Hi,
> You really need to update the “should skip” logic for this. It should
> probably be changed to something along the lines of:
>
> - If todr handle has NULL dev, consider it to be the authoritative TODR (it
> is likely backed by a CPU register [vax] or a firmware call [like EFI]).
>
> - Otherwise, If the DEVICE_IS_SYSTEM_TODR device call returns true, the
> consider it to be the authoritative TODR.
>
> - The authoiritative TODR should be at the head of the list, everything else
> added in disovered order after.
>
> IMO, it would be better to not dynamically allocate memory for this. Just
> but the list linkage in the todr handle and bump the kernel version?
Thanks for the comments! How about something closer to the attached?
I replaced the "should skip" logic with a todr_is_system() check instead.
If an RTC is probed after the first, and this returns true, then that RTC
is moved to the head of the list.
I don't have any machines with no device backing the RTC, nor with a
binding for DEVICE_IS_SYSTEM_TODR to test against though. Looking at the
code for DEVICE_IS_SYSTEM_TODR, I wonder about extending it for machines
which don't use device tree. However, this would probably have to be
something in the individual drivers configured from a kernel flag or based
on a firmware property. Would that make sense?
Does it need a kernel version bump? None of the externally visible
functions have changed signatures.
With this patch, dmesg from a Sun V245 with 2 RTC's looks like:
[ 1.000000] rtc0 at ebus0 addr 70-73: mc146818 compatible time-of-day
clock: m5823
...
[ 1.000000] dsrtc0 at iic0 addr 0x68: DS1307 Real-time Clock/NVRAM
[ 1.000000] dsrtc0: secondary clock
Regards,
Julian
- - - - - 8< - - - - - - - - - - - - - - - - - - - - - - - - - 8< - - - - - -
Index: src/sys/kern/kern_todr.c
===================================================================
RCS file: /cvsroot/src/sys/kern/kern_todr.c,v
retrieving revision 1.52
diff -u -r1.52 kern_todr.c
--- src/sys/kern/kern_todr.c 4 Jan 2026 02:09:03 -0000 1.52
+++ src/sys/kern/kern_todr.c 22 Sep 2026 09:50:02 -0000
@@ -78,6 +78,7 @@
#include <sys/device_calls.h>
#include <sys/intr.h>
#include <sys/kernel.h>
+#include <sys/kmem.h>
#include <sys/mutex.h>
#include <sys/rndsource.h>
#include <sys/sdt.h>
@@ -86,11 +87,18 @@
#include <dev/clock_subr.h> /* hmm.. this should probably move to sys */
+struct todr_list {
+ todr_chip_handle_t todr_handle;
+ struct todr_list *todr_next;
+};
+static const char default_name[] = "internal ";
+
static int todr_gettime(todr_chip_handle_t, struct timeval *);
static int todr_settime(todr_chip_handle_t, struct timeval *);
static kmutex_t todr_mutex;
-static todr_chip_handle_t todr_handle;
+static struct todr_list todr_head =
+ { .todr_handle = NULL, .todr_next = NULL };
static bool todr_initialized;
/* The minimum reasonable RTC date before preposterousness */
@@ -143,33 +151,32 @@
}
/*
- * todr_should_skip:
- * Evaluate if we should skip attaching the clock device
- * specified by the todr handle.
+ * todr_is_system:
+ * Evaluate if the clock device specified by the todr handle
+ * is the system clock.
*/
static bool
-todr_should_skip(todr_chip_handle_t todr)
+todr_is_system(todr_chip_handle_t todr)
{
device_t dev = todr->todr_dev;
struct device_is_system_todr_args args = { };
- /* No basis for evaluation if no device backs the TODR. */
+ /* Assume this is the system clock if no device backs the TODR. */
if (dev == NULL) {
- return false;
+ return true;
}
if (device_call(dev, DEVICE_IS_SYSTEM_TODR(&args)) != 0) {
- /* Call is not supported; proceed as if we should attach. */
+ /* Call is not supported. */
return false;
}
if (args.result) {
- /* This is the system TODR; proceed. */
- return false;
+ /* This is the system TODR. */
+ return true;
}
- aprint_normal_dev(dev, "disabled (not system TODR)\n");
- return true;
+ return false;
}
/*
@@ -179,6 +186,9 @@
void
todr_attach(todr_chip_handle_t todr)
{
+ struct todr_list *todr_newp, *todr_iterp;
+ bool is_system;
+ const char *dev_name;
/*
* todr_init() is called very early in main(), but this is
@@ -187,18 +197,40 @@
*/
KASSERT(todr_initialized);
- if (todr_should_skip(todr)) {
- return;
- }
+ is_system = todr_is_system(todr);
- todr_lock();
- if (todr_handle) {
+ /* Initial entry is static, others allocated. */
+ if (todr_head.todr_handle == NULL) {
+ todr_lock();
+ todr_head.todr_handle = todr;
todr_unlock();
- printf("todr_attach: TOD already configured\n");
- return;
+ } else {
+ todr_newp = kmem_alloc(sizeof(struct todr_list),
+ KM_SLEEP);
+ todr_newp->todr_next = NULL;
+ todr_lock();
+ /* Move the system TODR to the head of the list */
+ if (is_system) {
+ todr_newp->todr_handle = todr_head.todr_handle;
+ todr_head.todr_handle = todr;
+ } else {
+ todr_newp->todr_handle = todr;
+ }
+ todr_iterp = &todr_head;
+ while (todr_iterp->todr_next != NULL)
+ todr_iterp = todr_iterp->todr_next;
+ todr_iterp->todr_next = todr_newp;
+ todr_unlock();
+
+ if (todr->todr_dev == NULL)
+ dev_name = default_name;
+ else
+ dev_name = device_xname(todr->todr_dev);
+ if (is_system)
+ printf("%s: system clock\n", dev_name);
+ else
+ printf("%s: secondary clock\n", dev_name);
}
- todr_handle = todr;
- todr_unlock();
}
static bool timeset = false;
@@ -217,7 +249,11 @@
bool goodtime = false;
bool badrtc = false;
struct timespec ts;
- struct timeval tv;
+ struct timeval tv, tv2;
+ struct todr_list *todr_iterp;
+ device_t t_dev;
+ const char *dev_name;
+ time_t deltat;
KASSERT(todr_lock_owned());
@@ -246,22 +282,23 @@
/*
* Some ports need to be supplied base in order to fabricate a time_t.
