Author: manu
Date: Thu Jun 14 17:18:15 2018
New Revision: 335156
URL: https://svnweb.freebsd.org/changeset/base/335156
Log:
arm timer: Add workaround for Allwinner A64 timer
The timer present in allwinner A64 SoC is unstable, value can jump backward
or forward.
It was found that when bit 11 and upper roll over the low bits can sometimes
being read as all as 1 or all as 0.
Simply ignore the values for those cases.
Modified:
head/sys/arm/arm/generic_timer.c
Modified: head/sys/arm/arm/generic_timer.c
==============================================================================
--- head/sys/arm/arm/generic_timer.c Thu Jun 14 17:09:33 2018
(r335155)
+++ head/sys/arm/arm/generic_timer.c Thu Jun 14 17:18:15 2018
(r335156)
@@ -92,6 +92,7 @@ __FBSDID("$FreeBSD$");
struct arm_tmr_softc {
struct resource *res[4];
void *ihl[4];
+ uint64_t (*get_cntxct)(bool);
uint32_t clkfreq;
struct eventtimer et;
bool physical;
@@ -142,6 +143,28 @@ get_freq(void)
}
static uint64_t
+get_cntxct_a64_unstable(bool physical)
+{
+ uint64_t val
+;
+ isb();
+ if (physical) {
+ do {
+ val = get_el0(cntpct);
+ }
+ while (((val + 1) & 0x7FF) <= 1);
+ }
+ else {
+ do {
+ val = get_el0(cntvct);
+ }
+ while (((val + 1) & 0x7FF) <= 1);
+ }
+
+ return (val);
+}
+
+static uint64_t
get_cntxct(bool physical)
{
uint64_t val;
@@ -226,7 +249,7 @@ static unsigned
arm_tmr_get_timecount(struct timecounter *tc)
{
- return (get_cntxct(arm_tmr_sc->physical));
+ return (arm_tmr_sc->get_cntxct(arm_tmr_sc->physical));
}
static int
@@ -379,6 +402,7 @@ arm_tmr_attach(device_t dev)
if (arm_tmr_sc)
return (ENXIO);
+ sc->get_cntxct = &get_cntxct_a64_unstable;
#ifdef FDT
/* Get the base clock frequency */
node = ofw_bus_get_node(dev);
@@ -387,6 +411,13 @@ arm_tmr_attach(device_t dev)
sizeof(clock));
if (error > 0)
sc->clkfreq = clock;
+
+ if (OF_hasprop(node, "allwinner,sun50i-a64-unstable-timer")) {
+ sc->get_cntxct = &get_cntxct_a64_unstable;
+ if (bootverbose)
+ device_printf(dev,
+ "Enabling allwinner unstable timer
workaround\n");
+ }
}
#endif
@@ -518,10 +549,10 @@ arm_tmr_do_delay(int usec, void *arg)
else
counts = usec * counts_per_usec;
- first = get_cntxct(sc->physical);
+ first = sc->get_cntxct(sc->physical);
while (counts > 0) {
- last = get_cntxct(sc->physical);
+ last = sc->get_cntxct(sc->physical);
counts -= (int32_t)(last - first);
first = last;
}
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