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>

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>

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>

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 RTC core is always validating the rtc_time struct before calling
.set_time. It is not necessary to do it again in .set_time.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always validating the rtc_time struct before calling
.set_time or .set_alarm. It is not necessary to do it again.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

The RTC core is always validating the rtc_time struct before calling
.set_time or .set_alarm. It is not necessary to do it again.
Also, rtc_time_to_tm never generates an invalid rtc_tm (it can be out of
range though).
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>

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>

isl12022_get_datetime and isl12022_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>

rtc_time64_to_tm never generates an invalid tm. It is not necessary to
validate it. Also, the RTC core is always calling rtc_valid_tm after the
read_time callback.
Reviewed-by: Baolin Wang <baolin.wang@linaro.org>
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>

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>

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.
Acked-by: Steve Twiss <stwiss.opensource@diasemi.com>
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.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
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>

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>

rtc_time_to_tm never generates an invalid tm. It is not necessary to
validate it.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc_time64_to_tm never generates an invalid tm. It is not necessary to
validate it.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>