kernel/drivers/rtc/rtc-mc146818-lib.c, branch linux-6.9.y

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

2023-12-17T21:33:55Z

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

2023-12-17T21:33:55Z

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: mc146818-lib: Adjust failure return code for mc146818_get_time()

2023-12-17T21:33:54Z

mc146818_get_time() calls mc146818_avoid_UIP() to avoid fetching the time while RTC update is in progress (UIP). When this fails, the return code is -EIO, but actually there was no IO failure. The reason for the return from mc146818_avoid_UIP() is that the UIP wasn't cleared in the time period. Adjust the return code to -ETIMEDOUT to match the behavior. Tested-by: Mateusz Jończyk Reviewed-by: Mateusz Jończyk Acked-by: Mateusz Jończyk Cc: Fixes: 2a61b0ac5493 ("rtc: mc146818-lib: refactor mc146818_get_time") Signed-off-by: Mario Limonciello Link: https://lore.kernel.org/r/20231128053653.101798-2-mario.limonciello@amd.com Signed-off-by: Alexandre Belloni

rtc: mc146818-lib: reduce RTC_UIP polling period

2022-06-24T19:23:50Z

Waiting 1ms every time is not necessary, for example on some AMD boxes the RTC_UIP bit is documented as being high for around 270 microseconds in some cases [1], which agreed with experiments on an SB710 southbridge. So 100us seems optimal. This in preparation for mach_get_cmos_time() refactoring. The functions mc146818_get_time() and mach_get_cmos_time() in arch/x86/kernel/rtc.c perform the same function and the code is duplicated. mach_get_cmos_time() is busy waiting for the RTC_UIP bit to clear, so make mc146818_get_time() more similar to it by reducing the polling period. [1] AMD SB700/710/750 Register Reference Guide, page 307, https://developer.amd.com/wordpress/media/2012/10/43009_sb7xx_rrg_pub_1.00.pdf "SB700 A12: The UIP high pulse is 270 μS Typical when SS on SRC clock is OFF and 100μ min when SRC SS is ON." [sic] Signed-off-by: Mateusz Jończyk Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Borislav Petkov Cc: Dave Hansen Cc: x86@kernel.org Cc: "H. Peter Anvin" Cc: Alessandro Zummo Cc: Alexandre Belloni Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20220225215011.861477-2-mat.jonczyk@o2.pl

rtc: mc146818-lib: Fix the AltCentury for AMD platforms

2022-03-29T20:45:31Z

Setting the century forward has been failing on AMD platforms. There was a previous attempt at fixing this for family 0x17 as part of commit 7ad295d5196a ("rtc: Fix the AltCentury value on AMD/Hygon platform") but this was later reverted due to some problems reported that appeared to stem from an FW bug on a family 0x17 desktop system. The same comments mentioned in the previous commit continue to apply to the newer platforms as well. ``` MC146818 driver use function mc146818_set_time() to set register RTC_FREQ_SELECT(RTC_REG_A)'s bit4-bit6 field which means divider stage reset value on Intel platform to 0x7. While AMD/Hygon RTC_REG_A(0Ah)'s bit4 is defined as DV0 [Reference]: DV0 = 0 selects Bank 0, DV0 = 1 selects Bank 1. Bit5-bit6 is defined as reserved. DV0 is set to 1, it will select Bank 1, which will disable AltCentury register(0x32) access. As UEFI pass acpi_gbl_FADT.century 0x32 (AltCentury), the CMOS write will be failed on code: CMOS_WRITE(century, acpi_gbl_FADT.century). Correct RTC_REG_A bank select bit(DV0) to 0 on AMD/Hygon CPUs, it will enable AltCentury(0x32) register writing and finally setup century as expected. ``` However in closer examination the change previously submitted was also modifying bits 5 & 6 which are declared reserved in the AMD documentation. So instead modify just the DV0 bank selection bit. Being cognizant that there was a failure reported before, split the code change out to a static function that can also be used for exclusions if any regressions such as Mikhail's pop up again. Cc: Jinke Fan Cc: Mikhail Gavrilov Link: https://lore.kernel.org/all/CABXGCsMLob0DC25JS8wwAYydnDoHBSoMh2_YLPfqm3TTvDE-Zw@mail.gmail.com/ Link: https://www.amd.com/system/files/TechDocs/51192_Bolton_FCH_RRG.pdf Signed-off-by: Raul E Rangel Signed-off-by: Mario Limonciello Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20220111225750.1699-1-mario.limonciello@amd.com

rtc: mc146818-lib: fix locking in mc146818_set_time

2022-03-23T18:58:37Z

In mc146818_set_time(), CMOS_READ(RTC_CONTROL) was performed without the rtc_lock taken, which is required for CMOS accesses. Fix this. Nothing in kernel modifies RTC_DM_BINARY, so a separate critical section is allowed here. Fixes: dcf257e92622 ("rtc: mc146818: Reduce spinlock section in mc146818_set_time()") Signed-off-by: Mateusz Jończyk Cc: Alessandro Zummo Cc: Alexandre Belloni Cc: Thomas Gleixner Cc: stable@vger.kernel.org Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20220220090403.153928-1-mat.jonczyk@o2.pl

rtc: cmos: Evaluate century appropriate

2022-01-16T22:50:26Z

There's limiting the year to 2069. When setting the rtc year to 2070, reading it returns 1970. Evaluate century starting from 19 to count the correct year. $ sudo date -s 20700106 Mon 06 Jan 2070 12:00:00 AM CST $ sudo hwclock -w $ sudo hwclock -r 1970-01-06 12:00:49.604968+08:00 Fixes: 2a4daadd4d3e5071 ("rtc: cmos: ignore bogus century byte") Signed-off-by: Riwen Lu Acked-by: Eric Wong Reviewed-by: Mateusz Jończyk Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20220106084609.1223688-1-luriwen@kylinos.cn

rtc: mc146818-lib: fix signedness bug in mc146818_get_time()

2022-01-16T22:34:43Z

The mc146818_get_time() function returns zero on success or negative a error code on failure. It needs to be type int. Fixes: d35786b3a28d ("rtc: mc146818-lib: change return values of mc146818_get_time()") Signed-off-by: Dan Carpenter Reviewed-by: Mateusz Jończyk Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20220111071922.GE11243@kili

rtc: mc146818-lib: refactor mc146818_does_rtc_work

2021-12-16T20:50:06Z

Refactor mc146818_does_rtc_work() so that it uses mc146818_avoid_UIP(). It is enough to call mc146818_avoid_UIP() with no callback. Signed-off-by: Mateusz Jończyk Cc: Alessandro Zummo Cc: Alexandre Belloni Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20211210200131.153887-8-mat.jonczyk@o2.pl

rtc: mc146818-lib: refactor mc146818_get_time

2021-12-16T20:50:06Z

Refactor mc146818_get_time() so that it uses mc146818_avoid_UIP(). Signed-off-by: Mateusz Jończyk Cc: Alessandro Zummo Cc: Alexandre Belloni Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20211210200131.153887-7-mat.jonczyk@o2.pl