kernel/linux.git/drivers/rtc/rtc-cmos.c, branch v6.12.80

rtc: cmos: use spin_lock_irqsave in cmos_interrupt

2025-07-10T14:04:41+00:00

commit 00a39d8652ff9088de07a6fe6e9e1893452fe0dd upstream. cmos_interrupt() can be called in a non-interrupt context, such as in an ACPI event handler (which runs in an interrupt thread). Therefore, usage of spin_lock(&rtc_lock) is insecure. Use spin_lock_irqsave() / spin_unlock_irqrestore() instead. Before a misguided commit 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ") the cmos_interrupt() function used spin_lock_irqsave(). That commit changed it to spin_lock() and broke locking, which was partially fixed in commit 13be2efc390a ("rtc: cmos: Disable irq around direct invocation of cmos_interrupt()") That second commit did not take account of the ACPI fixed event handler pathway, however. It introduced local_irq_disable() workarounds in cmos_check_wkalrm(), which can cause problems on PREEMPT_RT kernels and are now unnecessary. Add an explicit comment so that this change will not be reverted by mistake. Cc: stable@vger.kernel.org Fixes: 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ") Signed-off-by: Mateusz Jończyk Reviewed-by: Sebastian Andrzej Siewior Tested-by: Chris Bainbridge Reported-by: Chris Bainbridge Closes: https://lore.kernel.org/all/aDtJ92foPUYmGheF@debian.local/ Link: https://lore.kernel.org/r/20250607210608.14835-1-mat.jonczyk@o2.pl Signed-off-by: Alexandre Belloni Signed-off-by: Greg Kroah-Hartman

rtc: cmos: avoid taking rtc_lock for extended period of time

2024-12-14T19:04:09+00:00

[ Upstream commit 0a6efab33eab4e973db26d9f90c3e97a7a82e399 ] On my device reading entirety of /sys/devices/pnp0/00:03/cmos_nvram0/nvmem takes about 9 msec during which time interrupts are off on the CPU that does the read and the thread that performs the read can not be migrated or preempted by another higher priority thread (RT or not). Allow readers and writers be preempted by taking and releasing rtc_lock spinlock for each individual byte read or written rather than once per read/write request. Signed-off-by: Dmitry Torokhov Reviewed-by: Mateusz Jończyk Link: https://lore.kernel.org/r/Zxv8QWR21AV4ztC5@google.com Signed-off-by: Alexandre Belloni Signed-off-by: Sasha Levin

rtc: cmos: Fix return value of nvmem callbacks

2024-06-27T22:21:06+00:00

Read/write callbacks registered with nvmem core expect 0 to be returned on success and a negative value to be returned on failure. cmos_nvram_read()/cmos_nvram_write() currently return the number of bytes read or written, fix to return 0 on success and -EIO incase number of bytes requested was not read or written. Fixes: 8b5b7958fd1c ("rtc: cmos: use generic nvmem") Cc: stable@vger.kernel.org Signed-off-by: Joy Chakraborty Reviewed-by: Dan Carpenter Link: https://lore.kernel.org/r/20240612083635.1253039-1-joychakr@google.com Signed-off-by: Alexandre Belloni

rtc: Extend timeout for waiting for UIP to clear to 1s

2023-12-17T21:33:55+00:00

Specs don't say anything about UIP being cleared within 10ms. They only say that UIP won't occur for another 244uS. If a long NMI occurs while UIP is still updating it might not be possible to get valid data in 10ms. This has been observed in the wild that around s2idle some calls can take up to 480ms before UIP is clear. Adjust callers from outside an interrupt context to wait for up to a 1s instead of 10ms. Cc: # 6.1.y Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP") Reported-by: Carsten Hatger Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217626 Tested-by: Mateusz Jończyk Reviewed-by: Mateusz Jończyk Acked-by: Mateusz Jończyk Signed-off-by: Mario Limonciello Link: https://lore.kernel.org/r/20231128053653.101798-5-mario.limonciello@amd.com Signed-off-by: Alexandre Belloni

