kernel/linux.git/arch/powerpc/include/asm/time.h, branch v6.19.11

powerpc/time: Expose boot_tb via accessor

2025-09-22T09:18:56+00:00

- Define accessor function get_boot_tb() to safely return boot_tb value, this is only needed when running in SPLPAR environments, so the accessor is built conditionally under CONFIG_PPC_SPLPAR. - Tag boot_tb as __ro_after_init since it is written once at initialized and never updated afterwards. Signed-off-by: Aboorva Devarajan Tested-by: Tejas Manhas Tested-by: Venkat Rao Bagalkote Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/20250915102947.26681-2-atrajeev@linux.ibm.com

powerpc/time: Define div128_by_32() static and __init

2025-02-24T06:56:21+00:00

div128_by_32() used to be called from outside time.c in the old days but since v2.6.15 it hasn't been used outside time.c $ git grep div128_by_32 v2.6.14 v2.6.14:arch/ppc64/kernel/iSeries_setup.c: div128_by_32(1024 * 1024, 0, tb_ticks_per_sec, &divres); v2.6.14:arch/ppc64/kernel/pmac_time.c: div128_by_32( 1024*1024, 0, tb_ticks_per_sec, &divres ); v2.6.14:arch/ppc64/kernel/time.c: div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres ); v2.6.14:arch/ppc64/kernel/time.c: div128_by_32(1024*1024, 0, tb_ticks_per_sec, &divres); v2.6.14:arch/ppc64/kernel/time.c: div128_by_32(1000000000, 0, tb_ticks_per_sec, &res); v2.6.14:arch/ppc64/kernel/time.c: div128_by_32( 1024*1024, 0, new_tb_ticks_per_sec, &divres ); v2.6.14:arch/ppc64/kernel/time.c:void div128_by_32( unsigned long dividend_high, unsigned long dividend_low, v2.6.14:include/asm-ppc64/time.h:void div128_by_32( unsigned long dividend_high, unsigned long dividend_low, $ git grep div128_by_32 v2.6.15 v2.6.15:arch/powerpc/kernel/time.c: div128_by_32( XSEC_PER_SEC, 0, tb_ticks_per_sec, &divres ); v2.6.15:arch/powerpc/kernel/time.c: div128_by_32(1024*1024, 0, tb_ticks_per_sec, &res); v2.6.15:arch/powerpc/kernel/time.c: div128_by_32(1000000000, 0, tb_ticks_per_sec, &res); v2.6.15:arch/powerpc/kernel/time.c: div128_by_32(1024*1024, 0, new_tb_ticks_per_sec, &divres); v2.6.15:arch/powerpc/kernel/time.c:void div128_by_32(u64 dividend_high, u64 dividend_low, v2.6.15:include/asm-powerpc/time.h:extern void div128_by_32(u64 dividend_high, u64 dividend_low, Move it above its only caller which is time_init() and define it static and __init. Signed-off-by: Christophe Leroy Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/50810349bf1eee378fbeab72a36e4b6553a60c3d.1738749246.git.christophe.leroy@csgroup.eu

powerpc/32: Replace mulhdu() by mul_u64_u64_shr()

