On Thu, Jun 3, 2010 at 4:52 PM, Kevin Hilman <khilman@xxxxxxxxxxxxxxxxxxx> wrote: > Mike Chan <mike@xxxxxxxxxxx> writes: > >> On Fri, May 21, 2010 at 9:47 AM, Kevin Hilman >> <khilman@xxxxxxxxxxxxxxxxxxx> wrote: >>> Mike Chan <mike@xxxxxxxxxxx> writes: >>> >>>> I'm not sure if this has been discussed, yet but since it seems that >>>> the resource framework will not be making it upstream, I am curious >>>> what are the replacements under consideration. I am starting to see >>>> similar issues on other platforms (msm / tegra) so more generic >>>> (non-omap) solution might be something to consider. >>> >>> Hi Mike, >>> >>> Which parts of the SRF do you currently use and find useful? It would >>> be helpful for us to to understand the parts you see as useful and >>> potentially helpful to generalize. >>> >> >> Off the top of my head, for Droid specifically, OPP values are useful, >> although in theory if you changed OPP requests to cpu throughput that >> might give the equivalent functionality. >> >> Memory bus speeds / bandwidth, although its tied to CPU, which >> ultimately ends up in a cpu speed bump. >> >> Although most of the usage I've seen are just hacks, ie: the driver >> knows it needs 550mhz from the cpu so it will request some bogus >> value. >> >> >>> As you know, the current implementation has a several layers >>> and attempts to manage several things: OPPs, latencies etc. >>> >>> Our current plans are essentially to break up the "one framework to >>> rule them all" philosophy and design of SRF and manage the various >>> pieces by exending other layers such as the new OPP layer and voltage >>> layers. Latencies are being managed by the omap_device layer and we >>> will hopefully have some discussions with the broader linux-pm >>> community about generalizing that more into the generic driver model >>> over this year. >>> >> >> Bus speed is a common resource I see for omap / msm / tegra. Clocks >> for devices also. >> >> ie: If I'm doing heavy mem operation and need max memory bus, I might >> need to request higher performance. (which might mean 600mhz on >> omap34030, on msm it might mean AXI clock running at 128mhz, and >> something else on tegra). >> >> Or if I'm doing graphics, I may need to up the gfx clock rate, or >> swich which pll its sourcing etc.. etc.. >> >> It doesn't look like pm qos has bus support, or even clock support, >> and this gets tricky if you want something semi-general. > > What we're hoping to work towards (and has come up in the suspend > blocker related discussions) is moving towards a way to track > per-device (or per-subsystem) constraints like latency and throughput > in real world terms (usecs, bytes/sec, etc.) that would be general > way. > > These constraints would then be visible to the bus- or > platform-specific code that could make intelligent decisions with them > (i.e whether or not to raise/lower OPP or bus speed, or whether or not > to power down a powerdomain etc.) > I saw a little bit on lkml / linux-pm but I may have missed some of the threads. I'm assuming these changes you're talking about are going to be an extension to pm qos. > That's the pie-in-the-sky future I'm hoping for, and I hope to get > some broader discussions around this going at some conferences this > later year (LinuxCon in Aug, Plumbers in Nov, etc.) We had some early > discussions in this direction at ELC already, but it needs some more > thought and discussion. > I think for OMAP we will be ok with the existing / incremental changes to the SRF. Your overview of the pie-in-the-sky might be promising but I'm not sure how timely things will happen. I suppose I should track linux-pm more closely, I'd rather not do a bunch of throw-away work on pm qos. -- Mike > Kevin > -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
