[U-Boot] [PATCH] arm: vf610: move device tree after kernel image

[Tom Rini]

On Wed, Oct 14, 2015 at 09:05:33AM -0700, Stefan Agner wrote:
> Hi Tom,
> 
> On 2015-10-14 05:39, Tom Rini wrote:
> > On Tue, Oct 13, 2015 at 11:11:45PM -0700, Stefan Agner wrote:
> > 
> >> Since the device tree relocation is disabled (fdt_high set to
> >> 0xffffffff), U-Boot keeps the device tree at its load address
> >> 0x81000000. The kernel uncompresses itself to 0x80008000 by
> >> default, hence this limits the maximum (uncompressed) kernel
> >> size to somewhat below 16MiB, otherwise the device tree gets
> >> overwritten by the kernel data...
> >>
> >> Move the device tree load address to 0x84000000 to avoid that
> >> the device tree being overwritten by the kernel.
> >>
> >> Signed-off-by: Stefan Agner <stefan at agner.ch>
> >> ---
> >>  include/configs/vf610twr.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/include/configs/vf610twr.h b/include/configs/vf610twr.h
> >> index 324ba8f..1d15f35 100644
> >> --- a/include/configs/vf610twr.h
> >> +++ b/include/configs/vf610twr.h
> >> @@ -129,7 +129,7 @@
> >>  	"fdt_high=0xffffffff\0" \
> >>  	"initrd_high=0xffffffff\0" \
> >>  	"fdt_file=vf610-twr.dtb\0" \
> >> -	"fdt_addr=0x81000000\0" \
> >> +	"fdt_addr=0x84000000\0" \
> >>  	"boot_fdt=try\0" \
> >>  	"ip_dyn=yes\0" \
> >>  	"mmcdev=" __stringify(CONFIG_SYS_MMC_ENV_DEV) "\0" \
> > 
> > OK, this is all wrong :(  Please take a look at
> > include/configs/ti_armv7_common.h and DEFAULT_LINUX_BOOT_ENV (and the
> > giant comment block explaining the values).
> 
> This default environment is quite old, and according to the log it came
> from Timesys/Freescales initial BSP.
> 
> The end of the DDR is commonly used for the second Cortex-M4 core. Hence
> I guess fdt_high=0xffffffff has been set to avoid that U-Boot relocates
> the device tree into the DDR area used by the M4. Note that this board
> only has 128MiB of RAM,
> 
> I see that the comments in ti_armv7_common.h is mostly about moving
> stuff into the upper 128MiB, which we don't have. So, with these two
> things in mind, what do you want me to do differently?

So, we want to use bootm_size whenever possible as the way to tell
U-Boot "kernel, ramdisk (if present) and fdt (if present) need to exist
within thus chunk of memory".  So instead of saying
fdt_high/initrd_high=0xffffffff we leave those alone, set bootm_size to
howmuch we can set aside for those three things and let U-Boot sort out
making sure things don't overlap and if they need to be moved.

-- 
Tom
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