Introduce framework to configure the multiplexed pins on boot.
Since the USART supprots RS-485 multidrop mode, it allows the
TX pins to float. However, for RS-232 operations, we don't
want these pins to float. Instead, they should be pulled up
to avoid mismatches. Linux does something similar when it
configures the TX lines. This implies that we also allow the
RX lines to float rather than be in the state they are left in
by the boot loader. Since they are input pins, I think that
this is the right thing to do.
Plus minor for our board.
address is in the userland address space. The proper thing is either to choose
a virtual address in the kernel address space beyond the KVA, or to use
pmap_mapdev().
number of banks, rows and columns the SDRAMC is programmed to access
to determine the RAM size for the board, rather than hard-wiring it to
be 32MB. My company's board with 64MB now probes correctly, as does
the KB9202 with only 32MB. This means that to detect the right memory
size, our boot loader must correctly initialize these values. This is
a fairly safe assumption because the boot loader has to initialize
SDRAM already, and it isn't really possible to change this register
after we've accessed SDRAM.
is a ARM920T based CPU with a bunch of built-in peripherals. The
inital import supports the SPI bus, the TWI bus (although iicbus
integration is not complete), the uarts, the system timer and the
onboard ethernet. Support for the Kwikbyte KB9202
(http://www.kwikbyte.com) board is also included, although there's no
reason why the 9200 and the 9201 wouldn't also work. Primitive
support for running under the skyeye emulator is also provided
(although skyeye's support for the AT91RM9200 is a little weak).
The code has been structured so that other members of Atmel's arm family can
be supported in the future. The AT91SAM9260 is not presently supported
due to lack of hardware. The arm7tdmi families are also not supported
becasue they lack an MMU.
Many thanks to cognet@ for his help and assistance in bringing up this
board. He did much of the vm work and wrote parts of the uart and
system timer code as well as the bus space implementation.
The system boots to single user w/o problem, although the serial
console is a little slow and the ethernet driver is still in flux.
This work was sponsored by Timing Solutions, Corporation. I am
grateful to their support of the FreeBSD project in this manner.
