kernel/linux.git/include/linux/mc146818rtc.h, branch v6.18.21

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: mc146818-lib: Fix the AltCentury for AMD platforms

2022-03-29T20:45:31+00:00

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 signedness bug in mc146818_get_time()

2022-01-16T22:34:43+00:00

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: extract mc146818_avoid_UIP

2021-12-16T20:50:06+00:00

Function mc146818_get_time() contains an elaborate mechanism of reading the RTC time while no RTC update is in progress. It turns out that reading the RTC alarm clock also requires avoiding the RTC update. Therefore, the mechanism in mc146818_get_time() should be reused - so extract it into a separate function. The logic in mc146818_avoid_UIP() is same as in mc146818_get_time() except that after every if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP) { there is now "mdelay(1)". To avoid producing a very unreadable patch, mc146818_get_time() will be refactored to use mc146818_avoid_UIP() in the next patch. Signed-off-by: Mateusz Jończyk Cc: Alessandro Zummo Cc: Alexandre Belloni Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20211210200131.153887-6-mat.jonczyk@o2.pl

rtc: mc146818-lib: fix RTC presence check

2021-12-16T20:50:06+00:00

To prevent an infinite loop in mc146818_get_time(), commit 211e5db19d15 ("rtc: mc146818: Detect and handle broken RTCs") added a check for RTC availability. Together with a later fix, it checked if bit 6 in register 0x0d is cleared. This, however, caused a false negative on a motherboard with an AMD SB710 southbridge; according to the specification [1], bit 6 of register 0x0d of this chipset is a scratchbit. This caused a regression in Linux 5.11 - the RTC was determined broken by the kernel and not used by rtc-cmos.c [3]. This problem was also reported in Fedora [4]. As a better alternative, check whether the UIP ("Update-in-progress") bit is set for longer then 10ms. If that is the case, then apparently the RTC is either absent (and all register reads return 0xff) or broken. Also limit the number of loop iterations in mc146818_get_time() to 10 to prevent an infinite loop there. The functions mc146818_get_time() and mc146818_does_rtc_work() will be refactored later in this patch series, in order to fix a separate problem with reading / setting the RTC alarm time. This is done so to avoid a confusion about what is being fixed when. In a previous approach to this problem, I implemented a check whether the RTC_HOURS register contains a value <= 24. This, however, sometimes did not work correctly on my Intel Kaby Lake laptop. According to Intel's documentation [2], "the time and date RAM locations (0-9) are disconnected from the external bus" during the update cycle so reading this register without checking the UIP bit is incorrect. [1] AMD SB700/710/750 Register Reference Guide, page 308, https://developer.amd.com/wordpress/media/2012/10/43009_sb7xx_rrg_pub_1.00.pdf [2] 7th Generation Intel ® Processor Family I/O for U/Y Platforms [...] Datasheet Volume 1 of 2, page 209 Intel's Document Number: 334658-006, https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/7th-and-8th-gen-core-family-mobile-u-y-processor-lines-i-o-datasheet-vol-1.pdf [3] Functions in arch/x86/kernel/rtc.c apparently were using it. [4] https://bugzilla.redhat.com/show_bug.cgi?id=1936688 Fixes: 211e5db19d15 ("rtc: mc146818: Detect and handle broken RTCs") Fixes: ebb22a059436 ("rtc: mc146818: Dont test for bit 0-5 in Register D") Signed-off-by: Mateusz Jończyk Cc: Thomas Gleixner Cc: Alessandro Zummo Cc: Alexandre Belloni Signed-off-by: Alexandre Belloni Link: https://lore.kernel.org/r/20211210200131.153887-5-mat.jonczyk@o2.pl

timekeeping: Ignore the bogus sleep time if pm_trace is enabled

2016-11-29T17:02:58+00:00

Power management suspend/resume tracing (ab)uses the RTC to store suspend/resume information persistently. As a consequence the RTC value is clobbered when timekeeping is resumed and tries to inject the sleep time. Commit a4f8f6667f09 ("timekeeping: Cap array access in timekeeping_debug") plugged a out of bounds array access in the timekeeping debug code which was caused by the clobbered RTC value, but we still use the clobbered RTC value for sleep time injection into kernel timekeeping, which will result in random adjustments depending on the stored "hash" value. To prevent this keep track of the RTC clobbering and ignore the invalid RTC timestamp at resume. If the system resumed successfully clear the flag, which marks the RTC as unusable, warn the user about the RTC clobber and recommend to adjust the RTC with 'ntpdate' or 'rdate'. [jstultz: Fixed up pr_warn formating, and implemented suggestions from Ingo] [ tglx: Rewrote changelog ] Originally-from: Thomas Gleixner Signed-off-by: Chen Yu Signed-off-by: John Stultz Acked-by: Pavel Machek Acked-by: Thomas Gleixner Cc: Prarit Bhargava Cc: "Rafael J. Wysocki" Cc: Richard Cochran Cc: Xunlei Pang Cc: Len Brown Link: http://lkml.kernel.org/r/1480372524-15181-3-git-send-email-john.stultz@linaro.org Signed-off-by: Thomas Gleixner

