On 32bit platforms, time_t is still a signed 32bit long. If it is
overflowed, userspace and the kernel cant agree on the current system time.
This causes multiple issues, in particular with systemd:
https://github.com/systemd/systemd/issues/1143

A good workaround is to simply avoid using hctosys which is something I
greatly encourage as the time is better set by userspace.

However, many distribution enable it and use systemd which is rendering the
system unusable in case the RTC holds a date after 2038 (and more so after
2106). Many drivers have workaround for this case and they should be
eliminated so there is only one place left to fix when userspace is able to
cope with dates after the 31bit overflow.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always calling rtc_valid_tm after the read_time callback.
It is not necessary to call it just before returning from the callback.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Acked-by: Helge Deller <deller@gmx.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Bit clear operation was missing ~
Signed-off-by: Michael McCormick <michael.mccormick@enatel.net>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

We are now allowing to register debugfs without a valid device, and not
having a valid name will end up using "dummy*" to create debugfs dir.
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

In preparation to enabling -Wvla, remove VLAs and replace them
with fixed-length arrays instead.

>From a security viewpoint, the use of Variable Length Arrays can be
a vector for stack overflow attacks. Also, in general, as the code
evolves it is easy to lose track of how big a VLA can get. Thus, we
can end up having segfaults that are hard to debug.

Also, fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Move this enum to rtc-s5m.c once it is meaningless to others drivers [1].

[1] https://marc.info/?l=linux-rtc&m=152060068925948&w=2Suggested-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

In preparation to enabling -Wvla, remove VLA and replace it
with a fixed-length array instead.

>From a security viewpoint, the use of Variable Length Arrays can be
a vector for stack overflow attacks. Also, in general, as the code
evolves it is easy to lose track of how big a VLA can get. Thus, we
can end up having segfaults that are hard to debug.

Also, fixed as part of the directive to remove all VLAs from
the kernel: https://lkml.org/lkml/2018/3/7/621Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Add commonly used timestamps for range definition.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

From our investigation for all RTC drivers, 1 driver will be expired before
year 2017, 7 drivers will be expired before year 2038, 23 drivers will be
expired before year 2069, 72 drivers will be expired before 2100 and 104
drivers will be expired before 2106. Especially for these early expired
drivers, we need to expand the RTC range to make the RTC can still work
after the expired year.

So we can expand the RTC range by adding one offset to the time when reading
from hardware, and subtracting it when writing back. For example, if you have
an RTC that can do 100 years, and currently is configured to be based in
Jan 1 1970, so it can represents times from 1970 to 2069. Then if you change
the start year from 1970 to 2000, which means it can represents times from
2000 to 2099. By adding or subtracting the offset produced by moving the wrap
point, all times between 1970 and 1999 from RTC hardware could get interpreted
as times from 2070 to 2099, but the interpretation of dates between 2000 and
2069 would not change.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC range validation code can be factored into rtc_valid_range()
function to avoid duplicate code.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Add a way for drivers to inform the core of the supported date/time range.
The core can then check whether the date/time or alarm is in the range
before calling ->set_time, ->set_mmss or ->set_alarm. It returns -ERANGE
when the time is out of range.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Fix possible race condition.
It is not allowed to return with an error code after RTC is registered.
Suggested-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Denis Osterland <Denis.Osterland@diehl.com>
Reviewed-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The interrupt handler got enabled very early. If the interrupt cause is
triggering immediately before the context is fully prepared. This can
lead to undefined behaviour. Therefor we move the interrupt enable code
to the end of the probe function.
Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Denis Osterland <Denis.Osterland@diehl.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Since accessing a Chrome OS EC based rtc is a slow operation, there is a
race window where if the alarm is set for the next second and the second
ticks over right before calculating the alarm offset.

In this case the current driver is setting a 0-second alarm, which would
be considered as disabling alarms by the EC(EC_RTC_ALARM_CLEAR).

This breaks, e.g., hwclock which relies on RTC_UIE_ON ->
rtc_update_irq_enable(), which sets a 1-second alarm and expects it to
fire an interrupt.

So return -ETIME when the alarm is in the past, follow __rtc_set_alarm().
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Tested-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

In order to set time in rtc, need to disable
rtc hw before writing into rtc registers.

Also fixes disabling of alarm while setting
rtc time.
Signed-off-by: Mohit Aggarwal <maggarwa@codeaurora.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

This config select's MFD_SYSCON, but does not depend on HAS_IOMEM.

