> On Fri, Nov 25, 2011 at 9:44 AM, Marek Vasut <marek.va...@gmail.com> wrote: > >> This handler can be activated on multi-processor systems to boot only > >> the master CPU. All slave CPUs are halted by executing the WAIT > >> instruction. This is also useful to reduce the power consumption at > >> boot time. > >> > >> Signed-off-by: Daniel Schwierzeck <daniel.schwierz...@googlemail.com> > >> --- > >> arch/mips/cpu/mips32/start.S | 16 ++++++++++++++++ > >> 1 files changed, 16 insertions(+), 0 deletions(-) > >> > >> diff --git a/arch/mips/cpu/mips32/start.S b/arch/mips/cpu/mips32/start.S > >> index 9c1b2f7..b6cb4be 100644 > >> --- a/arch/mips/cpu/mips32/start.S > >> +++ b/arch/mips/cpu/mips32/start.S > >> @@ -224,6 +224,14 @@ reset: > >> > >> setup_c0_status_reset > >> > >> + /* Set all slave CPUs in sleep mode */ > >> +#ifdef CONFIG_SYS_MPS_SLAVE_CPU_SLEEP > >> + mfc0 k0, CP0_EBASE > >> + and k0, EBASEF_CPUNUM > >> + bne k0, zero, slave_cpu_sleep > >> + nop > >> +#endif > >> + > >> /* Init Timer */ > >> mtc0 zero, CP0_COUNT > >> mtc0 zero, CP0_COMPARE > >> @@ -383,3 +391,11 @@ romReserved: > >> > >> romExcHandle: > >> b romExcHandle > >> + > >> + /* Additional handlers */ > >> +#ifdef CONFIG_SYS_MPS_SLAVE_CPU_SLEEP > >> +slave_cpu_sleep: > >> + wait > >> + b slave_cpu_sleep > >> + nop > >> +#endif > > > > Can't you stall the CPU instead of letting it run in an empty loop? If > > not: > > > > Acked-by: Marek Vasut <marek.va...@gmail.com> > > the CPU is stalled with the wait instruction. The loop is actually paranoia > ;) > > From MIPS32 24KE Processor Core Family Software User's Manual: > > The WAIT instruction forces the core into low power mode. The pipeline > is stalled and when all external requests are > completed, the processor’s main clock is stopped. The processor will > restart when reset (SI_Reset) is signaled, or a > non-masked interrupt is taken (SI_NMI, SI_Int, or EJ_DINT). Note that > the core does not use the code field in this > instruction.
Oh yea, this kind of stuff I remember like I hacked on it yesterday :) _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
