Hi Prabhakar,
On Thu, Jun 28, 2018 at 6:05 AM, Simon Glass sjg@chromium.org wrote:
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.
Agree.
Can the DT perhaps go before U-Boot in the flash? We would need a way to find it though.
I don't see any issue that DT go after U-Boot in the flash. x86 does this way, and its reset vector is also the last address of flash.
With binman it is possible to put the DT anyway and have a symbol defined to its address. Would that help?
Regards, Bin