From: Thomas Gleixner <tglx@linutronix.de>
To: Bjorn Helgaas <helgaas@kernel.org>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org, linux-pci@vger.kernel.org,
linux-kernel@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
Feng Tang <feng.tang@intel.com>,
Kai-Heng Feng <kai.heng.feng@canonical.com>
Subject: Re: [PATCH] x86/PCI: Convert force_disable_hpet() to standard quirk
Date: Wed, 25 Nov 2020 13:46:23 +0100 [thread overview]
Message-ID: <87v9dtk3j4.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <20201119181904.149129-1-helgaas@kernel.org>
On Thu, Nov 19 2020 at 12:19, Bjorn Helgaas wrote:
> 62187910b0fc ("x86/intel: Add quirk to disable HPET for the Baytrail
> platform") implemented force_disable_hpet() as a special early quirk.
> These run before the PCI core is initialized and depend on the
> x86/pci/early.c accessors that use I/O ports 0xcf8 and 0xcfc.
>
> But force_disable_hpet() doesn't need to be one of these special early
> quirks. It merely sets "boot_hpet_disable", which is tested by
> is_hpet_capable(), which is only used by hpet_enable() and hpet_disable().
> hpet_enable() is an fs_initcall(), so it runs after the PCI core is
> initialized.
hpet_enable() is not an fs_initcall(). hpet_late_init() is and that
invokes hpet_enable() only for the case that ACPI did not advertise it
and the force_hpet quirk provided a base address.
But hpet_enable() is also invoked via:
start_kernel()
late_time_init()
x86_late_time_init()
hpet_time_init()
which is way before the PCI core is available and we really don't want
to set it up there if it's known to be broken :)
Now the more interesting question is why this needs to be a PCI quirk in
the first place. Can't we just disable the HPET based on family/model
quirks?
e0748539e3d5 ("x86/intel: Disable HPET on Intel Ice Lake platforms")
f8edbde885bb ("x86/intel: Disable HPET on Intel Coffee Lake H platforms")
fc5db58539b4 ("x86/quirks: Disable HPET on Intel Coffe Lake platforms")
62187910b0fc ("x86/intel: Add quirk to disable HPET for the Baytrail platform")
I might be missing something here, but in general on anything modern
HPET is mostly useless.
Thanks,
tglx
next prev parent reply other threads:[~2020-11-25 12:46 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-19 18:19 [PATCH] x86/PCI: Convert force_disable_hpet() to standard quirk Bjorn Helgaas
2020-11-24 23:27 ` Bjorn Helgaas
2020-11-25 12:46 ` Thomas Gleixner [this message]
2020-11-25 19:13 ` Bjorn Helgaas
2020-11-26 0:50 ` Thomas Gleixner
2020-11-26 1:24 ` Feng Tang
2020-11-26 23:27 ` Thomas Gleixner
2020-11-27 6:11 ` Feng Tang
2020-11-30 19:21 ` Thomas Gleixner
2020-12-01 8:34 ` Feng Tang
2020-12-02 7:28 ` Zhang Rui
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