Compile testing on architecture without HAS_IOMEM causes "unmet
direct dependencies" in Kconfig phase.

Detected by "make ARCH=score allyesconfig".
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The probe function must not fail after rtc_register_device. Also, rename
the nvmem device so it is easily identifiable in /sys/bus/nvmem.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The ISL12026 is a combination RTC and EEPROM device with I2C
interface.  The standard RTC driver interface is provided.  The EEPROM
is accessed via the NVMEM interface.
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The HW default is one tick per second, however instead of assuming this,
lets make sure the waketimer is actually one tick per second before
arming the alarm.
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Justin Chen <justinpopo6@gmail.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The current correction for leap years will fail in 3477. 3476-12-31 being
3477-01-00 because this is 366 leap years after 1970 and 3477 isn't a leap
year.

Fix that by looping over until days is positive or zero.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

This patch fixes a bug, that prevents the Allwinner A83T and the A80
from a successful boot.

The bug is there since v4.16-rc1 and appeared after the clk branch was
merged.

You can find the shortend trace below:

Unable to handle kernel NULL pointer dereference at virtual address
00000000
pgd = (ptrval)
[00000000] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
Modules linked in:
CPU: 0 PID: 49 Comm: kworker/0:1 Not tainted 4.15.0-10190-gb89e32cc #2
Hardware name: Allwinner sun8i Family
Workqueue: events deferred_probe_work_func
PC is at clk_hw_get_rate+0x0/0x34
LR is at ac100_clkout_determine_rate+0x48/0x19c

[ ... ]

(clk_hw_get_rate) from (ac100_clkout_determine_rate+0x48/0x19c)
(ac100_clkout_determine_rate) from  (clk_core_set_rate_nolock+0x3c/0x1a0)
(clk_core_set_rate_nolock) from (clk_set_rate+0x30/0x88)
(clk_set_rate) from (of_clk_set_defaults+0x200/0x364)
(of_clk_set_defaults) from (platform_drv_probe+0x18/0xb0)

To fix that bug, we first check if the return of the
clk_hw_get_parent_by_index is non zero. If it is zero we skip that
clock parent.

The BUG report could be found here: https://lkml.org/lkml/2018/2/10/198

Fixes: 04940631 ("rtc: ac100: Add clk output support")
Signed-off-by: Philipp Rossak <embed3d@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

As per 8.2.6 Setting and reading the time in RTC mode, first stop the clok,
then reset it before setting the date and time registers. Finally, start
the clock.

This uses register address wrap around from 0x2f to 0x00 for efficiency.

This allows to set the clock with a millisecond accuracy (drift is not
corrected in this example):

RTC        System
1325388767 1325388767.000029180
1325388768 1325388768.000018362
1325388769 1325388769.000006544
1325388770 1325388769.999992725
1325388771 1325388770.999974544
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Handle alarms, currently only on INTA
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

This helps debugging as it allows reading registers from debugfs.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

m41t80_get_datetime and m41t80_set_datetime are only used after casting dev
to an i2c_client. Remove that useless indirection.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The IRQ is requested before the struct rtc is allocated and registered, but
this struct is used in the IRQ handler, leading to:

Unable to handle kernel NULL pointer dereference at virtual address 0000017c
pgd = a38a2f9b
[0000017c] *pgd=00000000
Internal error: Oops: 5 [#1] ARM
Modules linked in:
CPU: 0 PID: 613 Comm: irq/48-m41t80 Not tainted 4.16.0-rc1+ #42
Hardware name: Atmel SAMA5
PC is at mutex_lock+0x14/0x38
LR is at m41t80_handle_irq+0x1c/0x9c
pc : [<c06e864c>]    lr : [<c04b70f0>]    psr: 20000013
sp : dec73f30  ip : 00000000  fp : dec56d98
r10: df437cf0  r9 : c0a03008  r8 : c0145ffc
r7 : df5c4300  r6 : dec568d0  r5 : df593000  r4 : 0000017c
r3 : df592800  r2 : 60000013  r1 : df593000  r0 : 0000017c
Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 10c53c7d  Table: 20004059  DAC: 00000051
Process irq/48-m41t80 (pid: 613, stack limit = 0xb52d091e)
Stack: (0xdec73f30 to 0xdec74000)
3f20:                                     dec56840 df5c4300 00000001 df5c4300
3f40: c0145ffc c0146018 dec56840 ffffe000 00000001 c0146290 dec567c0 00000000
3f60: c0146084 ed7c9a62 c014615c dec56d80 dec567c0 00000000 dec72000 dec56840
3f80: c014615c c012ffc0 dec72000 dec567c0 c012fe80 00000000 00000000 00000000
3fa0: 00000000 00000000 00000000 c01010e8 00000000 00000000 00000000 00000000
3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
3fe0: 00000000 00000000 00000000 00000000 00000013 00000000 29282726 2d2c2b2a
[<c06e864c>] (mutex_lock) from [<c04b70f0>] (m41t80_handle_irq+0x1c/0x9c)
[<c04b70f0>] (m41t80_handle_irq) from [<c0146018>] (irq_thread_fn+0x1c/0x54)
[<c0146018>] (irq_thread_fn) from [<c0146290>] (irq_thread+0x134/0x1c0)
[<c0146290>] (irq_thread) from [<c012ffc0>] (kthread+0x140/0x148)
[<c012ffc0>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c)
Exception stack(0xdec73fb0 to 0xdec73ff8)
3fa0:                                     00000000 00000000 00000000 00000000
3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
3fe0: 00000000 00000000 00000000 00000000 00000013 00000000
Code: e3c33d7f e3c3303f f5d0f000 e593300c (e1901f9f)
---[ end trace 22b027302eb7c604 ]---
genirq: exiting task "irq/48-m41t80" (613) is an active IRQ thread (irq 48)

