Remove the irqoff/irqon around MSR-based TSC enumeration,
as it is not necessary.

Also rename: try_msr_calibrate_tsc() to cpu_khz_from_msr(),
as that better describes what the routine does.
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/a6b5c3ecd3b068175d2309599ab28163fc34215e.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

per the Intel 64 and IA-32 Architecture Software Developer's Manual...

Add the reference clock for Intel Atom Processors
Based on the Airmont Microarchitecture.
Reported-by: NStephane Gasparini <stephane.gasparini@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/abc6a0f4b18281410da1a3f26e2819d8e03e144f.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Atom processors use a 19.2 MHz crystal oscillator.

Early processors generate 100 MHz via 19.2 MHz * 26 / 5 = 99.84 MHz.

Later preocessor generate 100 MHz via 19.2 MHz * 125 / 24 = 100 MHz.

Update the Silvermont-based tables accordingly,
matching the Software Developers Manual.

Also, correct a 166 MHz entry that should have been 116 MHz,
and add a missing 80 MHz entry.
Reported-by: NStephane Gasparini <stephane.gasparini@intel.com>
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/5d7561655dfb066ff10801b423405bae4d1cfbe2.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Syntax only, no functional change.
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/8653a2dba21fef122fc7b29eafb750e2004d3976.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Debugging messages are not necessary after all of the
possible hardware failures that never occur.
Instead, this code can simply return 0.

This code also doesn't need to print in the success case.
tsc_init() already prints the TSC frequency,
and apic=debug is available if anybody really is
interested in printing the LAPIC frequency.
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/cf03279a125b95dfa9b8d3d5b4a66de09cd04050.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

try_msr_calibrate_tsc() is currently Intel-specific,
and should not execute on any other vendor's parts.
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1fe23c052826bdcfeb3d45045aa02246078cb5a7.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

This reverts commit:

  e2724e9d ("x86/tsc: Add missing Cherrytrail frequency to the table")

... as it is incomplete, and is replaced by a more complete patch
later in this series.
Signed-off-by: NLen Brown <len.brown@intel.com>
Reviewed-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/2199d0e959f7f71a18827268b5d060f8d3831639.1466138954.git.len.brown@intel.comSigned-off-by: NIngo Molnar <mingo@kernel.org>

Intel Cherrytrail is based on Airmont core so MSR_FSB_FREQ[2:0] = 4
means that the CPU reference clock runs at 80MHz.  Add this missing
frequency to the table.
Signed-off-by: NJeremy Compostella <jeremy.compostella@intel.com>
Link: http://lkml.kernel.org/r/87y47gty89.fsf@intel.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Currently we read the tsc radio: ratio = (MSR_PLATFORM_INFO >> 8) & 0x1f;

Thus we get bit 8-12 of MSR_PLATFORM_INFO, however according to the SDM
(35.5), the ratio bits are bit 8-15.

Ignoring the upper bits can result in an incorrect tsc ratio, which causes the
TSC calibration and the Local APIC timer frequency to be incorrect.

Fix this problem by masking 0xff instead.

[ tglx: Massaged changelog ]

Fixes: 7da7c156 "x86, tsc: Add static (MSR) TSC calibration on Intel Atom SoCs"
Signed-off-by: NChen Yu <yu.c.chen@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: stable@vger.kernel.org
Cc: Bin Gao <bin.gao@intel.com>
Cc: Len Brown <lenb@kernel.org>
Link: http://lkml.kernel.org/r/1462505619-5516-1-git-send-email-yu.c.chen@intel.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

Intel Baytrail is based on Silvermont core so MSR_FSB_FREQ[2:0] == 0 means
that the CPU reference clock runs at 83.3MHz. Add this missing frequency to
the table.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Cc: Bin Gao <bin.gao@linux.intel.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1392810750-18660-2-git-send-email-mika.westerberg@linux.intel.comSigned-off-by: NThomas Gleixner <tglx@linutronix.de>

If we cannot calibrate TSC via MSR based calibration
try_msr_calibrate_tsc() stores zero to fast_calibrate and returns that
to the caller. This value gets then propagated further to clockevents
code resulting division by zero oops like the one below:

 divide error: 0000 [#1] PREEMPT SMP
 Modules linked in:
 CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W    3.13.0+ #47
 task: ffff880075508000 ti: ffff880075506000 task.ti: ffff880075506000
 RIP: 0010:[<ffffffff810aec14>]  [<ffffffff810aec14>] clockevents_config.part.3+0x24/0xa0
 RSP: 0000:ffff880075507e58  EFLAGS: 00010246
 RAX: ffffffffffffffff RBX: ffff880079c0cd80 RCX: 0000000000000000
 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffffffffff
 RBP: ffff880075507e70 R08: 0000000000000001 R09: 00000000000000be
 R10: 00000000000000bd R11: 0000000000000003 R12: 000000000000b008
 R13: 0000000000000008 R14: 000000000000b010 R15: 0000000000000000
 FS:  0000000000000000(0000) GS:ffff880079c00000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
 CR2: ffff880079fff000 CR3: 0000000001c0b000 CR4: 00000000001006f0
 Stack:
  ffff880079c0cd80 000000000000b008 0000000000000008 ffff880075507e88
  ffffffff810aecb0 ffff880079c0cd80 ffff880075507e98 ffffffff81030168
  ffff880075507ed8 ffffffff81d1104f 00000000000000c3 0000000000000000
 Call Trace:
  [<ffffffff810aecb0>] clockevents_config_and_register+0x20/0x30
  [<ffffffff81030168>] setup_APIC_timer+0xc8/0xd0
  [<ffffffff81d1104f>] setup_boot_APIC_clock+0x4cc/0x4d8
  [<ffffffff81d0f5de>] native_smp_prepare_cpus+0x3dd/0x3f0
  [<ffffffff81d02ee9>] kernel_init_freeable+0xc3/0x205
  [<ffffffff8177c910>] ? rest_init+0x90/0x90
  [<ffffffff8177c91e>] kernel_init+0xe/0x120
  [<ffffffff8178deec>] ret_from_fork+0x7c/0xb0
  [<ffffffff8177c910>] ? rest_init+0x90/0x90

Prevent this from happening by:
 1) Modifying try_msr_calibrate_tsc() to return calibration value or zero
    if it fails.
 2) Check this return value in native_calibrate_tsc() and in case of zero
    fallback to use normal non-MSR based calibration.

[mw: Added subject and changelog]
Reported-and-tested-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Bin Gao <bin.gao@linux.intel.com>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1392810750-18660-1-git-send-email-mika.westerberg@linux.intel.comSigned-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

If we aren't going to use the local APIC anyway, we obviously don't
care about its timer frequency.

Link: http://lkml.kernel.org/r/tip-rgm7xmg7k6qnjlw3ynkcjsmh@git.kernel.orgReported-by: NFengguang Wu <fengguang.wu@intel.com>
Cc: Bin Gao <bin.gao@intel.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

On SoCs that have the calibration MSRs available, either there is no
PIT, HPET or PMTIMER to calibrate against, or the PIT/HPET/PMTIMER is
driven from the same clock as the TSC, so calibration is redundant and
just slows down the boot.

TSC rate is caculated by this formula:
<maximum core-clock to bus-clock ratio> * <maximum resolved frequency>
The ratio and the resolved frequency ID can be obtained from MSR.
See Intel 64 and IA-32 System Programming Guid section 16.12 and 30.11.5
for details.
Signed-off-by: NBin Gao <bin.gao@intel.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/n/tip-rgm7xmg7k6qnjlw3ynkcjsmh@git.kernel.org