rtc: snvs: Allow a time difference on clock register read

On an iMX6ULL the following message appears when a wakealarm is set:

echo 0 > /sys/class/rtc/rtc1/wakealarm
rtc rtc1: Timeout trying to get valid LPSRT Counter read

This does not always happen but is reproducible quite often (7 out of 10
times). The problem appears because the iMX6ULL is not able to read the
registers within one 32kHz clock cycle which is the base clock of the
RTC. Therefore, this patch allows a difference of up to 320 cycles
(10ms). 10ms was chosen to be big enough even on systems with less cpu
power (e.g. iMX6ULL). According to the reference manual a difference is
fine:
- If the two consecutive reads are similar, the value is correct.
The values have to be similar, not equal.

Fixes: cd7f3a249dbe ("rtc: snvs: Add timeouts to avoid kernel lockups")
Reviewed-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Signed-off-by: Stefan Eichenberger <stefan.eichenberger@toradex.com>
Signed-off-by: Francesco Dolcini <francesco@dolcini.it>
Link: https://lore.kernel.org/r/20221106115915.7930-1-francesco@dolcini.it
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: rework rtc_register_device() resource management

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

rtc: snvs: Remove NULL pointer check before clk_*

Because clk_* already checked NULL clock parameter,
so the additional checks are unnecessary, just remove them.

Signed-off-by: Xu Wang <vulab@iscas.ac.cn>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201113080305.65961-1-vulab@iscas.ac.cn

rtc: snvs: Add necessary clock operations for RTC APIs

There could be still RTC registers access after RTC suspend
with clock disabled, need to add clock operations for each
RTC API to make sure accessing RTC registers is successfully.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1590113996-31845-2-git-send-email-Anson.Huang@nxp.com

rtc: snvs: Make SNVS clock always prepared

In IRQ handler, ONLY clock enable/disable is called due to
clock prepare can NOT be called in interrupt context, but
clock enable/disable will return failure if prepare count
is 0, to fix this issue, just make SNVS clock always prepared
there, the SNVS clock has no prepare function implemented,
so it won't impact anything.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/1590113996-31845-1-git-send-email-Anson.Huang@nxp.com

rtc: snvs: Use devm_add_action_or_reset() for calls to clk_disable_unprepare()

Use devm_add_action_or_reset() for calls to clk_disable_unprepare(),
which can simplify the error handling.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/1584109849-21402-1-git-send-email-Anson.Huang@nxp.com
Link: https://lore.kernel.org/r/1584233264-26025-1-git-send-email-Anson.Huang@nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: Remove unused include of of_device.h

There is nothing in use from of_device.h, remove it.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/1581823666-16944-1-git-send-email-Anson.Huang@nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: switch to rtc_time64_to_tm/rtc_tm_to_time64

Call the 64bit versions of rtc_tm time conversion now that the range is
enforced by the core.

Link: https://lore.kernel.org/r/20190828205056.31321-2-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: set range

The SNVS is a 47-bit counter incremented at 32768Hz, it is then a 32-bit
second counter.

Link: https://lore.kernel.org/r/20190828205056.31321-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: fix possible race condition

The RTC IRQ is requested before the struct rtc_device is allocated,
this may lead to a NULL pointer dereference in IRQ handler.

To fix this issue, allocating the rtc_device struct before requesting
the RTC IRQ using devm_rtc_allocate_device, and use rtc_register_device
to register the RTC device.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/20190716071858.36750-1-Anson.Huang@nxp.com
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: Use __maybe_unused instead of #if CONFIG_PM_SLEEP

Use __maybe_unused for power management related functions
instead of #if CONFIG_PM_SLEEP to simply the code.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: use devm_platform_ioremap_resource() to simplify code

Use the new helper devm_platform_ioremap_resource() which wraps the
platform_get_resource() and devm_ioremap_resource() together, to
simplify the code.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: use dev_pm_set_wake_irq() to simplify code

With calling dev_pm_set_wake_irq() to set SNVS RTC as wakeup
source for suspend, generic wake irq mechanism will automatically
enable it as wakeup source when suspend, then the suspend/resume
callback which are ONLY for enabling/disabling irq wake can be
removed, it simplifies the code.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: make sure clock is enabled for interrupt handle

During system suspend, the SNVS RTC's clock will be disabled in
noirq suspend phase, but SNVS RTC's alarm interrupt could still
arrive, system will hang if SNVS RTC driver tries to access register
without clock enabled, this patch fixes the issue of this scenario.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: Add timeouts to avoid kernel lockups

In order to read correctly from asynchronously updated RTC registers,
it's necessary to read repeatedly until their values do not change from
read to read. It's also necessary to wait for three RTC clock ticks for
certain operations. There are no timeouts in this code and these
operations could possibly loop forever.

