BSM or Backup Switch Mode is a common feature on RTCs, allowing to select
how the RTC will decide when to switch from its primary power supply to the
backup power supply. It is necessary to be able to set it from userspace as
there are uses cases where it has to be done dynamically.
Supported values are:
RTC_BSM_DISABLED: disabled
RTC_BSM_DIRECT: switching will happen as soon as Vbackup > Vdd
RTC_BSM_LEVEL: switching will happen around a threshold, usually with an
hysteresis
RTC_BSM_STANDBY: switching will not happen until Vdd > Vbackup, this is
useful to ensure the RTC doesn't draw any power until the device is first
powered on.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211018151933.76865-6-alexandre.belloni@bootlin.com
I got a null-ptr-deref report when doing fault injection test:
general protection fault, probably for non-canonical address 0xdffffc0000000022: 0000 [#1] SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000110-0x0000000000000117]
RIP: 0010:device_del+0x132/0xdc0
Call Trace:
cdev_device_del+0x1a/0x80
devm_rtc_unregister_device+0x37/0x80
release_nodes+0xc3/0x3b0
If cdev_device_add() fails, 'dev->p' is not set, it causes
null-ptr-deref when calling cdev_device_del(). Registering
character device is optional, we don't return error code
here, so introduce a new flag 'RTC_NO_CDEV' to indicate
if it has character device, cdev_device_del() is called
when this bit is not set.
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20211011132114.3663509-1-yangyingliang@huawei.com
Introduce a bitfield to allow the drivers to announce the available
features for an RTC.
The main use case would be to better handle alarms, that could be present
or not or have a minute resolution or may need a correct week day to be set.
Use the newly introduced RTC_FEATURE_ALARM bit to then test whether alarms
are available instead of relying on the presence of ops->set_alarm.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210110231752.1418816-2-alexandre.belloni@bootlin.com
Pull RTC updates from Alexandre Belloni:
"Subsystem:
- Remove nvram ABI. There was no complaints about the deprecation for
the last 3 years.
- Improve RTC device allocation and registration
- Now available for ARCH=um
Drivers:
- at91rm9200: correction and sam9x60 support
- ds1307: improve ACPI support
- mxc: now DT only
- pcf2127: watchdog support now needs the reset-source property
- pcf8523: set range
- rx6110: i2c support"
* tag 'rtc-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux: (43 commits)
rtc: pcf2127: only use watchdog when explicitly available
dt-bindings: rtc: add reset-source property
rtc: fix RTC removal
rtc: s3c: Remove dead code related to periodic tick handling
rtc: s3c: Disable all enable (RTC, tick) bits in the probe
rtc: ep93xx: Fix NULL pointer dereference in ep93xx_rtc_read_time
rtc: test: remove debug message
rtc: mxc{,_v2}: enable COMPILE_TEST
rtc: enable RTC framework on ARCH=um
rtc: pcf8523: use BIT
rtc: pcf8523: set range
rtc: pcf8523: switch to devm_rtc_allocate_device
rtc: destroy mutex when releasing the device
rtc: shrink devm_rtc_allocate_device()
rtc: rework rtc_register_device() resource management
rtc: nvmem: emit an error message when nvmem registration fails
rtc: add devm_ prefix to rtc_nvmem_register()
rtc: nvmem: remove nvram ABI
Documentation: list RTC devres helpers in devres.rst
rtc: omap: use devm_pinctrl_register()
...
The current RTC set_offset_nsec value is not really intuitive to
understand.
tsched twrite(t2.tv_sec - 1) t2 (seconds increment)
The offset is calculated from twrite based on the assumption that t2 -
twrite == 1s. That means for the MC146818 RTC the offset needs to be
negative so that the write happens 500ms before t2.
It's easier to understand when the whole calculation is based on t2. That
avoids negative offsets and the meaning is obvious:
t2 - twrite: The time defined by the chip when seconds increment
after the write.
twrite - tsched: The time for the transport to the point where the chip
is updated.
==> set_offset_nsec = t2 - tsched
ttransport = twrite - tsched
tRTCinc = t2 - twrite
==> set_offset_nsec = ttransport + tRTCinc
tRTCinc is a chip property and can be obtained from the data sheet.
ttransport depends on how the RTC is connected. It is close to 0 for
directly accessible RTCs. For RTCs behind a slow bus, e.g. i2c, it's the
time required to send the update over the bus. This can be estimated or
even calibrated, but that's a different problem.
Adjust the implementation and update comments accordingly.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220542.263204937@linutronix.de
rtc_register_device() is a managed interface but it doesn't use devres
by itself - instead it marks an rtc_device as "registered" and the devres
callback for devm_rtc_allocate_device() takes care of resource release.
This doesn't correspond with the design behind devres where managed
structures should not be aware of being managed. The correct solution
here is to register a separate devres callback for unregistering the
device.
While at it: rename rtc_register_device() to devm_rtc_register_device()
and add it to the list of managed interfaces in devres.rst. This way we
can avoid any potential confusion of driver developers who may expect
there to exist a corresponding unregister function.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201109163409.24301-8-brgl@bgdev.pl
There are no users of set_mms and set_mmss64 as they have all been
converted to set_time and are handling the tm to time conversion on their
own.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
The SH RTC is a BCD RTC with some version having 4 digits for the year.
The range for the RTCs with only 2 digits for the year was unfortunately
shifted to handle 1999 to 2098.
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Since commit 416f0e8056 ("RTC: sa1100: Update the sa1100 RTC driver."),
the last user of .read_callback is gone. It has been 8 years and now new
user appeared. Simply remove it.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
All the remaining users of rtc_timers are passing the rtc_device as private
data. Enforce that and rename private_data to rtc.
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Using devm_nvmem_register allows to avoid tracking the nvmem pointer in the
rtc_device structure.
This ultimately allows to register multiple nvmem devices from an RTC
driver.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
devm_rtc_device_unregister is not used by any driver and should not be used
by any new driver.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Move rtc_add_group and rtc_add_groups definition to rtc.h that is available
for all RTC drivers.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Ensure the non managed version of the un/registration functions is not used
anymore. No driver is using it anymore and they should not be necessary.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
