Module Name: src
Committed By: skrll
Date: Wed Oct 25 16:09:46 UTC 2017
Modified Files:
src/sys/arch/arm/cortex: gtmr.c
Log Message:
Improve delay to be better than 1.3 innaccurate by default and handle the
unlikely wrap
To generate a diff of this commit:
cvs rdiff -u -r1.21 -r1.22 src/sys/arch/arm/cortex/gtmr.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/arm/cortex/gtmr.c
diff -u src/sys/arch/arm/cortex/gtmr.c:1.21 src/sys/arch/arm/cortex/gtmr.c:1.22
--- src/sys/arch/arm/cortex/gtmr.c:1.21 Wed Oct 25 16:08:09 2017
+++ src/sys/arch/arm/cortex/gtmr.c Wed Oct 25 16:09:46 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: gtmr.c,v 1.21 2017/10/25 16:08:09 skrll Exp $ */
+/* $NetBSD: gtmr.c,v 1.22 2017/10/25 16:09:46 skrll Exp $ */
/*-
* Copyright (c) 2012 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: gtmr.c,v 1.21 2017/10/25 16:08:09 skrll Exp $");
+__KERNEL_RCSID(0, "$NetBSD: gtmr.c,v 1.22 2017/10/25 16:09:46 skrll Exp $");
#include <sys/param.h>
#include <sys/bus.h>
@@ -245,19 +245,25 @@ gtmr_delay(unsigned int n)
uint32_t freq = sc->sc_freq ? sc->sc_freq : armreg_cnt_frq_read();
KASSERT(freq != 0);
- /*
- * not quite divide by 1000000 but close enough
- * (higher by 1.3% which means we wait 1.3% longer).
- */
- const uint64_t incr_per_us = (freq >> 20) + (freq >> 24);
+ const unsigned int incr_per_us = howmany(freq, 1000000);
+ unsigned int delta = 0, usecs = 0;
arm_isb();
- const uint64_t base = armreg_cntp_ct_read();
- const uint64_t delta = n * incr_per_us;
- const uint64_t finish = base + delta;
+ uint64_t last = armreg_cntp_ct_read();
- while (armreg_cntp_ct_read() < finish) {
- arm_isb(); /* spin */
+ while (n > usecs) {
+ arm_isb();
+ uint64_t curr = armreg_cntp_ct_read();
+ if (curr < last)
+ delta += curr + (UINT64_MAX - last);
+ else
+ delta += curr - last;
+
+ last = curr;
+ if (delta >= incr_per_us) {
+ usecs += delta / incr_per_us;
+ delta %= incr_per_us;
+ }
}
}
