hi, list:
I've read Documentation/powerpc/booting-without-of.txt & some documents about fdt/dtb, as booting-without-of.txt said, the bootloader like u-boot should passing fdt as $r3, the kernel entry (physical) address as $r4;
r3 : physical pointer to the device-tree block (defined in chapter II) in RAM
r4 : physical pointer to the kernel itself. This is used by the assembly code to properly disable the MMU in case you are entering the kernel with MMU enabled and a non-1:1 mapping.
r5 : NULL (as to differentiate with method a)
I see fdt is something like:
struct fdt_header { uint32_t magic; /* magic word FDT_MAGIC */ uint32_t totalsize; /* total size of DT block */ uint32_t off_dt_struct; /* offset to structure */ uint32_t off_dt_strings; /* offset to strings */ uint32_t off_mem_rsvmap; /* offset to memory reserve map */ uint32_t version; /* format version */ uint32_t last_comp_version; /* last compatible version */
/* version 2 fields below */ uint32_t boot_cpuid_phys; /* Which physical CPU id we're booting on */ /* version 3 fields below */ uint32_t size_dt_strings; /* size of the strings block */
/* version 17 fields below */ uint32_t size_dt_struct; /* size of the structure block */ };
My question is how does the kernel cmd line being passed? I know it's possible for u-boot to patching the target uImage (assume we're using kernel image cuImage.bamboo)'s dtb by overwrite the dtb ``chosen'' section, but I didn't find any code in u-boot trying to do this.
Even more, after the kernel is bootstraping, (assume we're using a bamboo board), we'll run into:
static bd_t bd;
... void platform_init(unsigned long r3, unsigned long r4, unsigned long r5, unsigned long r6, unsigned long r7) { CUBOOT_INIT(); bamboo_init(&bd.bi_enetaddr, &bd.bi_enet1addr); }
...
void bamboo_init(void *mac0, void *mac1) { platform_ops.fixups = bamboo_fixups; platform_ops.exit = ibm44x_dbcr_reset; bamboo_mac0 = mac0; bamboo_mac1 = mac1; fdt_init(_dtb_start); serial_console_init(); } ...
this code will assume $r3 is passed as a ``bd_t'' structure, but $r3 passed in I think it's the dtb address (not bd_t), and bamboo_init will set the NIC wrong MAC addresses. I'm quite sure I misunderstand something between u-boot & linux kernel, could some help me to figure it out? Thanks in advance!
Best Regards, Wang Baojun