[U-Boot-Users] Uboot config doubts

[Wolfgang Denk]

In message <b92b327b0608301030p672bd5ana2889c99dd297963 at mail.gmail.com> you wrote:
> 
> I have a few questions about u-boot, and would appreciate if any of
> you guys can answer them for me.
> 
> i) What does CFG_HZ mean? Is it the number of timer interrupts every

It's the number of ticks per second. For U-Boot, this is 1000.

> second, or is it the 'maximum' number of timer ticks each second.
> Basically, I mean for a 10MHz timer, should CFG_HZ be 10,000,000 or
> can it be some number like 1000 if we program the timer register to be
> 10,000.

CFG_HZ shall be always set to 1000. [Note that there are a few incom-
plete/broken ports which use other settings. Please ignore these.]

> ii) I am seeing a few configuration files, where 'USE_920T_MMU' is
> set. As I understand, uboot does not use mmu. Is this define some kind
> of legacy code or do I know something wrong? Does uboot use MMU?

The MMU can be used for many different things. In most  cases  people
think of virtual memory whan they say "use the MMU", and this is what
U-Boot does NOT do.

Other possible uses may include making certain  memory  ranges  (un-)
cachable, etc. On some boards U-Boot uses the MMU for such purposes.

> iii) Do we need to define CONFIG_ARM920T if we are using ARM920T, some
> config files have done that, in my opinion, it is redundant.

Yes, you do have to define the correct CPU type in your board  config
file.

Best regards,

Wolfgang Denk

-- 
Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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