nios2: reserve boot memory for device tree

Make sure to reserve the boot memory for the flattened device tree.
Otherwise it might get overwritten, e.g. when initial_boot_params is
copied, leading to a corrupted FDT and a boot hang/crash:

bootconsole [early0] enabled
Early console on uart16650 initialized at 0xf8001600
OF: fdt: Error -11 processing FDT
Kernel panic - not syncing: setup_cpuinfo: No CPU found in devicetree!

---[ end Kernel panic - not syncing: setup_cpuinfo: No CPU found in devicetree!

Guenter Roeck says:

> I think I found the problem. In unflatten_and_copy_device_tree(), with added
> debug information:
>
> OF: fdt: initial_boot_params=c861e400, dt=c861f000 size=28874 (0x70ca)
>
> ... and then initial_boot_params is copied to dt, which results in corrupted
> fdt since the memory overlaps. Looks like the initial_boot_params memory
> is not reserved and (re-)allocated by early_init_dt_alloc_memory_arch().

Cc: [e-mail]
Reported-by: Guenter Roeck <[e-mail]>
Reference: http://lkml.kernel.org/r/[e-mail]
Tested-by: Guenter Roeck <[e-mail]>
Signed-off-by: Tobias Klauser <[e-mail]>
Acked-by: Ley Foon Tan <[e-mail]>

arch/nios2/kernel/prom.c

···
 	return alloc_bootmem_align(size, align);
 }
 
+int __init early_init_dt_reserve_memory_arch(phys_addr_t base, phys_addr_t size,
+					     bool nomap)
+{
+	reserve_bootmem(base, size, BOOTMEM_DEFAULT);
+	return 0;
+}
+
 void __init early_init_devtree(void *params)
 {
 	__be32 *dtb = (u32 *)__dtb_start;

arch/nios2/kernel/setup.c

···
 	}
 #endif /* CONFIG_BLK_DEV_INITRD */
 
+	early_init_fdt_reserve_self();
+	early_init_fdt_scan_reserved_mem();
+
 	unflatten_and_copy_device_tree();
 
 	setup_cpuinfo();