Messages in this thread | | | Date | Fri, 18 Apr 2014 15:18:23 +0800 | From | Feng Tang <> | Subject | Re: [PATCH v2] x86: hpet: Don't default CONFIG_HPET_TIMER to be y for X86_64 |
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Hi All,
On Wed, Apr 16, 2014 at 08:51:48AM +0200, Ingo Molnar wrote: > > * Feng Tang <feng.tang@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
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