svn commit: r314917 - head/sys/dev/uart

[Rodney W. Grimes]

[ Charset UTF-8 unsupported, converting... ]
> Author: ian
> Date: Wed Mar  8 18:53:32 2017
> New Revision: 314917
> URL: https://svnweb.freebsd.org/changeset/base/314917
> 
> Log:
>   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.

The chip compiler probably has a parameter to set fifo depth,
this would normally be independent of the IP revision.


-- 
Rod Grimes                                                 rgrimes at freebsd.org