Re: [Linuxptp-users] recvmsg tx timestamp failed: Resource temporarily unavailable

[Richard C. <ric...@gm...>]

On Sat, Feb 09, 2013 at 04:13:08PM +0530, Rayagond Kokatanur wrote:
> 
> What is max_adj value ? Is it a maximum clock frequency connect to my
> MAC/PTP ?

No.

It is maximum adjustment (in parts per billion) tolerated by your
clock. If your clock can accept an adjustment 0.1%, then max_adj
will be 1000000.

> Whenever ptp4l calls .adjfreq, it passes either +/1 .max_adj frequency to
> .adjfreq api, why ?

Because the servo is trying to steer the clock at the maximum possible
rate. Probably your time stamps are messed up.

> 2> DEFAULT_ADDEND = 0xF0000029
> 
> What is this magic number ? 

The ixp featues a frequency compenstated clock, with input clock at
66 MHz. Every input clock, the addend is accumulated into a 32 bit
register. When that register overflows, it produces one clock tick at
the nominal frequency of 62.5 MHz. Changing the addend makes the clock
go faster or slower.

> Is it calculated based on max_adj frequency
> value ?

No, it is the other way round.

HTH,
Richard