From 3149cc9df6bd219b121a504e0e01c5f76532d2f4 Mon Sep 17 00:00:00 2001 From: Rui Paulo Date: Fri, 24 Oct 2014 18:39:15 +0000 Subject: [PATCH] HPET: create /dev/hpetN as a way to access HPET from userland. In some cases, TSC is broken and special applications might benefit from memory mapping HPET and reading the registers to count time. Most often the main HPET counter is 32-bit only[1], so this only gives the application a 300 second window based on the default HPET interval. Other applications, such as Intel's DPDK, expect /dev/hpet to be present and use it to count time as well. Although we have an almost userland version of gettimeofday() which uses rdtsc in userland, it's not always possible to use it, depending on how broken the multi-socket hardware is. Install the acpi_hpet.h so that applications can use the HPET register definitions. [1] I haven't found a system where HPET's main counter uses more than 32 bit. There seems to be a discrepancy in the Intel documentation (claiming it's a 64-bit counter) and the actual implementation (a 32-bit counter in a 64-bit memory area). MFC after: 1 week Relnotes: yes --- include/Makefile | 4 +- sys/dev/acpica/acpi_hpet.c | 80 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 83 insertions(+), 1 deletion(-) diff --git a/include/Makefile b/include/Makefile index f046bc16fc41..6c7a6a301b35 100644 --- a/include/Makefile +++ b/include/Makefile @@ -159,6 +159,8 @@ copies: cd ${.CURDIR}/../sys/dev/acpica; \ ${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 acpiio.h \ ${DESTDIR}${INCLUDEDIR}/dev/acpica + ${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 acpi_hpet.h \ + ${DESTDIR}${INCLUDEDIR}/dev/acpica cd ${.CURDIR}/../sys/dev/agp; \ ${INSTALL} -C -o ${BINOWN} -g ${BINGRP} -m 444 agpreg.h \ ${DESTDIR}${INCLUDEDIR}/dev/agp @@ -243,7 +245,7 @@ symlinks: done .endfor cd ${.CURDIR}/../sys/dev/acpica; \ - for h in acpiio.h; do \ + for h in acpiio.h acpi_hpet.h; do \ ln -fs ../../../../sys/dev/acpica/$$h \ ${DESTDIR}${INCLUDEDIR}/dev/acpica; \ done diff --git a/sys/dev/acpica/acpi_hpet.c b/sys/dev/acpica/acpi_hpet.c index ae06406d6fbc..9204967da88c 100644 --- a/sys/dev/acpica/acpi_hpet.c +++ b/sys/dev/acpica/acpi_hpet.c @@ -35,11 +35,13 @@ __FBSDID("$FreeBSD$"); #include "opt_apic.h" #endif #include +#include #include #include #include #include #include +#include #include #include #include @@ -106,6 +108,23 @@ struct hpet_softc { char name[8]; } t[32]; int num_timers; + struct cdev *pdev; + int mmap_allow; + int mmap_allow_write; + int devinuse; +}; + +static d_open_t hpet_open; +static d_close_t hpet_close; +static d_mmap_t hpet_mmap; + +static struct cdevsw hpet_cdevsw = { + .d_version = D_VERSION, + .d_flags = D_TRACKCLOSE, + .d_name = "hpet", + .d_open = hpet_open, + .d_close = hpet_close, + .d_mmap = hpet_mmap, }; static u_int hpet_get_timecount(struct timecounter *tc); @@ -317,6 +336,47 @@ hpet_find_irq_rid(device_t dev, u_long start, u_long end) } } +static int +hpet_open(struct cdev *cdev, int oflags, int devtype, struct thread *td) +{ + struct hpet_softc *sc; + + sc = cdev->si_drv1; + if (!sc->mmap_allow) + return (EPERM); + if (atomic_cmpset_32(&sc->devinuse, 0, 1) == 0) + return (EBUSY); + else + return (0); +} + +static int +hpet_close(struct cdev *cdev, int fflag, int devtype, struct thread *td) +{ + struct hpet_softc *sc; + + sc = cdev->si_drv1; + sc->devinuse = 0; + + return (0); +} + +static int +hpet_mmap(struct cdev *cdev, vm_ooffset_t offset, vm_paddr_t *paddr, + int nprot, vm_memattr_t *memattr) +{ + struct hpet_softc *sc; + + sc = cdev->si_drv1; + if (offset > rman_get_size(sc->mem_res)) + return (EINVAL); + if (!sc->mmap_allow_write && (nprot & PROT_WRITE)) + return (EPERM); + *paddr = rman_get_start(sc->mem_res) + offset; + + return (0); +} + /* Discover the HPET via the ACPI table of the same name. */ static void hpet_identify(driver_t *driver, device_t parent) @@ -701,6 +761,26 @@ hpet_attach(device_t dev) maxhpetet++; } } + + sc->pdev = make_dev(&hpet_cdevsw, 0, UID_ROOT, GID_WHEEL, + 0600, "hpet%d", device_get_unit(dev)); + if (sc->pdev) { + sc->pdev->si_drv1 = sc; + sc->mmap_allow = 1; + TUNABLE_INT_FETCH("hw.acpi.hpet.mmap_allow", + &sc->mmap_allow); + sc->mmap_allow_write = 1; + TUNABLE_INT_FETCH("hw.acpi.hpet.mmap_allow_write", + &sc->mmap_allow_write); + SYSCTL_ADD_INT(device_get_sysctl_ctx(dev), + SYSCTL_CHILDREN(device_get_sysctl_tree(dev)), + OID_AUTO, "mmap_allow", + CTLFLAG_RW, &sc->mmap_allow, 0, + "Allow userland to memory map HPET"); + } else + device_printf(dev, "could not create /dev/hpet%d\n", + device_get_unit(dev)); + return (0); }