Hi,
On 27 June 2018 at 08:06, York Sun york.sun@nxp.com wrote:
+Simon
On 06/27/2018 01:05 AM, Prabhakar Kushwaha wrote:
Hi All,
We are trying to add support of device-tree for PowerPC platforms. As per our analysis following 2 options can be used.
a) CONFIG_OF_SEPARATE b) CONFIG_OF_EMBED
In PowerPC platforms, reset_vector is always expected at the **last** address of flash. U-boot binary has reset_vector at last followed by __bss sections(not present in binary) and must be programmed in such a way that reset_vecrot lie at **last** address of flash.
Hence dtb cannot be appended at last of u-boot binary.
So there looks to be following 2 possible solutions a) Use CONFIG_OF_SEPARATE and append dtb at start of u-boot binary. This require change in flash map because u-boot start address needs to shifted (due to reset_vector requirements). Exiting offset of env and fman ucode also needs shifting. This approach requires modification in almost all existing PowerPC platform to adhere to new **modified** flash map.
b) Use CONFIG_OF_EMBED and embed dtb inside u-boot. This way no change in exiting flash map. But its usage is being discouraged as per doc/README.fdt-control.
Clearly putting dtb at the very end doesn't work, neither last 4KB. I think we either use CONFIG_OF_EMBED (many boards use this way), or try "fdtcontroladdr".
I discourage CONFIG_OF_EMBED - it is a debug feature. I'm not sure if you have other options though.
Can the DT perhaps go before U-Boot in the flash? We would need a way to find it though.
With binman it is possible to put the DT anyway and have a symbol defined to its address. Would that help?
Regards, Simon