*/
- if (todr_handle)
- todr_handle->todr_base_time = base;
+ if (todr_head.todr_handle != NULL)
+ todr_head.todr_handle->todr_base_time = base;
memset(&tv, 0, sizeof(tv));
- if ((todr_handle == NULL) ||
- (todr_gettime(todr_handle, &tv) != 0) ||
+ /* Note, that we use the first RTC for system time. */
+ if ((todr_head.todr_handle == NULL) ||
+ (todr_gettime(todr_head.todr_handle, &tv) != 0) ||
(tv.tv_sec < (PREPOSTEROUS_YEARS * SECS_PER_COMMON_YEAR))) {
- if (todr_handle != NULL)
+ if (todr_head.todr_handle != NULL)
printf("WARNING: preposterous TOD clock time\n");
else
printf("WARNING: no TOD clock present\n");
badrtc = true;
} else {
- time_t deltat = tv.tv_sec - base;
+ deltat = tv.tv_sec - base;
if (deltat < 0)
deltat = -deltat;
@@ -301,6 +338,33 @@
tv.tv_usec = 0;
}
+ /* Check other clocks, if any, against our time */
+ todr_iterp = &todr_head;
+ while ((todr_iterp = todr_iterp->todr_next) != NULL) {
+ if ((todr_iterp->todr_handle == NULL) ||
+ (todr_gettime(todr_iterp->todr_handle, &tv2) != 0))
+ continue;
+ t_dev = todr_iterp->todr_handle->todr_dev;
+ if (t_dev == NULL)
+ dev_name = default_name;
+ else
+ dev_name = device_xname(t_dev);
+ if (tv2.tv_sec < (PREPOSTEROUS_YEARS * SECS_PER_COMMON_YEAR)) {
+ printf("WARNING: preposterous %s clock time\n",
+ dev_name);
+ deltat = 0;
+ } else {
+ deltat = tv.tv_sec - tv2.tv_sec;
+ rnd_add_data(NULL, &tv, sizeof(tv), 0);
+ }
+ if (deltat < -10)
+ printf("WARNING: %s clock lost %" PRId64 " seconds\n",
+ dev_name, deltat);
+ if (deltat > 10)
+ printf("WARNING: %s clock gained %" PRId64 " seconds\n",
+ dev_name, deltat);
+ }
+
timeset = true;
ts.tv_sec = tv.tv_sec;
@@ -315,13 +379,16 @@
/*
* todr_save_systime:
- * Save the current system time back to the TOD clock.
+ * Save the current system time back to the TOD clock(s).
* Must be called with the TODR lock held.
*/
void
todr_save_systime(void)
{
struct timeval tv;
+ struct todr_list *todr_iterp;
+ device_t t_dev;
+ const char *dev_name;
KASSERT(todr_lock_owned());
@@ -338,9 +405,19 @@
if (tv.tv_sec == 0)
return;
- if (todr_handle)
- if (todr_settime(todr_handle, &tv) != 0)
- printf("Cannot set TOD clock time\n");
+ todr_iterp = &todr_head;
+ do {
+ if ((todr_iterp->todr_handle != NULL) &&
+ (todr_settime(todr_iterp->todr_handle, &tv) != 0)) {
+ t_dev = todr_iterp->todr_handle->todr_dev;
+ if (t_dev == NULL)
+ dev_name = default_name;
+ else
+ dev_name = device_xname(t_dev);
+ printf("Cannot set %s TOD clock time\n", dev_name);
+ }
+ todr_iterp = todr_iterp->todr_next;
+ } while (todr_iterp != NULL);
}
/*
--