2024-12-10T02:45:30+00:00

Using mul_u64_u64_shr() provides similar calculation as mulhdu() assembly function, but enables inlining by the compiler. The home-made assembly function had special handling for when one of the arguments is not a fully populated u64 but time functions use it to multiply timebase by a calculated scale which is constructed to have most significant bit set. On mpc8xx sched_clock() runs 3% faster. On mpc83xx it is 2%. As you can see below, sched_clock() is not much bigger than before: c000cf68 : c000cf68: 7d 2d 42 a6 mftbu r9 c000cf6c: 7d 0c 42 a6 mftb r8 c000cf70: 7d 4d 42 a6 mftbu r10 c000cf74: 7c 09 50 40 cmplw r9,r10 c000cf78: 40 82 ff f0 bne c000cf68 c000cf7c: 3d 40 c1 37 lis r10,-16073 c000cf80: 38 8a b3 30 addi r4,r10,-19664 c000cf84: 80 ea b3 30 lwz r7,-19664(r10) c000cf88: 80 64 00 14 lwz r3,20(r4) c000cf8c: 39 40 00 00 li r10,0 c000cf90: 80 a4 00 04 lwz r5,4(r4) c000cf94: 80 c4 00 10 lwz r6,16(r4) c000cf98: 7c 63 40 10 subfc r3,r3,r8 c000cf9c: 80 84 00 08 lwz r4,8(r4) c000cfa0: 7d 06 49 10 subfe r8,r6,r9 c000cfa4: 7c c7 19 d6 mullw r6,r7,r3 c000cfa8: 7d 25 18 16 mulhwu r9,r5,r3 c000cfac: 7c 08 29 d6 mullw r0,r8,r5 c000cfb0: 7c 67 18 16 mulhwu r3,r7,r3 c000cfb4: 7d 29 30 14 addc r9,r9,r6 c000cfb8: 7c a8 28 16 mulhwu r5,r8,r5 c000cfbc: 7c ca 51 14 adde r6,r10,r10 c000cfc0: 7d 67 41 d6 mullw r11,r7,r8 c000cfc4: 7d 29 00 14 addc r9,r9,r0 c000cfc8: 7c c6 01 94 addze r6,r6 c000cfcc: 7c 63 28 14 addc r3,r3,r5 c000cfd0: 7d 4a 51 14 adde r10,r10,r10 c000cfd4: 7c e7 40 16 mulhwu r7,r7,r8 c000cfd8: 7c 63 58 14 addc r3,r3,r11 c000cfdc: 7d 4a 01 94 addze r10,r10 c000cfe0: 7c 63 30 14 addc r3,r3,r6 c000cfe4: 7d 4a 39 14 adde r10,r10,r7 c000cfe8: 35 24 ff e0 addic. r9,r4,-32 c000cfec: 41 80 00 10 blt c000cffc c000cff0: 7c 63 48 30 slw r3,r3,r9 c000cff4: 38 80 00 00 li r4,0 c000cff8: 4e 80 00 20 blr c000cffc: 21 04 00 1f subfic r8,r4,31 c000d000: 54 69 f8 7e srwi r9,r3,1 c000d004: 7d 4a 20 30 slw r10,r10,r4 c000d008: 7d 29 44 30 srw r9,r9,r8 c000d00c: 7c 64 20 30 slw r4,r3,r4 c000d010: 7d 23 53 78 or r3,r9,r10 c000d014: 4e 80 00 20 blr Before this change: c000d0bc : c000d0bc: 94 21 ff f0 stwu r1,-16(r1) c000d0c0: 7c 08 02 a6 mflr r0 c000d0c4: 90 01 00 14 stw r0,20(r1) c000d0c8: 93 e1 00 0c stw r31,12(r1) c000d0cc: 7d 2d 42 a6 mftbu r9 c000d0d0: 7d 0c 42 a6 mftb r8 c000d0d4: 7d 4d 42 a6 mftbu r10 c000d0d8: 7c 09 50 40 cmplw r9,r10 c000d0dc: 40 82 ff f0 bne c000d0cc c000d0e0: 3f e0 c1 37 lis r31,-16073 c000d0e4: 3b ff b3 30 addi r31,r31,-19664 c000d0e8: 80 9f 00 14 lwz r4,20(r31) c000d0ec: 80 7f 00 10 lwz r3,16(r31) c000d0f0: 7c 84 40 10 subfc r4,r4,r8 c000d0f4: 80 bf 00 00 lwz r5,0(r31) c000d0f8: 80 df 00 04 lwz r6,4(r31) c000d0fc: 7c 63 49 10 subfe r3,r3,r9 c000d100: 48 00 37 85 bl c0010884 c000d104: 81 3f 00 08 lwz r9,8(r31) c000d108: 35 49 ff e0 addic. r10,r9,-32 c000d10c: 41 80 00 20 blt c000d12c c000d110: 80 01 00 14 lwz r0,20(r1) c000d114: 7c 83 50 30 slw r3,r4,r10 c000d118: 83 e1 00 0c lwz r31,12(r1) c000d11c: 38 80 00 00 li r4,0 c000d120: 7c 08 03 a6 mtlr r0 c000d124: 38 21 00 10 addi r1,r1,16 c000d128: 4e 80 00 20 blr c000d12c: 80 01 00 14 lwz r0,20(r1) c000d130: 54 8a f8 7e srwi r10,r4,1 c000d134: 21 09 00 1f subfic r8,r9,31 c000d138: 83 e1 00 0c lwz r31,12(r1) c000d13c: 7c 63 48 30 slw r3,r3,r9 c000d140: 7d 4a 44 30 srw r10,r10,r8 c000d144: 7c 84 48 30 slw r4,r4,r9 c000d148: 7d 43 1b 78 or r3,r10,r3 c000d14c: 7c 08 03 a6 mtlr r0 c000d150: 38 21 00 10 addi r1,r1,16 c000d154: 4e 80 00 20 blr c0010884 : c0010884: 2c 06 00 00 cmpwi r6,0 c0010888: 2c 83 00 00 cmpwi cr1,r3,0 c001088c: 7c 8a 23 78 mr r10,r4 c0010890: 7c 84 28 16 mulhwu r4,r4,r5 c0010894: 41 82 00 14 beq c00108a8 c0010898: 7c 0a 30 16 mulhwu r0,r10,r6 c001089c: 7c ea 29 d6 mullw r7,r10,r5 c00108a0: 7c e0 38 14 addc r7,r0,r7 c00108a4: 7c 84 01 94 addze r4,r4 c00108a8: 4d 86 00 20 beqlr cr1 c00108ac: 7d 23 29 d6 mullw r9,r3,r5 c00108b0: 7d 43 28 16 mulhwu r10,r3,r5 c00108b4: 41 82 00 18 beq c00108cc c00108b8: 7c 03 31 d6 mullw r0,r3,r6 c00108bc: 7d 03 30 16 mulhwu r8,r3,r6 c00108c0: 7c e0 38 14 addc r7,r0,r7 c00108c4: 7c 84 41 14 adde r4,r4,r8 c00108c8: 7d 4a 01 94 addze r10,r10 c00108cc: 7c 84 48 14 addc r4,r4,r9 c00108d0: 7c 6a 01 94 addze r3,r10 c00108d4: 4e 80 00 20 blr Signed-off-by: Christophe Leroy Signed-off-by: Madhavan Srinivasan Link: https://patch.msgid.link/f29e473c193c87bdbd36b209dfdee99d2f0c60dc.1733566130.git.christophe.leroy@csgroup.eu