rtc: move mc146818 helper functions out-of-line

2016-06-25T23:20:08+00:00

The mc146818_get_time/mc146818_set_time functions are rather large inline functions in a global header file and are used in several drivers and in x86 specific code. Here we move them into a separate .c file that is compiled whenever any of the users require it. This also lets us remove the linux/acpi.h header inclusion from mc146818rtc.h, which in turn avoids some warnings about duplicate definition of the TRUE/FALSE macros. Signed-off-by: Arnd Bergmann Signed-off-by: Alexandre Belloni

rtc: cmos: move mc146818rtc code out of asm-generic/rtc.h

2016-06-03T22:20:00+00:00

Drivers should not really include stuff from asm-generic directly, and the PC-style cmos rtc driver does this in order to reuse the mc146818 implementation of get_rtc_time/set_rtc_time rather than the architecture specific one for the architecture it gets built for. To make it more obvious what is going on, this moves and renames the two functions into include/linux/mc146818rtc.h, which holds the other mc146818 specific code. Ideally it would be in a .c file, but that would require extra infrastructure as the functions are called by multiple drivers with conflicting dependencies. With this change, the asm-generic/rtc.h header also becomes much more generic, so it can be reused more easily across any architecture that still relies on the genrtc driver. The only caller of the internal __get_rtc_time/__set_rtc_time functions is in arch/alpha/kernel/rtc.c, and we just change those over to the new naming. Signed-off-by: Arnd Bergmann Acked-by: Geert Uytterhoeven Signed-off-by: Alexandre Belloni

drivers/rtc/rtc-cmos.c: drivers/char/rtc.c features for DECstation support

2014-06-06T23:08:07+00:00

This brings in drivers/char/rtc.c functionality required for DECstation and, should the maintainers decide to switch, Alpha systems to use rtc-cmos. Specifically these features are made available: * RTC iomem rather than x86/PCI port I/O mapping, controlled with the RTC_IOMAPPED macro as with the original driver. The DS1287A chip in all DECstation systems is mapped in the host bus address space as a contiguous block of 64 32-bit words of which the least significant byte accesses the RTC chip for both reads and writes. All the address and data window register accesses are made transparently by the chipset glue logic so that the device appears directly mapped on the host bus. * A way to set the size of the address space explicitly with the newly-added `address_space' member of the platform part of the RTC device structure. This avoids the unreliable heuristics that does not work in a setup where the RTC is not explicitly accessed with the usual address and data window register pair. * The ability to use the RTC periodic interrupt as a system clock device, which is implemented by arch/mips/kernel/cevt-ds1287.c for DECstation systems and takes the RTC interrupt away from the RTC driver. Eventually hooking back to the clock device's interrupt handler should be possible for the purpose of the alarm clock and possibly also update-in-progress interrupt, but this is not done by this change. o To avoid interfering with the clock interrupt all the places where the RTC interrupt mask is fiddled with are only executed if and IRQ has been assigned to the RTC driver. o To avoid changing the clock setup Register A is not fiddled with if CMOS_RTC_FLAGS_NOFREQ is set in the newly-added `flags' member of the platform part of the RTC device structure. Originally, in drivers/char/rtc.c, this was keyed with the absence of the RTC interrupt, just like the interrupt mask, but there only the periodic interrupt frequency is set, whereas rtc-cmos also sets the divider bits. Therefore a new flag is introduced so that systems where the RTC interrupt is not usable rather than used as a system clock device can fully initialise the RTC. * A small clean-up is made to the IRQ assignment code that makes the IRQ number hardcoded to -1 rather than arbitrary -ENXIO (or whatever error happens to be returned by platform_get_irq) where no IRQ has been assigned to the RTC driver (NO_IRQ might be another candidate, but it looks like this macro has inconsistent or missing definitions and limited use and might therefore be unsafe). Verified to work correctly with a DECstation 5000/240 system. [akpm@linux-foundation.org: fix weird code layout] Signed-off-by: Maciej W. Rozycki Cc: Alessandro Zummo Cc: Ralf Baechle Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

rtc: fall back to requesting only the ports we actually use

2007-11-15T02:45:41+00:00

Firmware like PNPBIOS or ACPI can report the address space consumed by the RTC. The actual space consumed may be less than the size (RTC_IO_EXTENT) assumed by the RTC driver. The PNP core doesn't request resources yet, but I'd like to make it do so. If/when it does, the RTC_IO_EXTENT request may fail, which prevents the RTC driver from loading. Since we only use the RTC index and data registers at RTC_PORT(0) and RTC_PORT(1), we can fall back to requesting just enough space for those. If the PNP core requests resources, this results in typical I/O port usage like this: 0070-0073 : 00:06 <-- PNP device 00:06 responds to 70-73 0070-0071 : rtc <-- RTC driver uses only 70-71 instead of the current: 0070-0077 : rtc <-- RTC_IO_EXTENT == 8 Signed-off-by: Bjorn Helgaas Cc: Alessandro Zummo Cc: David Brownell Cc: Ralf Baechle Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds