[ECOS] Serial Driver in Redboot vs HAL

[Doris, Thomas]

I'm working on a port of the iq80310 HAL to an Xscale based processor,
primarily to provide RedBoot functionality, but I want to ensure that we
provide a correct HAL for general use. Currently I'm running the code on a
s/w simulated model of the processor, which supports UART I/O but no other
external devices. My confusion is this: the hal_diag.c implements a UART
driver through the cyg_plf_serial_* functions, which seems to be all that
RedBoot requires for console I/O. However there is a directory
packages/devs/serial/arm/iq80310 which contains cdl stuff which states that
the iq80310 serial driver is to be based on the generic 16X5X serial driver.
I am assuming that the hal_diag serial code is used for redboot and
diagnostic code, while the "proper" driver under packages/devs/serial is
used by the real i/o library in real eCos applications. Any
information/clarification on the official position on this would be
appreciated.

Secondly, my simulator does not support any external devices such as flash
or network. When running RedBoot, it is the case that the code in
packages/redboot/current/src/flash does not handle this well - a brief
inspection of the function do_flash_init will reveal that the way it sets
the variable __flash_init is not very useful, it sets it to true even when
the flash initialisation fails, it seems that there should be a similar
variable which indicates whether the initialization has been successful or
not - if flash init fails it would make sense to prevent the subsequent
invokation of flash related functions. From our persepective the bootloader
software has the additional responsibility for manufacturing diagnostics -
as each board rolls off the line it is powered up and the board level
devices are tested; the bootloader should report any critical errors which
may indicate manufacturing defects to the operator. If the flash device is
defective, then it is likely that Redboot will not load, in which case a RAM
based RedBoot load will be downloaded through a JTAG port, and it should
then report the flash defect, and continue to test other devices. 

Similarly, the edb7xxx cs8900 ethernet driver will hang forever waiting for
an "initialization OK" message from the CS8900 device. It would seem that
the right thing to do here is to have an upper limit timeout so that failure
to initialise could be detected and booting continue - however I am not sure
what the policy is on having a dependency between an ethernet driver and a
hal timer. Any advice on this would be appreciated.

Tom Doris