On Tue, 2008-01-29 at 10:26 -0600, Scott Wood wrote: > On Mon, Jan 28, 2008 at 11:55:20PM +0000, Bryan O'Donoghue wrote: > > You mean that arch/powerpc/boot/mpc8xx.c mpc8xx_set_clocks is supposed > > to be adding this field ? > > Yes. Or u-boot, if you're not using the bootwrapper/cuImage.
Indeed - I have some patches to send to the u-boot mailing list to cover manipulation of the "fsl,cpm-brg" "clock-frequency" entry. The previously sent patch will allow Linux to print stuff out the UART will the default brgclk - from a uImage and is the field that a future u-boot patchset would want to manipulate in order to tell Linux about the brgclk it should have. I should be a bit clearer about that... > > > 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 > > In that case, u-boot needs to add that property. See above. > > dtc -O -o adder875-uboot.dtb arch/powerpc/boot/dts/adder875-uboot.dtb > > You'll want to use the -p option to add some extra space for u-boot to > use. Interesting - the u-boot end of this patch is something I'm still messing about with ... but, the addition of the default brgclk to the Linux dts is a useful addition - and AFAICT will be needed to allow a bootloader to manipulate the dts so that Linux will get the right brgclk. > > cpm_uart depends on "fsl,cpm-brg" and a field called "clock-frequency" > > > > as I understand it that's > > > > fsl,cpm-brg > > |_clock-frequency > > > > whereas mpc8xx_set_clocks seems to add > > > > /soc/cpm/brg > > |_clock-frequency > > The fsl,cpm-brg refers to the compatible property, not the node name. Indeed and the get_brgclk does a find_compatible() lookup of some sort... so I think that means this is the right field to add to allow a bootloader to manipulate the brgclk ... it's what the other stuff in u-boot for the mpc8xxx stuff does, so it follows to do the same thing for 8xx too. > > 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... > > And it's zero, meaning that you still need u-boot or the bootwrapper to > fill in the correct value. Indeed - I'm hoping I won't have too much trouble getting those patches applied... _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
