linux-stable.git/drivers/rtc/rtc-ds1307.c, branch linux-rolling-stable

rtc: ds1307: Fix off-by-one issue with wday for rx8130

2026-07-24T14:20:29+00:00

[ Upstream commit 6882aab3c66112b33b251be95c09c8ead3e8d580 ]

The RTC represent each weekday with a individual bit set in the WDAY
register, where the 0th bit represent the first day of the week and the
6th bit represents the last day of the week. For each passed day the
chip performs a rotary-left-shift by one to advance the weekday by one.

The tm_wday field represent weekdays by a value in the range of 0-6.

The fls() function return the bit index of the last bit set. To handle
when there are no bits set it will return 0, and if the 0th bit is set
it will return 1, and if the 1st bit is set it will return 2, and so on.

In order to make the result of the fls() function fall into the expected
range of 0-6 (instead of 1-7) this patch subtracts one from the result
(which matches how the value is written in ds1307_set_time()).

Fixes: 204756f016726 ("rtc: ds1307: Fix wday settings for rx8130")
Reviewed-by: Nobuhiro Iwamatsu 
Signed-off-by: Fredrik M Olsson 
Link: https://patch.msgid.link/20260520-ds1307-rx8901-add-v2-2-e069ea32e1db@axis.com
Signed-off-by: Alexandre Belloni 
Signed-off-by: Sasha Levin

rtc: ds1307: handle oscillator stop flag for ds1337/ds1339/ds3231

2026-07-24T14:20:23+00:00

[ Upstream commit a091e1ba3b68cabc9caedafc6f81d9fe9b3b2200 ]

Prior to commit 48458654659c ("rtc: ds1307: remove clear of oscillator
stop flag (OSF) in probe"), the oscillator stop flag (OSF) bit was
checked during device probe for the ds1337, ds1339, ds1341, and ds3231
chips; if it was set, it would be cleared and a warning would be logged
saying "SET TIME!". Since that commit, the OSF bit is no longer cleared,
but the warning is still printed.

Directly following that commit, there was no way to get rid of this
warning because nothing cleared the OSF bit on these chips.

The commit associated with the previous commit, 523923cfd5d6 ("rtc:
ds1307: handle oscillator stop flag (OSF) for ds1341"), made proper use
of the OSF when getting and setting the time in the RTC. However, the
other RTC variants ds1337, ds1339 and ds3231 didn't have a corresponding
change made.

Given that the OSF bit is no longer cleared at probe time when it is
set, the remaining three chips should have the same handling as the
ds1341 chip has for the OSF bit.

Fix the issue on the ds1337, ds1339 and ds3231 chips by applying the
same logic as the ds1341 has to these chips.

Note that any devices brought up between the first referenced commit and
this one may begin mistrusting the time reported by the RTC until it is
set again, if the bit was never explicitly cleared.

Note that only the ds1339 was tested with this change, but the
datasheets for the other chips contain essentially identical
descriptions of the OSF bit so the same change should work.

Signed-off-by: Ronan Dalton 
Cc: linux-rtc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: Alexandre Belloni 
Cc: Tyler Hicks 
Cc: Sasha Levin 
Cc: Meagan Lloyd 
Cc: Rodolfo Giometti 
Cc: Chris Packham 
Fixes: 48458654659c ("rtc: ds1307: remove clear of oscillator stop flag (OSF) in probe")
Reviewed-by: Meagan Lloyd 
Reviewed-by: Tyler Hicks 
Link: https://patch.msgid.link/20260508032518.3696705-2-ronan.dalton@alliedtelesis.co.nz
Signed-off-by: Alexandre Belloni 
Signed-off-by: Sasha Levin

rtc: ds1307: convert from round_rate() to determine_rate()

2025-08-03T00:57:05+00:00

The round_rate() clk ops is deprecated, so migrate this driver from
round_rate() to determine_rate() using the Coccinelle semantic patch
on the cover letter of this series.

Signed-off-by: Brian Masney 
Link: https://lore.kernel.org/r/20250710-rtc-clk-round-rate-v1-7-33140bb2278e@redhat.com
Signed-off-by: Alexandre Belloni

rtc: ds1307: fix incorrect maximum clock rate handling

2025-08-03T00:57:05+00:00

When ds3231_clk_sqw_round_rate() is called with a requested rate higher
than the highest supported rate, it currently returns 0, which disables
the clock. According to the clk API, round_rate() should instead return
the highest supported rate. Update the function to return the maximum
supported rate in this case.