To avoid kernel hangs, put in timeouts.

The iMX7d can be configured to stop the SRTC on a tamper event, which
will lockup the kernel inside this driver as described above.

These hangs can happen when running under qemu, which doesn't emulate
the SNVS RTC, though currently the driver will refuse to load on qemu
due to a timeout in the driver probe method.

It could also happen if the SRTC block where somehow placed into reset
or the slow speed clock that drives the SRTC counter (but not the CPU)
were to stop.

The symptoms on a two core iMX7d are a work queue hang on
rtc_timer_do_work(), which eventually blocks a systemd fsnotify
operation that triggers a work queue flush, causing systemd to hang and
thus causing all services that should be started by systemd, like a
console getty, to fail to start or stop.

Also optimize the wait code to wait less. It only needs to wait for the
clock to advance three ticks, not to see it change three times.

Cc: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Signed-off-by: Trent Piepho <tpiepho@impinj.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: Switch to SPDX identifier

Adopt the SPDX license identifier headers to ease license compliance
management.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: Fix usage of snvs_rtc_enable

commit 179a502f8c46 ("rtc: snvs: add Freescale rtc-snvs driver") introduces
the SNVS RTC driver with a function snvs_rtc_enable().

snvs_rtc_enable() can return an error on the enable path however this
driver does not currently trap that failure on the probe() path and
consequently if enabling the RTC fails we encounter a later error spinning
forever in rtc_write_sync_lp().

[ 36.093481] [<c010d630>] (__irq_svc) from [<c0c2e9ec>] (_raw_spin_unlock_irqrestore+0x34/0x44)
[ 36.102122] [<c0c2e9ec>] (_raw_spin_unlock_irqrestore) from [<c072e32c>] (regmap_read+0x4c/0x5c)
[ 36.110938] [<c072e32c>] (regmap_read) from [<c085d0f4>] (rtc_write_sync_lp+0x6c/0x98)
[ 36.118881] [<c085d0f4>] (rtc_write_sync_lp) from [<c085d160>] (snvs_rtc_alarm_irq_enable+0x40/0x4c)
[ 36.128041] [<c085d160>] (snvs_rtc_alarm_irq_enable) from [<c08567b4>] (rtc_timer_do_work+0xd8/0x1a8)
[ 36.137291] [<c08567b4>] (rtc_timer_do_work) from [<c01441b8>] (process_one_work+0x28c/0x76c)
[ 36.145840] [<c01441b8>] (process_one_work) from [<c01446cc>] (worker_thread+0x34/0x58c)
[ 36.153961] [<c01446cc>] (worker_thread) from [<c014aee4>] (kthread+0x138/0x150)
[ 36.161388] [<c014aee4>] (kthread) from [<c0107e14>] (ret_from_fork+0x14/0x20)
[ 36.168635] rcu_sched kthread starved for 2602 jiffies! g496 c495 f0x2 RCU_GP_WAIT_FQS(3) ->state=0x0 ->cpu=0
[ 36.178564] rcu_sched R running task 0 8 2 0x00000000
[ 36.185664] [<c0c288b0>] (__schedule) from [<c0c29134>] (schedule+0x3c/0xa0)
[ 36.192739] [<c0c29134>] (schedule) from [<c0c2db80>] (schedule_timeout+0x78/0x4e0)
[ 36.200422] [<c0c2db80>] (schedule_timeout) from [<c01a7ab0>] (rcu_gp_kthread+0x648/0x1864)
[ 36.208800] [<c01a7ab0>] (rcu_gp_kthread) from [<c014aee4>] (kthread+0x138/0x150)
[ 36.216309] [<c014aee4>] (kthread) from [<c0107e14>] (ret_from_fork+0x14/0x20)

This patch fixes by parsing the result of rtc_write_sync_lp() and
propagating both in the probe and elsewhere. If the RTC doesn't start we
don't proceed loading the driver and don't get into this loop mess later
on.

Fixes: 179a502f8c46 ("rtc: snvs: add Freescale rtc-snvs driver")
Signed-off-by: Bryan O'Donoghue <pure.logic@nexus-software.ie>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>

rtc: snvs: fix an incorrect check of return value

Function devm_regmap_init_mmio() returns an ERR_PTR on error. However,
in function snvs_rtc_probe() its return value is checked against NULL.
This patch fixes it by checking the return value with IS_ERR().

Signed-off-by: Pan Bian <bianpan2016@163.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

rtc: snvs: add a missing write sync

The clear of the LPTA_EN flag should be synced before writing to the
alarm register. Omitting this synchronization creates a race when
trying to change existing alarm.