powerpc: Remove core support for 40x

2024-06-28T12:28:47+00:00

Now that 40x platforms have gone, remove support for 40x in the core of powerpc arch. Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://msgid.link/20240628121201.130802-4-mpe@ellerman.id.au

powerpc/pseries: Move dtl scanning and steal time accounting to pseries platform

2022-09-05T04:14:27+00:00

dtl is the PAPR Dispatch Trace Log, which is entirely a pseries feature. The pseries platform alrady has a file dealing with the dtl, so move scanning for stolen time accounting there from kernel/time.c. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20220902085316.2071519-5-npiggin@gmail.com

powerpc/time: Fix sparse warnings

2022-05-04T09:37:42+00:00

We found these warnings in arch/powerpc/kernel/time.c as follows: warning: symbol 'decrementer_max' was not declared. Should it be static? warning: symbol 'rtc_lock' was not declared. Should it be static? warning: symbol 'dtl_consumer' was not declared. Should it be static? Declare 'decrementer_max' in powerpc asm/time.h. Include linux/mc146818rtc.h in powerpc kernel/time.c where 'rtc_lock' is declared. And remove duplicated declaration of 'rtc_lock' in powerpc platforms/chrp/time.c because it has included linux/mc146818rtc.h. Move 'dtl_consumer' definition after "include " because it is declared there. Reported-by: Hulk Robot Signed-off-by: He Ying Reviewed-by: Christophe Leroy Reviewed-by: Alexandre Belloni Signed-off-by: Christophe Leroy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210324090939.143477-1-heying24@huawei.com

powerpc/time: add API for KVM to re-arm the host timer/decrementer

2021-11-24T10:08:57+00:00

Rather than have KVM look up the host timer and fiddle with the irq-work internal details, have the powerpc/time.c code provide a function for KVM to re-arm the Linux timer code when exiting a guest. This is implementation has an improvement over existing code of marking a decrementer interrupt as soft-pending if a timer has expired, rather than setting DEC to a -ve value, which tended to cause host timers to take two interrupts (first hdec to exit the guest, then the immediate dec). Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211123095231.1036501-8-npiggin@gmail.com

KVM: PPC: Book3S HV P9: Use large decrementer for HDEC

2021-11-24T10:08:57+00:00

On processors that don't suppress the HDEC exceptions when LPCR[HDICE]=0, this could help reduce needless guest exits due to leftover exceptions on entering the guest. Signed-off-by: Nicholas Piggin Reviewed-by: Alexey Kardashevskiy Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211123095231.1036501-6-npiggin@gmail.com

KVM: PPC: Book3S HV P9: Use host timer accounting to avoid decrementer read

2021-11-24T10:08:56+00:00

There is no need to save away the host DEC value, as it is derived from the host timer subsystem which maintains the next timer time, so it can be restored from there. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20211123095231.1036501-5-npiggin@gmail.com

KVM: PPC: Book3S HV P9: Reduce irq_work vs guest decrementer races

2021-06-10T12:12:13+00:00

irq_work's use of the DEC SPR is racy with guest<->host switch and guest entry which flips the DEC interrupt to guest, which could lose a host work interrupt. This patch closes one race, and attempts to comment another class of races. Signed-off-by: Nicholas Piggin Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20210528090752.3542186-11-npiggin@gmail.com