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 <[email protected]> Cc: Gerd Hoffmann <[email protected]> Cc: Anthony Perard <[email protected]> Cc: Julien Grall <[email protected]> Cc: Eric Dong <[email protected]> Cc: Ray Ni <[email protected]> Signed-off-by: Min Xu <[email protected]> --- .../Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c index 2d17177df12b..f26d9c93894f 100644 --- a/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c +++ b/UefiCpuPkg/Library/BaseXApicX2ApicLib/BaseXApicX2ApicLib.c @@ -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); } /** -- 2.29.2.windows.2 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#84736): https://edk2.groups.io/g/devel/message/84736 Mute This Topic: https://groups.io/mt/87696607/21656 Group Owner: [email protected] Unsubscribe: https://edk2.groups.io/g/devel/unsub [[email protected]] -=-=-=-=-=-=-=-=-=-=-=-
