...
CC target/arm/system-pp502x.c
target/arm/system-pp502x.c: In function 'pp_set_cpu_frequency':
target/arm/system-pp502x.c:163: warning: implicit declaration of function 'scale_suspend_core'
...
LD rockbox.elf
/home/user/rockbox/ipodmini/librockbox.a(system-pp502x.o): In function 'pp_set_cpu_frequency':
system-pp502x.c:(.text+0x3b0): undefined reference to 'scale_suspend_core'
collect2: ld returned 1 exit status
make[1]: *** [/home/user/rockbox/ipodmini/apps/rockbox.elf] Error 1
make: *** [build] Error 2