Hi All, On Wed, Apr 16, 2014 at 08:51:48AM +0200, Ingo Molnar wrote: > > * Feng Tang <feng.t...@intel.com> wrote: > > > > > > > > > > > > > > > > > I thought about this before, HPET doesn't have PCI ID like > > > > > > > > > stuff, > > > > > > > > > > > > > > > > HPET does have the PCI vendor ID in the first register. > > > > > > > > > > > > > > > > > only thing I can think of to identify them may be the CPU > > > > > > > > > family/ID. > > > > > > > > > > > > > > > > The HPET is implemented by some actual chip, and that chip also > > > > > > > > has lots > > > > > > > > of PCI devices. (In the case of a SoC, the CPU ID would work, > > > > > > > > too). > > > > > > > > > > > > > > Correct. See arch/x86/kernel/hpet.c, which has a large number of > > > > > > > HPET > > > > > > > quirks keyed off chipset PCI IDs: > > > > > > > > > > > > > > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, > > > > > > > PCI_DEVICE_ID_INTEL_ESB2_0, > > > > > > > ich_force_enable_hpet); > > > > > > > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, > > > > > > > PCI_DEVICE_ID_INTEL_ICH6_0, > > > > > > > ich_force_enable_hpet); > > > > > > > DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, > > > > > > > PCI_DEVICE_ID_INTEL_ICH6_1, > > > > > > > ich_force_enable_hpet); > > > > > > > [...] > > > > > > > > > > > > I just gave it another thought, that the HPET on our platform > > > > > > currently do have some problem to be used as > > > > > > clocksource/clockevent, > > > > > > but it may get fixed in future version (by Silicon or BIOS). > > > > > > > > > > > > If I add quirk to block it now, I may revert this code in future > > > > > > when it get fixed, same problem applis for the future generation of > > > > > > platform. > > > > > > > > > > If the hardware or BIOS gets fixed then that will be visible in the > > > > > revision level of the hardware, right? > > > > > > > > AFAIK, if it is fixed in a new silicon version, we should be able to > > > > detect it by the "stepping", but the PCI DEV ID is not likely to > > > > change. > > > > > > > > If it is fixed by BIOS or PUNIT FW, then we may go through the > > > > DMI info to check the BIOS version, One problem is there is some > > > > Baytrail tablet platforms that doesn't provide DMI info as its > > > > FW is not UEFI/Legacy BIOS compatible version. > > > > > > So just turn it off for the current hardware, via PCI ID. When you > > > get a fix, you can turn it back on again by refining the quirk > > > check, for that specific hardware. > > > > got it, thanks! > > Btw., note that such narrow quirk refinings are pretty uncontroversial > and have a pretty fast path upstream, once you have the initial quirk > in there.
During implementing, I found the arch/x86/kerne/quirks.c doesn't fit well as the DECLARE_PCI_FIXUP_HEADER/EARLY/FINAL() way of quirk happens inside the pci subsystem init phase, while the hpet_enable() will be called before that. Then by searching the arch/x86/, the early-quirks.c can be used to add such a quirk as the early quirks are checked earlier than hpet_enable() I'll post a RFC patch soon. Thanks, Feng -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
