git: 00d061855deb - main - Garbage-collect ACPI-safe timer and friends
Date: Fri, 21 Jun 2024 07:19:30 UTC
The branch main has been updated by cperciva:
URL: https://cgit.FreeBSD.org/src/commit/?id=00d061855deb93df5d709c8a794985ebb55012f8
commit 00d061855deb93df5d709c8a794985ebb55012f8
Author: Colin Percival <cperciva@FreeBSD.org>
AuthorDate: 2024-06-21 07:06:48 +0000
Commit: Colin Percival <cperciva@FreeBSD.org>
CommitDate: 2024-06-21 07:19:08 +0000
Garbage-collect ACPI-safe timer and friends
In 2001 when the ACPI timer was introduced, it included code to check
for a bug present in some Pentium II and Pentium III chipsets; if the
bug was found to be present, ACPI-safe (which was slower but had a
workaround for the bug) would be used rather than ACPI-fast (which
read the same timer but without the workaround).
In a8b89dff6ac0 (September 2021) I disabled this check by default,
with a loader tunable available to re-enable it; I announced at the
time that it would go away in FreeBSD 15 if I didn't receive any
reports of problems. I have received no such problems, so this code
is now going away.
The debug.acpi.timer_test loader variable triggered a lengthy (in fact,
infinitely long) test of the ACPI timer and appears to have been
introduced as part of the process of writing the ACPI timer (and the
associated ACPI-safe workaround) in 2001; since we are dropping support
for systems with this ACPI bug, there is no need to keep that test code
either.
---
sys/dev/acpica/acpi_timer.c | 126 ++------------------------------------------
1 file changed, 3 insertions(+), 123 deletions(-)
diff --git a/sys/dev/acpica/acpi_timer.c b/sys/dev/acpica/acpi_timer.c
index e78b4728749a..13a89c4e6154 100644
--- a/sys/dev/acpica/acpi_timer.c
+++ b/sys/dev/acpica/acpi_timer.c
@@ -74,11 +74,6 @@ static void acpi_timer_suspend_handler(struct timecounter *);
static u_int acpi_timer_get_timecount(struct timecounter *tc);
static u_int acpi_timer_get_timecount_safe(struct timecounter *tc);
static int acpi_timer_sysctl_freq(SYSCTL_HANDLER_ARGS);
-static void acpi_timer_boot_test(void);
-
-static int acpi_timer_test(void);
-static int acpi_timer_test_enabled = 0;
-TUNABLE_INT("hw.acpi.timer_test_enabled", &acpi_timer_test_enabled);
static device_method_t acpi_timer_methods[] = {
DEVMETHOD(device_identify, acpi_timer_identify),
@@ -192,8 +187,6 @@ acpi_timer_probe(device_t dev)
acpi_timer_timecounter.tc_counter_mask = 0x00ffffff;
acpi_timer_timecounter.tc_frequency = acpi_timer_frequency;
acpi_timer_timecounter.tc_flags = TC_FLAGS_SUSPEND_SAFE;
- if (testenv("debug.acpi.timer_test"))
- acpi_timer_boot_test();
/*
* If all tests of the counter succeed, use the ACPI-fast method. If
@@ -203,19 +196,11 @@ acpi_timer_probe(device_t dev)
j = 0;
if (bootverbose)
printf("ACPI timer:");
- for (i = 0; i < 10; i++)
- j += acpi_timer_test();
if (bootverbose)
printf(" -> %d\n", j);
- if (j == 10) {
- acpi_timer_timecounter.tc_name = "ACPI-fast";
- acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount;
- acpi_timer_timecounter.tc_quality = 900;
- } else {
- acpi_timer_timecounter.tc_name = "ACPI-safe";
- acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount_safe;
- acpi_timer_timecounter.tc_quality = 850;
- }
+ acpi_timer_timecounter.tc_name = "ACPI-fast";
+ acpi_timer_timecounter.tc_get_timecount = acpi_timer_get_timecount;
+ acpi_timer_timecounter.tc_quality = 900;
tc_init(&acpi_timer_timecounter);
device_set_descf(dev, "%d-bit timer at %u.%06uMHz",
@@ -368,108 +353,3 @@ SYSCTL_PROC(_machdep, OID_AUTO, acpi_timer_freq,
CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 0,
acpi_timer_sysctl_freq, "I",
"ACPI timer frequency");
-
-/*
- * Some ACPI timers are known or believed to suffer from implementation
- * problems which can lead to erroneous values being read. This function
- * tests for consistent results from the timer and returns 1 if it believes
- * the timer is consistent, otherwise it returns 0.
- *
- * It appears the cause is that the counter is not latched to the PCI bus
- * clock when read:
- *
- * ] 20. ACPI Timer Errata
- * ]
- * ] Problem: The power management timer may return improper result when
- * ] read. Although the timer value settles properly after incrementing,
- * ] while incrementing there is a 3nS window every 69.8nS where the
- * ] timer value is indeterminate (a 4.2% chance that the data will be
- * ] incorrect when read). As a result, the ACPI free running count up
- * ] timer specification is violated due to erroneous reads. Implication:
- * ] System hangs due to the "inaccuracy" of the timer when used by
- * ] software for time critical events and delays.
- * ]
- * ] Workaround: Read the register twice and compare.
- * ] Status: This will not be fixed in the PIIX4 or PIIX4E, it is fixed
- * ] in the PIIX4M.
- */
-#define N 2000
-static int
-acpi_timer_test(void)
-{
- uint32_t last, this;
- int delta, max, max2, min, n;
- register_t s;
-
- /* Skip the test based on the hw.acpi.timer_test_enabled tunable. */
- if (!acpi_timer_test_enabled)
- return (1);
-
- TSENTER();
-
- min = INT32_MAX;
- max = max2 = 0;
-
- /* Test the timer with interrupts disabled to get accurate results. */
- s = intr_disable();
- last = acpi_timer_read();
- for (n = 0; n < N; n++) {
- this = acpi_timer_read();
- delta = acpi_TimerDelta(this, last);
- if (delta > max) {
- max2 = max;
- max = delta;
- } else if (delta > max2)
- max2 = delta;
- if (delta < min)
- min = delta;
- last = this;
- }
- intr_restore(s);
-
- delta = max2 - min;
- if ((max - min > 8 || delta > 3) && vm_guest == VM_GUEST_NO)
- n = 0;
- else if (min < 0 || max == 0 || max2 == 0)
- n = 0;
- else
- n = 1;
- if (bootverbose)
- printf(" %d/%d", n, delta);
-
- TSEXIT();
-
- return (n);
-}
-#undef N
-
-/*
- * Test harness for verifying ACPI timer behaviour.
- * Boot with debug.acpi.timer_test set to invoke this.
- */
-static void
-acpi_timer_boot_test(void)
-{
- uint32_t u1, u2, u3;
-
- u1 = acpi_timer_read();
- u2 = acpi_timer_read();
- u3 = acpi_timer_read();
-
- device_printf(acpi_timer_dev, "timer test in progress, reboot to quit.\n");
- for (;;) {
- /*
- * The failure case is where u3 > u1, but u2 does not fall between
- * the two, ie. it contains garbage.
- */
- if (u3 > u1) {
- if (u2 < u1 || u2 > u3)
- device_printf(acpi_timer_dev,
- "timer is not monotonic: 0x%08x,0x%08x,0x%08x\n",
- u1, u2, u3);
- }
- u1 = u2;
- u2 = u3;
- u3 = acpi_timer_read();
- }
-}