Subject: Re: Caching in the MPC107, linux 2.6

From: Adrian Cox <[email-masked]>
Date: Mon, 15 Mar 2004 22:42:13 +0000

On Mon, 2004-03-15 at 20:38, Tom Rini wrote:

> Actually, I was thinking that having an extra nop there on the !SMP &&
> !(745x && MPC107) case wouldn't hurt much / at all, and having this
> feature bit be done unconditionally.  But in cpu_setup_6xx.S we would
> compare the host bridge vendor / device ID to that of an mpc107.  Or am
> I not thinking right, and doing that comparison at that time would be a
> bad idea?  If so, I can live with it being an unconditional option, iff
> it's only required when MPC10X_STORE_GATHERING is enabled.

The only problem I see is that in cpu_setup_6xx.S we can't yet do the
config cycles to tell that it is an MPC107. Luckily, all MPC10x boards
that I know of require an explicit platform selection option.

I made my patch depend on CONFIG_MPC10X_BRIDGE, instead of
CONFIG_MPC10X_STORE_GATHERING, because I'm in the middle of porting
other MPC107 drivers from kernel 2.4 to 2.6.

An extra nop won't hurt, but there is a performance cost to
_PAGE_COHERENT which we should avoid unless necessary.

- Adrian Cox
http://www.humboldt.co.uk/

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