• Thomas Gleixner's avatar
    x86/intel-mid: Delay initialization of APB timer · 6648d1b4
    Thomas Gleixner authored
    MID has no PIC, but depending on the platform it requires the
    abt_timer, which is connected to irq0. The timer is set up at
    late_time_init().
    
    But, looking at the MID code it seems, that there is no reason to do
    so. The only code which might need the timer working is the TSC
    calibration code, but thats a non issue on MID as that is using its
    own empty calibration function. And check_timer() is not invoked
    either because MID has no PIC and therefor no legacy irqs.
    
    So if you look at intel_mid_time_init() then you'll see that in the
    ARAT case the timer setup is skipped already. So until the point where
    x86_init.timers.setup_percpu_clockev() is called for the boot cpu
    nothing really needs a timer on MID.
    
    According to the MID code the apbt horror is only used for moorestown.
    Medfield and later use the local apic timer without the apbt nonsense.
    
    The best thing we can do is to drop moorestown support and get rid of
    that apbt nonsense alltogether.
    
    I don't think anyone deeply cares about it not being supported from
    3.18 on. The number of devices which sport a moorestown should be
    pretty limited and the only relevant use case of those is to act as a
    pocket heater with short battery life time. Its pretty pointless to
    update kernels on pocket heaters except for bragging reasons.
    
    If someone at Intel really thinks that we need to keep moorestown
    alive for other than documentary and sentimental reasons, then we can
    move the apbt setup to x86_init.timers.setup_percpu_clockev(). At that
    point the IOAPIC is setup already, so it should just work.
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Tested-by: default avatarAndy Shevchenko <andriy.shevchenko@linux.intel.com>
    Signed-off-by: default avatarJiang Liu <jiang.liu@linux.intel.com>
    Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    Cc: David Cohen <david.a.cohen@linux.intel.com>
    Cc: Sander Eikelenboom <linux@eikelenboom.it>
    Cc: David Vrabel <david.vrabel@citrix.com>
    Cc: Tony Luck <tony.luck@intel.com>
    Cc: Joerg Roedel <joro@8bytes.org>
    Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    Cc: H. Peter Anvin <hpa@linux.intel.com>
    Cc: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
    Cc: Bjorn Helgaas <bhelgaas@google.com>
    Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
    Cc: Randy Dunlap <rdunlap@infradead.org>
    Cc: Yinghai Lu <yinghai@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dimitri Sivanich <sivanich@sgi.com>
    Cc: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
    Link: http://lkml.kernel.org/r/1428905519-23704-30-git-send-email-jiang.liu@linux.intel.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    6648d1b4
apb_timer.c 10.8 KB