rtc: Add support for configuring the UIP timeout for RTC reads

2023-12-17T21:33:55+00:00

The UIP timeout is hardcoded to 10ms for all RTC reads, but in some contexts this might not be enough time. Add a timeout parameter to mc146818_get_time() and mc146818_get_time_callback(). If UIP timeout is configured by caller to be >=100 ms and a call takes this long, log a warning. Make all callers use 10ms to ensure no functional changes. Cc: # 6.1.y Fixes: ec5895c0f2d8 ("rtc: mc146818-lib: extract mc146818_avoid_UIP") Signed-off-by: Mario Limonciello Tested-by: Mateusz Jończyk Reviewed-by: Mateusz Jończyk Acked-by: Mateusz Jończyk Link: https://lore.kernel.org/r/20231128053653.101798-4-mario.limonciello@amd.com Signed-off-by: Alexandre Belloni

rtc: Adjust failure return code for cmos_set_alarm()

2023-12-17T21:33:54+00:00

When mc146818_avoid_UIP() fails to return a valid value, this is because UIP didn't clear in the timeout period. Adjust the return code in this case to -ETIMEDOUT. Tested-by: Mateusz Jończyk Reviewed-by: Mateusz Jończyk Acked-by: Mateusz Jończyk Cc: Fixes: cdedc45c579f ("rtc: cmos: avoid UIP when reading alarm time") Fixes: cd17420ebea5 ("rtc: cmos: avoid UIP when writing alarm time") Signed-off-by: Mario Limonciello Link: https://lore.kernel.org/r/20231128053653.101798-3-mario.limonciello@amd.com Signed-off-by: Alexandre Belloni

rtc: cmos: Use ACPI alarm for non-Intel x86 systems too

2023-11-17T17:35:43+00:00

Intel systems > 2015 have been configured to use ACPI alarm instead of HPET to avoid s2idle issues. Having HPET programmed for wakeup causes problems on AMD systems with s2idle as well. One particular case is that the systemd "SuspendThenHibernate" feature doesn't work properly on the Framework 13" AMD model. Switching to using ACPI alarm fixes the issue. Adjust the quirk to apply to AMD/Hygon systems from 2021 onwards. This matches what has been tested and is specifically to avoid potential risk to older systems. Cc: # 6.1+ Reported-by: Reported-by: Closes: https://github.com/systemd/systemd/issues/24279 Reported-by: Kelvie Wong Closes: https://community.frame.work/t/systemd-suspend-then-hibernate-wakes-up-after-5-minutes/39392 Signed-off-by: Mario Limonciello Link: https://lore.kernel.org/r/20231106162310.85711-1-mario.limonciello@amd.com Signed-off-by: Alexandre Belloni

rtc: cmos: Report supported alarm limit to rtc infrastructure

2023-08-27T21:50:22+00:00

The alarm window supported by the cmos RTC depends on the chip and its configuration. Report the limit to the RTC core. Cc: Brian Norris Signed-off-by: Guenter Roeck Link: https://lore.kernel.org/r/20230817225537.4053865-5-linux@roeck-us.net Signed-off-by: Alexandre Belloni

rtc: cmos: Convert to platform remove callback returning void

2023-03-17T22:03:17+00:00

The .remove() callback for a platform driver returns an int which makes many driver authors wrongly assume it's possible to do error handling by returning an error code. However the value returned is (mostly) ignored and this typically results in resource leaks. To improve here there is a quest to make the remove callback return void. In the first step of this quest all drivers are converted to .remove_new() which already returns void. Trivially convert this driver from always returning zero in the remove callback to the void returning variant. Signed-off-by: Uwe Kleine-König Link: https://lore.kernel.org/r/20230304133028.2135435-10-u.kleine-koenig@pengutronix.de Signed-off-by: Alexandre Belloni

rtc: cmos: Disable ACPI RTC event on removal

2022-11-15T20:07:14+00:00

Make cmos_do_remove() drop the ACPI RTC fixed event handler so as to prevent it from operating on stale data in case the event triggers after driver removal. Fixes: 311ee9c151ad ("rtc: cmos: allow using ACPI for RTC alarm instead of HPET") Signed-off-by: Rafael J. Wysocki Reviewed-by: Zhang Rui Tested-by: Zhang Rui Reviewed-by: Andy Shevchenko Link: https://lore.kernel.org/r/2224609.iZASKD2KPV@kreacher Signed-off-by: Alexandre Belloni