On Fri, Jun 8, 2012 at 11:31 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > On Fri, Jun 8, 2012 at 1:01 AM, Xudong Hao <xudong.hao@xxxxxxxxx> wrote: >> The series of patches enable LTR and OBFF before device is used by driver, and >> introduce a couple of functions to save/restore LTR latency value. >> >> Patch 1/4 introduce new function pci_obff_supported() as pci_ltr_support(). >> >> Patch 2/4 enable LTR(Latency tolerance reporting) before device is used by >> driver. >> >> Patch 3/4 enable OBFF(optimized buffer flush/fill) before device is used by >> driver. >> >> Patch 4/4 introduce a couple of functions pci_save_ltr_value() and >> pci_restore_ltr_value() to save and restore LTR latency value, while device is >> reset. > > We need some justification for these patches. Why do we want them? > Do they improve performance? Reduce power consumption? How have they > been tested? How can we be confident that these features work > correctly on hardware in the field? Should or could the BIOS enable > them itself, based on OEM testing and desire to support these > features? I too am a little nervous about these changes due to Jesse's earlier response (see http://marc.info/?l=linux-pci&m=133372610102933&w=2) where he indicated: "Given how device specific these extensions are, I'd expect you'd need to know about each specific device anyway, which is why I think the control belongs in the driver." Having these features enabled by default may be too aggressive. Not saying it is not correct - something you may be able to inform us about, especially since you are with Intel - just make me nervous without further information. Myron > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
