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Sprinkle some arm_isb() to force execution of the mcrr instructions to get

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more accurate values.  (Given that the generic timer is usually running at
a 64th or less of the cpu clock, this only settle to a tick or so.)
This commit is contained in:
matt 2015-03-24 08:58:41 +00:00
parent d87c4ff51d
commit d685920afa
1 changed files with 20 additions and 6 deletions
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26
sys/arch/arm/cortex/gtmr.c
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@ -1,4 +1,4 @@
/* $NetBSD: gtmr.c,v 1.10 2015/03/23 23:33:22 jmcneill Exp $ */
/* $NetBSD: gtmr.c,v 1.11 2015/03/24 08:58:41 matt Exp $ */
/*-
* Copyright (c) 2012 The NetBSD Foundation, Inc.
@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: gtmr.c,v 1.10 2015/03/23 23:33:22 jmcneill Exp $");
__KERNEL_RCSID(0, "$NetBSD: gtmr.c,v 1.11 2015/03/24 08:58:41 matt Exp $");
#include <sys/param.h>
#include <sys/bus.h>
@ -44,6 +44,8 @@ __KERNEL_RCSID(0, "$NetBSD: gtmr.c,v 1.10 2015/03/23 23:33:22 jmcneill Exp $");
#include <prop/proplib.h>
#include <arm/locore.h>
#include <arm/cortex/gtmr_var.h>
#include <arm/cortex/mpcore_var.h>
@ -169,6 +171,7 @@ gtmr_init_cpu_clock(struct cpu_info *ci)
* Get now and update the compare timer.
*/
ci->ci_lastintr = armreg_cntv_ct_read();
arm_isb();
armreg_cntv_tval_write(sc->sc_autoinc);
#if 0
printf("%s: %s: delta cval = %"PRIu64"\n",
@ -186,14 +189,17 @@ gtmr_init_cpu_clock(struct cpu_info *ci)
uint64_t now64;
uint64_t start64 = armreg_cntv_ct_read();
arm_isb();
do {
now64 = armreg_cntv_ct_read();
arm_isb();
} while (start64 == now64);
start64 = now64;
uint64_t end64 = start64 + 64;
uint32_t start32 = armreg_pmccntr_read();
do {
now64 = armreg_cntv_ct_read();
arm_isb();
} while (end64 != now64);
uint32_t end32 = armreg_pmccntr_read();
@ -241,10 +247,11 @@ gtmr_delay(unsigned int n)
const uint64_t delta = n * incr_per_us;
const uint64_t base = armreg_cntv_ct_read();
arm_isb();
const uint64_t finish = base + delta;
while (armreg_cntv_ct_read() < finish) {
/* spin */
arm_isb(); /* spin */
}
}
@ -273,12 +280,16 @@ gtmr_bootdelay(unsigned int ticks)
int
gtmr_intr(void *arg)
{
const uint64_t now = armreg_cntv_ct_read();
struct cpu_info * const ci = curcpu();
uint64_t delta = now - ci->ci_lastintr;
struct clockframe * const cf = arg;
struct gtmr_softc * const sc = &gtmr_sc;
const uint64_t now = armreg_cntv_ct_read();
arm_isb();
uint64_t delta = now - ci->ci_lastintr;
#ifdef DIAGNOSTIC
const uint64_t then = armreg_cntv_cval_read();
struct gtmr_percpu * const pc = percpu_getref(sc->sc_percpu);
@ -329,6 +340,9 @@ setstatclockrate(int newhz)
static u_int
gtmr_get_timecount(struct timecounter *tc)
{
u_int now = (u_int) armreg_cntp_ct_read();
return (u_int) (armreg_cntp_ct_read());
arm_isb(); // we want the time NOW, not some instructions later.
return now;
}