GTMR errata work-around

[Joerg Sonnenberger <joerg%bec.de@localhost>]

Hello all,
we recently got a workaround for the A-008585 erratum on certain Cortex
variants. At the moment, it is enabled unconditionally, partially
because it is not known which boards/chips really need it. I'd be
interested to hear reports on the affected systems. Since a change to
use FDT to selectively enable it will be committed soon, now would be a
very good time to test.

You can check your system with "vmstat -e | grep gtmr":

armgtmr0 CNTV_TVAL write retry max       8    0 misc
armgtmr0 CNTV_CVAL read retry max        1    0 misc
armgtmr0 CNTVCT read retry max           5    0 misc
armgtmr0 CNTPCT read retry max           6    0 misc

The most interesting indicator is likely the first, CNTV_TVAL. That
value should not need a retry cycle as it should be read-only from the
chip perspective. A value larger than 1 is therefore likely an indicator
of the problem.

Joerg