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

Wolfgang Denk
2004-03-23T21:38:04Z

In message <761C62B8-7757-11D8-A4C6-000393DBC2E8@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
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