K 10
svn:author
V 3
ian
K 8
svn:date
V 27
2017-03-08T18:53:32.054092Z
K 7
svn:log
V 714
Handle fifo size differences between older and newer revs of pl011 hardware.

Starting with rev 5 (which is inexplicably indicated by a version number
of '3' in the Peripheral ID register), the pl011 doubled the size of the
rx and tx fifos, to 32 bytes, so read the ID register and set the size
variables in the softc accordingly.

An interesting wrinkle in this otherwise-simple concept is that the
bcm2835 SoC, used in Raspberry Pi systems among others, has the rev 5
pl011 hardware, but somehow also has the older 16-byte fifos.  We check
the FDT data to see if the hardware is part of a bcm283x system and use
the smaller size if so.

Thanks to jchandra@ for pointing out that newer hardware has bigger fifos.

END