linux/drivers/rtc, branch v5.11

rtc: mc146818: Dont test for bit 0-5 in Register D

2021-02-02T19:35:02Z

The recent change to validate the RTC turned out to be overly tight. While it cures the problem on the reporters machine it breaks machines with Intel chipsets which use bit 0-5 of the D register. So check only for bit 6 being 0 which is the case on these Intel machines as well. Fixes: 211e5db19d15 ("rtc: mc146818: Detect and handle broken RTCs") Reported-by: Serge Belyshev Reported-by: Dirk Gouders Reported-by: Borislav Petkov Signed-off-by: Thomas Gleixner Tested-by: Dirk Gouders Tested-by: Len Brown Tested-by: Borislav Petkov Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/87zh0nbnha.fsf@nanos.tec.linutronix.de

rtc: mc146818: Detect and handle broken RTCs

2021-01-27T08:36:22Z

The recent fix for handling the UIP bit unearthed another issue in the RTC code. If the RTC is advertised but the readout is straight 0xFF because it's not available, the old code just proceeded with crappy values, but the new code hangs because it waits for the UIP bit to become low. Add a sanity check in the RTC CMOS probe function which reads the RTC_VALID register (Register D) which should have bit 0-6 cleared. If that's not the case then fail to register the CMOS. Add the same check to mc146818_get_time(), warn once when the condition is true and invalidate the rtc_time data. Reported-by: Mickaël Salaün Signed-off-by: Thomas Gleixner Tested-by: Mickaël Salaün Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/87tur3fx7w.fsf@nanos.tec.linutronix.de

Merge tag 'rtc-5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux

2020-12-20T18:12:06Z

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() ...

rtc: pcf2127: only use watchdog when explicitly available

2020-12-19T00:57:44Z

Most boards using the pcf2127 chip (in my bubble) don't make use of the watchdog functionality and the respective output is not connected. The effect on such a board is that there is a watchdog device provided that doesn't work. So only register the watchdog if the device tree has a "reset-source" property. Signed-off-by: Uwe Kleine-König [RV: s/has-watchdog/reset-source/] Signed-off-by: Rasmus Villemoes Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20201218101054.25416-3-rasmus.villemoes@prevas.dk

rtc: fix RTC removal

2020-12-15T23:33:33Z

Since the rtc_register_device, removing an RTC device will end with a refcount_t: underflow; use-after-free warning since put_device is called twice in the device tear down path. Fixes: fdcfd854333b ("rtc: rework rtc_register_device() resource management") Signed-off-by: Alexandre Belloni Reviewed-by: Bartosz Golaszewski Link: https://lore.kernel.org/r/20201205231449.610980-1-alexandre.belloni@bootlin.com

ntp: Make the RTC sync offset less obscure

2020-12-11T09:40:53Z

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 Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/20201206220542.263204937@linutronix.de

ntp, rtc: Move rtc_set_ntp_time() to ntp code

2020-12-11T09:40:52Z

rtc_set_ntp_time() is not really RTC functionality as the code is just a user of RTC. Move it into the NTP code which allows further cleanups. Requested-by: Alexandre Belloni Signed-off-by: Thomas Gleixner Reviewed-by: Jason Gunthorpe Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/20201206220542.166871172@linutronix.de

rtc: core: Make the sync offset default more realistic

2020-12-11T09:40:52Z

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 Reviewed-by: Jason Gunthorpe Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/20201206220541.960333166@linutronix.de

rtc: cmos: Make rtc_cmos sync offset correct

2020-12-11T09:40:52Z

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 Reviewed-by: Jason Gunthorpe Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/20201206220541.830517160@linutronix.de

rtc: mc146818: Reduce spinlock section in mc146818_set_time()

2020-12-11T09:40:52Z

No need to hold the lock and disable interrupts for doing math. Signed-off-by: Thomas Gleixner Acked-by: Alexandre Belloni Link: https://lore.kernel.org/r/20201206220541.709243630@linutronix.de