[U-Boot-Users] Patch: Support for PQ27e (8247/48/71/72) chips and MPC8272ADS board

[Wolfgang Denk]

In message <761C62B8-7757-11D8-A4C6-000393DBC2E8 at motorola.com> you wrote:
> 
> I agree with only enabling ports that will be used.  I guess I would  
> expect the port to be used in Linux.  I'm working on an updated 2.6 SCC  
> uart driver and realized that I needed to enable the 2nd port in BCSR.   
> I had expected that u-boot would have already handled it.

The philosophy is to enable  and/or  initialize  only  those  devices
which are actually used by U-Boot itself. Even the network interfaces
get  initialized  only at the moment when you issue the first command
to access the network.

On the other hand a Linux device driver should assume  it  finds  the
device  in  an  unknown  random  (*)  state,  it  should  perform all
initialization it needs itself, and it should deinitialize the device
(if the driver should get unloaded) into an idle state.

(*) "random" is not completely random, of course - it  still  assumes
that  the device is well-behaving, i. e. that interrupts are disabled
etc.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
"When anyone says `theoretically,' they really mean `not really.'"
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