PATCH[1/1] 8xx: Add clock-frequency to .dts brg entries

Bryan O'Donoghue bodonoghue at
Tue Jan 29 10:55:20 EST 2008

On Mon, 2008-01-28 at 09:50 -0600, Scott Wood wrote:
> On Mon, Jan 28, 2008 at 01:53:11AM +0000, Bryan O'Donoghue wrote:
> > cpm_uart_core has a dependency on fsl,cpm-brg/clock-frequency, this
> > means that a .dts that uses the cpm uart driver needs to supply a
> > clock-frequency entry for get_brgfreq to return a meaningful number.
> > 
> > Included is a patchset which adds the correct brgclk to the adder port -
> > @ 50Mhz and also adds an entry for mpc885ads - which I've noticed is
> > missing a clock-frequency entry.
> It's not missing -- it's added by the bootwrapper.
> -Scott


You mean that arch/powerpc/boot/mpc8xx.c mpc8xx_set_clocks is supposed
to be adding this field ? 

I see arch/powerpc/boot/wrapper.a has a reference to the function but -
and this time I've checked all documentation - there's no mention of how
to use this library at all... it _looks_ to me like this isn't being
linked in any way.

It for sure is nowhere in the uImage - and I've taken the preferred
route of making a uImage with .dtb - genreated from adder875-uboot.dts

dtc -O -o adder875-uboot.dtb arch/powerpc/boot/dts/adder875-uboot.dtb

cpm_uart depends on "fsl,cpm-brg" and a field called "clock-frequency"

as I understand it that's


whereas mpc8xx_set_clocks seems to add


So unless I'm not understanding the structure of the tree - possible - I
don't see how /soc/cpm/brg => clock-frequency could /possibly/ satisfy
get_brgfreq in fsl_soc.c

If there's something other then making a uImage and dtb and booting
these from u-boot that I'm supposed to be doing here ... it'd help if
you could say..

Otherwise in order to get the UART working using a uImage + dbt I've
found it necessary to add this field to the .dts....

mpc866ads.dts - also has a "fsl,cpm-brg" => clock-frequency entry in 

linux/arch/powerpc/boot/dts/mpc866ads.dts - and to me this looks like
the correct approach for get_brgfreq to function properly...

What do you think ?

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