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UefiCpuPkg: Setting initial-count register as the last step 

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3711

Per SDM, changing the mode of APIC timer (from one-shot to periodic or
vice versa) by writing to the timer LVT entry does not start the timer.
To start the timer, it is necessary to write to the initial-count
register.

If initial-count is wrote before mode change, it's possible that timer
expired before the mode change. Thus failing the periodic mode.

Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
Signed-off-by: Min Xu <min.m.xu@intel.com>
This commit is contained in:
Min Xu 2021-11-29 10:46:40 +08:00 committed by mergify[bot]
parent c2e7be4055
commit 299c44cd4f
1 changed files with 5 additions and 5 deletions
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10
UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c
View File

@ -967,11 +967,6 @@ InitializeApicTimer (
//
InitializeLocalApicSoftwareEnable (TRUE);
//
// Program init-count register.
//
WriteLocalApicReg (XAPIC_TIMER_INIT_COUNT_OFFSET, InitCount);
if (DivideValue != 0) {
ASSERT (DivideValue <= 128);
ASSERT (DivideValue == GetPowerOfTwo32 ((UINT32)DivideValue));
@ -996,6 +991,11 @@ InitializeApicTimer (
LvtTimer.Bits.Mask = 0;
LvtTimer.Bits.Vector = Vector;
WriteLocalApicReg (XAPIC_LVT_TIMER_OFFSET, LvtTimer.Uint32);
//
// Program init-count register.
//
WriteLocalApicReg (XAPIC_TIMER_INIT_COUNT_OFFSET, InitCount);
}
/**