On Thu, 19 Nov 2009 11:20:50 +0100 "Stephane GONAUER" <stephane.gonauer@xxxxxxxxxxxx> wrote: > I am a embedded system designer and currently working on the > preliminary design of a PCIepress expansion board to be used on x86 > motherboard. > > My board is to be an x1 PCie board. Thus according to the PCIe > electromechanical specifications, the board may consume 10Watts by > default, and 25Watts after correct dialog is established with upper > bridges and the root complex. (which after acknowledging the request > should send a Slot_Power_Limit message to the board to allow for > higher power consumption). > > The board is based on a PEX8311 PCIe to local bus chip from PLX tech. > This component is able to present its request for more power using > the power budgeting capability as defined by the PCIe standard. > > However this doesn’t seems to have effect on the system (running > latest ubuntu with 2.6.31 kernel) and from my understanding of the > kernel sources this is not supported. Is that correct ? > > Are there ways that I’m not aware to request for more power in the > existing source base ? Not in PCIe that I'm aware of, aside from the existing ASPM support, but that's a bit different. > I’ve been reading the PCIE-port driver source to try to find a way to > achieve my goal. My understanding is that this driver is very generic > and as such shouldn’t be able to support power budgeting. I believe > adding Power budgeting to it would require to match more closely the > motherboard hardware. Am I correct ? Yeah, we'd need to get power budget info from the firmware or platform somehow, which means we'd have to add a platform specific portion to the PCIe port driver, or at the very least some basic power initialization routines that could be called from platform specific code. > Perhaps you have better ideas on the subject than me. > > I’d be very glad if I could get some comments on this issue. I hope I > haven’t been writing to the wrong people. Given how long it's taken me to reply, maybe you have an implementation already. :) We'd definitely be interested in adding such a feature if your platform supports it and has need of it. -- Jesse Barnes, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
