On Wed, 2013-09-11 at 13:56 +0800, Dongsheng Wang wrote: > From: Wang Dongsheng <dongsheng.w...@freescale.com> > > Each core's AltiVec unit may be placed into a power savings mode > by turning off power to the unit. Core hardware will automatically > power down the AltiVec unit after no AltiVec instructions have > executed in N cycles. The AltiVec power-control is triggered by hardware. > > Signed-off-by: Wang Dongsheng <dongsheng.w...@freescale.com> > --- > *v3: > Assembly code instead of C code. > > *v2: > Remove: > delete setup_idle_hw_governor function. > delete "Fix erratum" for rev1. > > Move: > move setup_* into __setup/restore_cpu_e6500. > > arch/powerpc/kernel/cpu_setup_fsl_booke.S | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/arch/powerpc/kernel/cpu_setup_fsl_booke.S > b/arch/powerpc/kernel/cpu_setup_fsl_booke.S > index bfb18c7..3c03c109 100644 > --- a/arch/powerpc/kernel/cpu_setup_fsl_booke.S > +++ b/arch/powerpc/kernel/cpu_setup_fsl_booke.S > @@ -53,11 +53,30 @@ _GLOBAL(__e500_dcache_setup) > isync > blr > > +/* > + * FIXME - We don't know the AltiVec application scenarios. > + */ > +#define AV_WAIT_IDLE_BIT 50 /* 1ms, TB frequency is 41.66MHZ */ > +_GLOBAL(setup_altivec_idle) > + mfspr r3, SPRN_PWRMGTCR0 > + > + /* Enable Altivec Idle */ > + oris r3, r3, PWRMGTCR0_AV_IDLE_PD_EN@h > + li r4, AV_WAIT_IDLE_BIT > + > + /* Set Automatic AltiVec Idle Count */ > + rlwimi r3, r4, PWRMGTCR0_AV_IDLE_CNT_SHIFT, PWRMGTCR0_AV_IDLE_CNT > + > + mtspr SPRN_PWRMGTCR0, r3 > + > + blr
The FIXME comment is not clear. If you mean that we haven't yet done testing to determine a reasonable default value for AV_WAIT_IDLE_BIT, then just say that. Likewise with the FIXME comment in the pw20 patch -- the uncertainty is due to a lack of investigation, not "because we don't know the current state of the cpu load". While some workloads may want a different value than whatever default we set, that's what the sysfs interface is for. The only thing missing here is benchmarking to determine a good overall default. -Scott _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
