PC64: Get the timestap from the proper OF field

[breno.leitao_gmail.com]

Summary

After revision rS328534('PPC64: use hwref instead of cpuid'), FreeBSD on
powerpc64 virtual machine panics since it is unable to read the
timebase, showing the following error:

    
get-property for timebase-frequency on zero phandle
    
panic: Unable to determine timebase frequency!

With the change above, cpuref->cr_hwref does not contain the phandle
anymore, thus, it never reads the proper CPU entry in OF.

[imp]

So I have a memory of OF properties not being NUL terminated. If so, this code is wrong, though it might accidentally be right in some cases.

sys/powerpc/pseries/platform_chrp.c

296 ↗

(On Diff #38887)

Is buf NUL terminated?

303 ↗

(On Diff #38887)

Is buf NUL terminated?

[imp]

Turns out IEEE 1275 standard and successors all guarantee that text strings are 1 to 31 characters followed by a NUL byte, so my worry is bogus.

[breno.leitao_gmail.com]

Let me attach a new fix as proposed by Justin

[jhibbits]

Fix those two nits, otherwise looks good.

sys/powerpc/pseries/platform_chrp.c

294 ↗

(On Diff #39048)

cpus is not a boolean, you should use cpus == 0.

302 ↗

(On Diff #39048)

Same as above here.