Date: Mon, 17 Feb 2025 16:37:00 GMT From: Andrew Turner <andrew@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 43b3e755d075 - main - arm64: use FEAT_WFxT for DELAY() when available Message-ID: <202502171637.51HGb0kT082898@gitrepo.freebsd.org>
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The branch main has been updated by andrew: URL: https://cgit.FreeBSD.org/src/commit/?id=43b3e755d07576da8a169a2d000d0f4b4ce33f19 commit 43b3e755d07576da8a169a2d000d0f4b4ce33f19 Author: Harry Moulton <harry.moulton@arm.com> AuthorDate: 2025-02-17 16:01:48 +0000 Commit: Andrew Turner <andrew@FreeBSD.org> CommitDate: 2025-02-17 16:07:36 +0000 arm64: use FEAT_WFxT for DELAY() when available Use a wfet, rather than a busy wait, in DELAY() when the FEAT_WFxT extension is available. Reviewed by: andrew Sponsored by: Arm Ltd Differential Revision: https://reviews.freebsd.org/D48580 Signed-off-by: Harry Moulton <harry.moulton@arm.com> --- sys/arm/arm/generic_timer.c | 86 +++++++++++++++++++++++++++++++++++---------- 1 file changed, 67 insertions(+), 19 deletions(-) diff --git a/sys/arm/arm/generic_timer.c b/sys/arm/arm/generic_timer.c index 775290960ebd..685398117396 100644 --- a/sys/arm/arm/generic_timer.c +++ b/sys/arm/arm/generic_timer.c @@ -60,6 +60,8 @@ #if defined(__aarch64__) #include <machine/undefined.h> +#include <machine/cpufunc.h> +#include <machine/cpu_feat.h> #endif #ifdef FDT @@ -94,6 +96,10 @@ #define GT_CNTKCTL_PL0VCTEN (1 << 1) /* PL0 CNTVCT and CNTFRQ access */ #define GT_CNTKCTL_PL0PCTEN (1 << 0) /* PL0 CNTPCT and CNTFRQ access */ +#if defined(__aarch64__) +static bool __read_mostly enable_wfxt = false; +#endif + struct arm_tmr_softc; struct arm_tmr_irq { @@ -805,12 +811,10 @@ EARLY_DRIVER_MODULE(timer, acpi, arm_tmr_acpi_driver, 0, 0, BUS_PASS_TIMER + BUS_PASS_ORDER_MIDDLE); #endif -static void -arm_tmr_do_delay(int usec, void *arg) +static int64_t +arm_tmr_get_counts(int usec) { - struct arm_tmr_softc *sc = arg; - int32_t counts, counts_per_usec; - uint32_t first, last; + int64_t counts, counts_per_usec; /* Get the number of times to count */ counts_per_usec = ((arm_tmr_timecount.tc_frequency / 1000000) + 1); @@ -826,12 +830,30 @@ arm_tmr_do_delay(int usec, void *arg) else counts = usec * counts_per_usec; + return counts; +} + +static void +arm_tmr_do_delay(int usec, void *arg) +{ + struct arm_tmr_softc *sc = arg; + int64_t counts; + uint64_t first; +#if defined(__aarch64__) + int64_t end; +#endif + + counts = arm_tmr_get_counts(usec); first = sc->get_cntxct(sc->physical_sys); +#if defined(__aarch64__) + end = first + counts; +#endif - while (counts > 0) { - last = sc->get_cntxct(sc->physical_sys); - counts -= (int32_t)(last - first); - first = last; + while ((sc->get_cntxct(sc->physical_sys) - first) < counts) { +#if defined(__aarch64__) + if (enable_wfxt) + wfet(end); +#endif } } @@ -843,21 +865,47 @@ DELAY(int usec) TSENTER(); /* - * Check the timers are setup, if not just - * use a for loop for the meantime - */ - if (arm_tmr_sc == NULL) { + * We have two options for a delay: using the timer, or using the wfet + * instruction. However, both of these are dependent on timers being + * setup, and if they're not just use a loop for the meantime. + */ + if (arm_tmr_sc != NULL) { + arm_tmr_do_delay(usec, arm_tmr_sc); + } else { for (; usec > 0; usec--) for (counts = 200; counts > 0; counts--) - /* - * Prevent the compiler from optimizing - * out the loop - */ + /* Prevent the compiler from optimizing out the loop */ cpufunc_nullop(); - } else - arm_tmr_do_delay(usec, arm_tmr_sc); + } TSEXIT(); } + +static bool +wfxt_check(const struct cpu_feat *feat __unused, u_int midr __unused) +{ + uint64_t id_aa64isar2; + + if (!get_kernel_reg(ID_AA64ISAR2_EL1, &id_aa64isar2)) + return (false); + return (ID_AA64ISAR2_WFxT_VAL(id_aa64isar2) != ID_AA64ISAR2_WFxT_NONE); +} + +static void +wfxt_enable(const struct cpu_feat *feat __unused, + cpu_feat_errata errata_status __unused, u_int *errata_list __unused, + u_int errata_count __unused) +{ + /* will be called if wfxt_check returns true */ + enable_wfxt = true; +} + +static struct cpu_feat feat_wfxt = { + .feat_name = "FEAT_WFXT", + .feat_check = wfxt_check, + .feat_enable = wfxt_enable, + .feat_flags = CPU_FEAT_AFTER_DEV | CPU_FEAT_SYSTEM, +}; +DATA_SET(cpu_feat_set, feat_wfxt); #endif static uint32_t
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