Messages in this thread | | | Date | Tue, 11 Oct 2011 10:18:19 +0800 | Subject | Re: [Question] PM-QoS: PM_QOS_CPU_DMA_LATENCY == interrupt latency? | From | Ming Lei <> |
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Hi,
On Tue, Oct 11, 2011 at 9:49 AM, Shaohua Li <shli@kernel.org> wrote:
> As Alan explained, PM_QOS_CPU_DMA_LATENCY is for dma snooping. For example, > in x86, cpu snoop dma. when cpu is in idle state, cpu need snoop > device dma activity, there > is latency involved for idle state. >
I see, thanks for your clarification.
I also have two further questions about it:
- Except for dma snooping purpose, are there any other cases in which PM_QOS_CPU_DMA_LATENCY is required?
- Are all CPUs required to be involved to dma snoop? Or only one CPU is enough? If one is enough, maybe we can allow other CPUs to reach deeper idle state.
thanks, -- Ming Lei
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