RE: [net-next,PATCH v2] enetc: Increase eMDIO MDC rate to 2.5 MHz

[Wei Fang]

> >> Clark helped measure the MDC rate on the 95 EVK board this morning,
> >> and the result was 644KHz, which is consistent with the theoretical
> >> value. The scope's accuracy or other factors may be causing you to
> >> observe a rate of 558kHz.
> >
> > That 644 kHz and 558 kHz differs too much to be an equipment
> > miscalibration / misuse.
> 
> For the sake of completeness, the MX95 B0 I have on my desk now prints this in
> SM:
> 
>  >$ clock.r
> ...
> 097: busnetcmix           =  on,  133333333Hz
> 098: enet                 =  on,  666666666Hz
> 099: enetphytest200m      =  on,   24000000Hz
> 100: enetphytest500m      =  on,   24000000Hz
> 101: enetphytest667m      =  on,   24000000Hz
> 102: enetref              =  on,  250000000Hz
> 103: enettimer1           =  on,   24000000Hz
> 
> And the cycle time of MDC is 1.8ms , which is some 550 kHz .

The enet clock is the source of NETC system clock, and there is a 1/2
divisor inside the NETCMIX, so the NETC system clock is 333 MHz.
So the MDC clock should be 644 KHz, the frequency measured by
Clark in the attachment is indeed 644kHz.

Attachment: mdc_clock_on_95_b0.png
Description: mdc_clock_on_95_b0.png