Signed-off-by: Guy Shapiro <guy.shapiro@mobi-wize.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

rtc: snvs: return error in case enable_irq_wake fails

If enable_irq_wake fails, we should return that error code so that
entering suspend fails. Otherwise we will get a WARNING along with
the hint of a unbalanced wake disable:
Unbalanced IRQ 37 wake disable

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

rtc: snvs: use syscon to access register

snvs included rtc, on/off key, power-off module
change to syscon to access register

Signed-off-by: Frank Li <Frank.Li@freescale.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

rtc: snvs: fix wakealarm by call enable_irq_wake earlier

When entering suspend while an wakeup alarm is set, enable_set_wake
should make sure that the RTC interrupt keep being enabled and the
.irq_set_wake for the RTC interrupt get called. However, since the
driver uses the suspend_noirq callback, the call to enable_irq_wake
has been made after disabling the interrupts. While .irq_set_wake
has been called properly, the interrupt remained disabled.

Use the suspend callback to call enable_irq_wake early enough to
ensure the RTC interrupt remains enabled.

Fixes: 7654e9d4fd8f ("drivers/rtc/rtc-snvs: fix suspend/resume")
Cc: <stable@vger.kernel.org> # 3.19
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

rtc: snvs: fix build with CONFIG_PM_SLEEP disabled

Commit 7654e9d4fd8f ("drivers/rtc/rtc-snvs: fix suspend/resume")
replaces SIMPLE_DEV_PM_OPS with direct declaration of snvs_rtc_pm_ops,
but does so outside #ifdef CONFIG_PM_SLEEP. This causes the driver
build to fail if CONFIG_PM_SLEEP is not configured.

Fixes: 7654e9d4fd8f ("drivers/rtc/rtc-snvs: fix suspend/resume")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Cc: Sanchayan Maity <maitysanchayan@gmail.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-snvs: fix suspend/resume

The alarm interrupt handler also reads registers which are part of SNVS
and need clocks enabled. However, the resume function is called after
IRQ's have been enabled, hence this leads to a abort:

Unhandled fault: external abort on non-linefetch (0x1008) at 0x908c604c
Internal error: : 1008 [#1] ARM
Modules linked in:
CPU: 0 PID: 421 Comm: sh Not tainted 3.18.0-rc5-00135-g0689c67-dirty #1592
task: 8e03e800 ti: 8cad8000 task.ti: 8cad8000
PC is at snvs_rtc_irq_handler+0x14/0x74
LR is at handle_irq_event_percpu+0x3c/0x144

Fix this by using the .{suspend/resume}_noirq callbacks instead of
.{suspend/resume} .

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-snvs: add clock support

Add clock enable and disable support for the SNVS peripheral, which is
required for using the RTC within the SNVS block.

The clock is not strictly enforced, as this would break the i.MX devices.
The clocking for the i.MX devices seems to be enabled elsewhere and
enabling RTC SNVS for Vybrid results in a crash. This patch adds the
clock support but also makes it optional so Vybrid platform can use the
clock if defined while making sure not to break i.MX.

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>
Cc: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Stefan Agner <stefan@agner.ch>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

rtc: drop owner assignment from platform_drivers

A platform_driver does not need to set an owner, it will be populated by the
driver core.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/rtc/rtc-snvs.c: remove redundant of_match_ptr

The data structure of_match_ptr() protects is always compiled in.
Hence of_match_ptr() is not needed.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc/rtc-snvs.c: remove empty function

After the switch to devm_* functions and the removal of
rtc_device_unregister(), the 'remove' function does not do anything.
Delete it.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

rtc: rtc-snvs: use devm_rtc_device_register()

devm_rtc_device_register() is device managed and makes cleanup
paths simpler.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/rtc: use of_match_ptr() macro

This eliminates having an #ifdef returning NULL for the case when OF is
disabled. Maintains consistency in cases where OF is always selected.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

rtc: Convert to devm_ioremap_resource()

Convert all uses of devm_request_and_ioremap() to the newly introduced
devm_ioremap_resource() which provides more consistent error handling.

devm_ioremap_resource() provides its own error messages so all explicit
error messages can be removed from the failure code paths.

Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Drivers: rtc: remove __dev* attributes.

CONFIG_HOTPLUG is going away as an option. As a result, the __dev*
markings need to be removed.

This change removes the use of __devinit, __devexit_p, __devinitdata,
__devinitconst, and __devexit from these drivers.

Based on patches originally written by Bill Pemberton, but redone by me
in order to handle some of the coding style issues better, by hand.

Cc: Bill Pemberton <wfp5p@virginia.edu>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: Mike Frysinger <vapier.adi@gmail.com>
Cc: Wan ZongShun <mcuos.com@gmail.com>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

rtc: snvs: add Freescale rtc-snvs driver

Add an RTC driver for Freescale Secure Non-Volatile Storage (SNVS)
Low Power (LP) RTC.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Cc: Kim Phillips <kim.phillips@freescale.com>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>