Re: [PATCH 02/19] bootwrapper: Set -msoft-float and assembler target options.

["Mark A. Greer" <mgreer@mvista.com>]

On Tue, Mar 13, 2007 at 01:53:09PM +1100, Paul Mackerras wrote:

Many of these are really mine to answer...

> Scott Wood writes:
> > Without the assembler target option, the assembler will use the old
> > dedicated mftb/mftbu instructions, rather than mfspr.  This causes the
> > boot to hang on e500, which doesn't have the dedicated instructions.
> 
> I see mftb being used for udelay in util.S, and udelay being used in
> serial_edit_cmdline in serial.c.  It's somewhat bogus that we just
> hard-code an assumed timebase frequency in util.S, and also bogus that

The timebase stuff was a straight copy from arch/ppc/boot/common/util.S.
I agree that its a bogus and should be fixed.

> we get command line editing for serial consoles but not for OF
> consoles (why should they be different?).

IIRC, a few of us talked about that on IRC way back.  The consensus
was that you would just change it with OF.  I added editing for non-OF
(should really be any fw that doesn't pass in an updated dtb (i.e.,
anything but OF and the new u-boot)) because, the cmdline would be
coming from the dtb embedded in the zImage (or from builtin_cmdline).
To change it, you have to find the dts, change it, and run 'wrapper'
(or run a pgm to set builtin_cmdline).  Seems like a lot to do for
a quick, temporary cmdline edit.

Its easy enough to add for OF, if you think its worth it.  I lack the OF
knowledge to do so though.

> It looks to me like we should at least make the platform code provide
> udelay (or mdelay), possibly with the aid of a helper function.

Agreed.

> We
> should also consider whether the command-line editing is generally
> useful, or not, and whether the function to do it should be made more
> generic.

IMHO, it is very useful if you have fw that doesn't update the dtb for
you (i.e., OF and u-boot).  Don't know if it makes sense for OF and/or
u-boot.

Mark