Best way to define flash partitions for an MPC8248

Kumar Gala galak at kernel.crashing.org
Wed Feb 14 04:32:50 EST 2007


On Feb 13, 2007, at 9:08 AM, Laurent Pinchart wrote:

> Hi everybody,
>
> I'm running Linux 2.6.20 on an MPC8248 using arch/ppc/.
>
> The system flash is divided in 5 partitions, which are currently  
> defined in
> both U-Boot and in the Linux kernel (hardcoded in platform specific  
> code in
> arch/ppc/platforms/). This is error prone, as modifying partition  
> information
> requires a change to the U-Boot environment variables and a  
> recompilation of
> the Linux kernel.
>
> I would like to get rid of partition data in the kernel. I found 3  
> ways for
> the Linux kernel to get those data from elsewhere:
>
> - command line parsing (using the mtdparts argument)
> - redboot partition table parsing
> - OF device tree (drivers/mtd/maps/physmap_of.c)
>
> What is the best suited method ? I don't really like the redboot  
> partition
> table, is I haven't found any way to write it from U-Boot. Do I  
> need to
> switch to arch/powerpc/ to use the OF device tree ? If so, is it  
> possible
> today for the MPC8248 processor, or is it still badly supported in
> arch/powerpc/ ? Last but not least, is it possible to change the OF  
> device
> tree from U-Boot at runtime to resize partitions ?

You'll have to switch to arch/powerpc for using the of device tree  
parsing.  I believe the 8248/827x are supported under arch/powerpc at  
this point.

I don't believe its possible to change the OF device tree at runtime  
currently, you'll have to add code to u-boot to do that.  U-boot does  
very little with the device tree beyond setting it up and filling in  
some values that are needed (memory sizes, frequencies, etc.)

- k



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