Fixes: 6c6ff145b3346 ("rtc: ds1307: add clock provider support for DS3231")
Signed-off-by: Brian Masney 
Link: https://lore.kernel.org/r/20250710-rtc-clk-round-rate-v1-1-33140bb2278e@redhat.com
Signed-off-by: Alexandre Belloni

rtc: ds1307: handle oscillator stop flag (OSF) for ds1341

2025-07-23T21:24:38+00:00

In using CONFIG_RTC_HCTOSYS, rtc_hctosys() will sync the RTC time to the
kernel time as long as rtc_read_time() succeeds. In some power loss
situations, our supercapacitor-backed DS1342 RTC comes up with either an
unpredictable future time or the default 01/01/00 from the datasheet.
The oscillator stop flag (OSF) is set in these scenarios due to the
power loss and can be used to determine the validity of the RTC data.

This change expands the oscillator stop flag (OSF) handling that has
already been implemented for some chips to the ds1341 chip (DS1341 and
DS1342 share a datasheet). This handling manages the validity of the RTC
data in .read_time and .set_time based on the OSF.

Signed-off-by: Meagan Lloyd 
Reviewed-by: Tyler Hicks 
Acked-by: Rodolfo Giometti 
Link: https://lore.kernel.org/r/1749665656-30108-3-git-send-email-meaganlloyd@linux.microsoft.com
Signed-off-by: Alexandre Belloni

rtc: ds1307: remove clear of oscillator stop flag (OSF) in probe

2025-07-23T21:24:38+00:00

In using CONFIG_RTC_HCTOSYS, rtc_hctosys() will sync the RTC time to the
kernel time as long as rtc_read_time() succeeds. In some power loss
situations, our supercapacitor-backed DS1342 RTC comes up with either an
unpredictable future time or the default 01/01/00 from the datasheet.
The oscillator stop flag (OSF) is set in these scenarios due to the
power loss and can be used to determine the validity of the RTC data.

Some chip types in the ds1307 driver already have OSF handling to
determine whether .read_time provides valid RTC data or returns -EINVAL.

This change removes the clear of the OSF in .probe as the OSF needs to
be preserved to expand the OSF handling to the ds1341 chip type (note
that DS1341 and DS1342 share a datasheet).

Signed-off-by: Meagan Lloyd 
Reviewed-by: Tyler Hicks 
Acked-by: Rodolfo Giometti 
Link: https://lore.kernel.org/r/1749665656-30108-2-git-send-email-meaganlloyd@linux.microsoft.com
Signed-off-by: Alexandre Belloni

rtc: ds1307: stop disabling alarms on probe

2025-03-06T21:12:14+00:00

It is a bad practice to disable alarms on probe or remove as this will
prevent alarms across reboots.

Link: https://lore.kernel.org/r/20250303223744.1135672-1-alexandre.belloni@bootlin.com
Signed-off-by: Alexandre Belloni

rtc: ds1307: Clamp year to valid BCD (0-99) in `set_time()`

2024-07-06T22:39:27+00:00

`tm_year` may go up to 299 if the device supports the
century bit. Therefore, subtracting may not give us
a valid 2-digit number, but modulo does.

Co-developed-by: Szentendrei, Tamás 
Signed-off-by: Szentendrei, Tamás 
Signed-off-by: Csókás, Bence 
Link: https://lore.kernel.org/r/20240611072411.671600-2-csokas.bence@prolan.hu
Signed-off-by: Alexandre Belloni

rtc: ds1307: Detect oscillator fail on mcp794xx

2024-07-06T22:39:15+00:00

This patch enables the detection of the oscillator failure on mcp794xx chips.

Co-developed-by: Szentendrei, Tamás 
Signed-off-by: Szentendrei, Tamás 
Signed-off-by: Csókás, Bence 
Link: https://lore.kernel.org/r/20240611072411.671600-1-csokas.bence@prolan.hu
Signed-off-by: Alexandre Belloni

rtc: ds1307: fix Wvoid-pointer-to-enum-cast warning

2023-08-15T23:32:08+00:00

'type' is an enum, thus cast of pointer on 64-bit compile test with W=1
causes:

  rtc-ds1307.c:1747:18: error: cast to smaller integer type 'enum ds_type' from 'const void *' [-Werror,-Wvoid-pointer-to-enum-cast]

Signed-off-by: Krzysztof Kozlowski 
Link: https://lore.kernel.org/r/20230810103902.151145-1-krzysztof.kozlowski@linaro.org
Signed-off-by: Alexandre Belloni