Messages in this thread | | | Date | Mon, 28 Jan 2008 15:14:50 -0800 | From | "Kok, Auke" <> | Subject | Re: [PATCH]PCIE ASPM support - takes 3 |
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Pavel Machek wrote: > Hi! > >> v3->v2, fixed the issues Matthew Wilcox raised. >> >> PCI Express ASPM defines a protocol for PCI Express components in the D0 >> state to reduce Link power by placing their Links into a low power state >> and instructing the other end of the Link to do likewise. This >> capability allows hardware-autonomous, dynamic Link power reduction >> beyond what is achievable by software-only controlled power management. >> However, The device should be configured by software appropriately. >> Enabling ASPM will save power, but will introduce device latency. > > How big is the latency? 1msec? 10msec? 100usec?
the latency is different for each device but the timing is negotiated and the pci-e spec lists possible timings that can be used. The maximum is (I think...) 64usec but can be as low as 1 or 2 usec.
Auke
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