The offset which is used to steer the start of an RTC synchronization
update via rtc_set_ntp_time() is huge. The math behind this is:
tsched twrite(t2.tv_sec - 1) t2 (seconds increment)
twrite - tsched is the transport time for the write to hit the device.
t2 - twrite depends on the chip and is for most chips one second.
The rtc_set_ntp_time() calculation of tsched is:
tsched = t2 - 1sec - (t2 - twrite)
The default for the sync offset is 500ms which means that twrite - tsched
is 500ms assumed that t2 - twrite is one second.
This is 0.5 seconds off for RTCs which are directly accessible by IO writes
and probably for the majority of i2C/SPI based RTC off by an order of
magnitude. Set it to 5ms which should bring it closer to reality.
The default can be adjusted by drivers (rtc_cmos does so) and could be
adjusted further by a calibration method which is an orthogonal problem.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220541.960333166@linutronix.de
The offset for rtc_cmos must be -500ms to work correctly with the current
implementation of rtc_set_ntp_time() due to the following:
tsched twrite(t2.tv_sec - 1) t2 (seconds increment)
twrite - tsched is the transport time for the write to hit the device,
which is negligible for this chip because it's accessed directly.
t2 - twrite = 500ms according to the datasheet.
But rtc_set_ntp_time() calculation of tsched is:
tsched = t2 - 1sec - (t2 - twrite)
The default for the sync offset is 500ms which means that the write happens
at t2 - 1.5 seconds which is obviously off by a second for this device.
Make the offset -500ms so it works correct.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220541.830517160@linutronix.de
The MC146818 driver is prone to read garbage from the RTC. There are
several issues all related to the update cycle of the MC146818. The chip
increments seconds obviously once per second and indicates that by a bit in
a register. The bit goes high 244us before the actual update starts. During
the update the readout of the time values is undefined.
The code just checks whether the update in progress bit (UIP) is set before
reading the clock. If it's set it waits arbitrary 20ms before retrying,
which is ample because the maximum update time is ~2ms.
But this check does not guarantee that the UIP bit goes high and the actual
update happens during the readout. So the following can happen
0.997 UIP = False
-> Interrupt/NMI/preemption
0.998 UIP -> True
0.999 Readout <- Undefined
To prevent this rework the code so it checks UIP before and after the
readout and if set after the readout try again.
But that's not enough to cover the following:
0.997 UIP = False
Readout seconds
-> NMI (or vCPU scheduled out)
0.998 UIP -> True
update completes
UIP -> False
1.000 Readout minutes,....
UIP check succeeds
That can make the readout wrong up to 59 seconds.
To prevent this, read the seconds value before the first UIP check,
validate it after checking UIP and after reading out the rest.
It's amazing that the original i386 code had this actually correct and
the generic implementation of the MC146818 driver got it wrong in 2002 and
it stayed that way until today.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201206220541.594826678@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
Some users check the return value of devm_rtc_nvmem_register() only in
order to emit an error message and then continue probing. This is fine
as an rtc can function without exposing nvmem but let's generalize it:
let's make the registration function emit the error message so that
users don't have to.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201109163409.24301-7-brgl@bgdev.pl
The RTC core only reads the alarm from the hardware at boot time, to know
whether an alarm was already set before booting. It keeps track of all the
alarms after that so there is no need to ever read the auxiliary alarm.
Commit 3822d1bb0d ("rtc: sc27xx: Always read normal alarm when
registering RTC device") already effectively removed the capability to read
the auxiliary alarm as .read_alarm is always called with rtc->registered set
to false.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Reviewed-by: Chunyan Zhang <zhang.lyra@gmail.com>
Link: https://lore.kernel.org/r/20201117212201.1288608-1-alexandre.belloni@bootlin.com
Enable wakeup in the hym8563 driver if the IRQ was successfully
requested or if wakeup-source is set in the devicetree.
As per the description of device_init_wakeup(), it should be enabled
for "devices that everyone expects to be wakeup sources". One would
expect this to be the case with a real-time clock.
Tested on rk3288-rock2-square, which has an IRQ configured for the
RTC. As a result, wakeup was enabled during driver initialisation.
Fixes: dcaf038493 ("rtc: add hym8563 rtc-driver")
Reported-by: kernelci.org bot <bot@kernelci.org>
Signed-off-by: Guillaume Tucker <guillaume.tucker@collabora.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1ea023e2ba50a4dab6e39be93d7de3146af71a60.1604653374.git.guillaume.tucker@collabora.com
These functions should return zero on success. Non-zero returns are
treated as error. On some paths, this doesn't matter but in
nvmem_cell_read() a non-zero return would be passed to ERR_PTR() and
lead to an Oops.
Fixes: d6c3029f32 ("rtc: pcf2127: add support for accessing internal static RAM")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201022070451.GA2817669@mwanda
Pull RTC updates from Alexandre Belloni:
"A new driver this cycle is making the bulk of the changes and the
rx8010 driver has been rework to use the modern APIs.
Summary:
Subsystem:
- new generic DT properties: aux-voltage-chargeable,
trickle-voltage-millivolt
New driver:
- Microcrystal RV-3032
Drivers:
- ds1307: use aux-voltage-chargeable
- r9701, rx8010: modernization of the driver
- rv3028: fix clock output, trickle resistor values, RAM
configuration registers"
* tag 'rtc-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux: (50 commits)
rtc: r9701: set range
rtc: r9701: convert to devm_rtc_allocate_device
rtc: r9701: stop setting RWKCNT
rtc: r9701: remove useless memset
rtc: r9701: stop setting a default time
rtc: r9701: remove leftover comment
rtc: rv3032: Add a driver for Microcrystal RV-3032
dt-bindings: rtc: rv3032: add RV-3032 bindings
dt-bindings: rtc: add trickle-voltage-millivolt
rtc: rv3028: ensure ram configuration registers are saved
rtc: rv3028: factorize EERD bit handling
rtc: rv3028: fix trickle resistor values
rtc: rv3028: fix clock output support
rtc: mt6397: Remove unused member dev
rtc: rv8803: simplify the return expression of rv8803_nvram_write
rtc: meson: simplify the return expression of meson_vrtc_probe
rtc: rx8010: rename rx8010_init_client() to rx8010_init()
rtc: ds1307: enable rx8130's backup battery, make it chargeable optionally
rtc: ds1307: consider aux-voltage-chargeable
rtc: ds1307: store previous charge default per chip
...
