
>>>   Revert couple of changes from 1.51 and 1.52.  Reading link
>>> status with BMSR is okay for most of the chipsets but BCM5701 PHY
>>> does not seem to like it.
>> I'm not sure what you mean by "does not seem to like it", but did
>> you try reading the BMSR twice?  The link status bit is a latching
>> bit.  If you read the register once and it shows no link status,
>> that only means that at some point since you previously read the
>> register, link was lost.  It says nothing about the current status
>> of link.  The only way to find out the current status of link is to
>> read the register twice. The first read clears the latch, and the
>> second read reports the current status.  This is not specific to
>> the Broadcom chips.  It is standard across all PHYs.
> Believe me, I know that. ;-)  I was experimenting on brgphy.c some 
> time ago and discovered all of my Broadcom PHYs are not 'standard' 
> PHYs (in your definition), i.e., BMSR's link status bit is not 
> latching.

The Broadcom docs I have seen document the bit as latching.  Of course, 
the docs aren't necessarily correct. :-)


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