Also, there is another possible race condition. The probe function is not
allowed to fail after the RTC is registered because the following may
happen:

CPU0:                                CPU1:
sys_load_module()
 do_init_module()
  do_one_initcall()
   cmos_do_probe()
    rtc_device_register()
     __register_chrdev()
     cdev->owner = struct module*
                                     open("/dev/rtc0")
    rtc_device_unregister()
  module_put()
  free_module()
   module_free(mod->module_core)
   /* struct module *module is now
      freed */
                                      chrdev_open()
                                       spin_lock(cdev_lock)
                                       cdev_get()
                                        try_module_get()
                                         module_is_live()
                                         /* dereferences already
                                            freed struct module* */

Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc
before requesting the IRQ and register it as late as possible.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

Without CONFIG_RTC_DRV_M41T80_WDT the compiler complains:

|drivers/rtc/rtc-m41t80.c:76 ‘m41t80_rtc_mutex’ defined but not used [-Wunused-variable]

Move the variable to the block where it is used.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

pcf85063_get_datetime and pcf85063_set_datetime are only used after casting
dev to an i2c_client. Remove that useless indirection.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always calling rtc_valid_tm after the read_time callback.
It is not necessary to call it before returning from the callback.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

max6900_i2c_read_time and max6900_i2c_set_time are only used after casting
dev to an i2c_client. Remove that useless indirection.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always calling rtc_valid_tm after the read_time callback.
It is not necessary to call it before returning from the callback.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rs5c372_get_datetime and rs5c372_set_datetime are only used after casting
dev to an i2c_client. Remove that useless indirection.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always calling rtc_valid_tm after the read_time callback.
It is not necessary to call it before returning from the callback.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

It is not necessary to print a message when the time is invalid as
userspace will already get an error (and an optional dev_dbg message).
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

s35390a_set_datetime, s35390a_get_datetime, s35390a_set_alarm and
s35390a_read_alarm are only used after casting dev to an i2c_client. Remove
that useless indirection.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always calling rtc_valid_tm after the read_time callback.
It is not necessary to call it before returning from the callback.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

It is not necessary to print a message when the time is invalid as
userspace will already get an error (and an optional dev_dbg message).
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The probe function is not allowed to fail after registering the RTC because
the following may happen:

CPU0:                                CPU1:
sys_load_module()
 do_init_module()
  do_one_initcall()
   cmos_do_probe()
    rtc_device_register()
     __register_chrdev()
     cdev->owner = struct module*
                                     open("/dev/rtc0")
    rtc_device_unregister()
  module_put()
  free_module()
   module_free(mod->module_core)
   /* struct module *module is now
      freed */
                                      chrdev_open()
                                       spin_lock(cdev_lock)
                                       cdev_get()
                                        try_module_get()
                                         module_is_live()
                                         /* dereferences already
                                            freed struct module* */

Switch to devm_rtc_allocate_device/rtc_register_device to register the rtc
as late as possible.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

At probe time, printing a message when the time is invalid doesn't have
much value. Also, as the comment suggest, this is a leftover from
development wherhe this was used to set the RTc to a default time.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

It is not necessary to print a message when the time is invalid as
userspace will already get an error (and an optional dev_dbg message).
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>