Changes in i8253.c

94cff946 - clocksource/i8253: Use raw_spinlock_irqsave() in clockevent_i8253_disable()

Fri, 04 Apr 2025 13:31:16 +0000

clocksource/i8253: Use raw_spinlock_irqsave() in clockevent_i8253_disable()On x86 during boot, clockevent_i8253_disable() can be invoked viax86_late_time_init -> hpet_time_init() -> pit_timer_init() which happenswith enabled interrupts.If some of the old i8253 hardware is actually used then lockdep will noticethat i8253_lock is used in hard interrupt context. This causes lockdep tocomplain because it observed the lock being acquired with interruptsenabled and in hard interrupt context.Make clockevent_i8253_disable() acquire the lock withraw_spinlock_irqsave() to cure this.[ tglx: Massage change log and use guard() ]Fixes: c8c4076723dac ("x86/timer: Skip PIT initialization on modern chipsets")Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.orgLink: https://lore.kernel.org/all/20250404133116.p-XRWJXf@linutronix.de List of files: /linux-6.15/drivers/clocksource/i8253.c

531b2ca0 - clockevents/drivers/i8253: Fix stop sequence for timer 0

Fri, 02 Aug 2024 13:55:55 +0000

clockevents/drivers/i8253: Fix stop sequence for timer 0According to the data sheet, writing the MODE register should stop thecounter (and thus the interrupts). This appears to work on real hardware,at least modern Intel and AMD systems. It should also work on Hyper-V.However, on some buggy virtual machines the mode change doesn't have anyeffect until the counter is subsequently loaded (or perhaps when the IRQnext fires).So, set MODE 0 and then load the counter, to ensure that those buggy VMsdo the right thing and the interrupts stop. And then write MODE 0 *again*to stop the counter on compliant implementations too.Apparently, Hyper-V keeps firing the IRQ *repeatedly* even in mode zerowhen it should only happen once, but the second MODE write stops that too.Userspace test program (mostly written by tglx):===== #include #include #include #include #include static __always_inline void __out##bwl(type value, uint16_t port) \{ \ asm volatile("out" #bwl " %" #bw "0, %w1" \ : : "a"(value), "Nd"(port)); \} \ \static __always_inline type __in##bwl(uint16_t port) \{ \ type value; \ asm volatile("in" #bwl " %w1, %" #bw "0" \ : "=a"(value) : "Nd"(port)); \ return value; \}BUILDIO(b, b, uint8_t) #define inb __inb #define outb __outb #define PIT_MODE 0x43 #define PIT_CH0 0x40 #define PIT_CH2 0x42static int is8254;static void dump_pit(void){ if (is8254) { // Latch and output counter and status outb(0xC2, PIT_MODE); printf("%02x %02x %02x\n", inb(PIT_CH0), inb(PIT_CH0), inb(PIT_CH0)); } else { // Latch and output counter outb(0x0, PIT_MODE); printf("%02x %02x\n", inb(PIT_CH0), inb(PIT_CH0)); }}int main(int argc, char* argv[]){ int nr_counts = 2; if (argc > 1) nr_counts = atoi(argv[1]); if (argc > 2) is8254 = 1; if (ioperm(0x40, 4, 1) != 0) return 1; dump_pit(); printf("Set oneshot\n"); outb(0x38, PIT_MODE); outb(0x00, PIT_CH0); outb(0x0F, PIT_CH0); dump_pit(); usleep(1000); dump_pit(); printf("Set periodic\n"); outb(0x34, PIT_MODE); outb(0x00, PIT_CH0); outb(0x0F, PIT_CH0); dump_pit(); usleep(1000); dump_pit(); dump_pit(); usleep(100000); dump_pit(); usleep(100000); dump_pit(); printf("Set stop (%d counter writes)\n", nr_counts); outb(0x30, PIT_MODE); while (nr_counts--) outb(0xFF, PIT_CH0); dump_pit(); usleep(100000); dump_pit(); usleep(100000); dump_pit(); printf("Set MODE 0\n"); outb(0x30, PIT_MODE); dump_pit(); usleep(100000); dump_pit(); usleep(100000); dump_pit(); return 0;}=====Suggested-by: Sean Christopherson Co-developed-by: Li RongQing Signed-off-by: Li RongQing Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Tested-by: Michael Kelley Link: https://lore.kernel.org/all/20240802135555.564941-2-dwmw2@infradead.org List of files: /linux-6.15/drivers/clocksource/i8253.c

70e6b7d9 - x86/i8253: Disable PIT timer 0 when not in use

Fri, 02 Aug 2024 13:55:54 +0000

x86/i8253: Disable PIT timer 0 when not in useLeaving the PIT interrupt running can cause noticeable steal time forvirtual guests. The VMM generally has a timer which toggles the IRQ inputto the PIC and I/O APIC, which takes CPU time away from the guest. Evenon real hardware, running the counter may use power needlessly (albeitnot much).Make sure it's turned off if it isn't going to be used.Signed-off-by: David Woodhouse Signed-off-by: Thomas Gleixner Tested-by: Michael Kelley Link: https://lore.kernel.org/all/20240802135555.564941-1-dwmw2@infradead.org List of files: /linux-6.15/drivers/clocksource/i8253.c

35b69a42 - clockevents/drivers/i8253: Add support for PIT shutdown quirk

Sun, 04 Nov 2018 03:48:54 +0000

clockevents/drivers/i8253: Add support for PIT shutdown quirkAdd support for platforms where pit_shutdown() doesn't work because of aquirk in the PIT emulation. On these platforms setting the counter registerto zero causes the PIT to start running again, negating the shutdown.Provide a global variable that controls whether the counter register iszero'ed, which platform specific code can override.Signed-off-by: Michael Kelley Signed-off-by: Thomas Gleixner Cc: "gregkh@linuxfoundation.org" Cc: "devel@linuxdriverproject.org" Cc: "daniel.lezcano@linaro.org" Cc: "virtualization@lists.linux-foundation.org" Cc: "jgross@suse.com" Cc: "akataria@vmware.com" Cc: "olaf@aepfle.de" Cc: "apw@canonical.com" Cc: vkuznets Cc: "jasowang@redhat.com" Cc: "marcelo.cerri@canonical.com" Cc: KY Srinivasan Cc: stable@vger.kernel.orgLink: https://lkml.kernel.org/r/1541303219-11142-2-git-send-email-mikelley@microsoft.com List of files: /linux-6.15/drivers/clocksource/i8253.c

b2441318 - License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Wed, 01 Nov 2017 14:07:57 +0000

License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseMany source files in the tree are missing licensing information, whichmakes it harder for compliance tools to determine the correct license.By default all files without license information are under the defaultlicense of the kernel, which is GPL version 2.Update the files which contain no license information with the 'GPL-2.0'SPDX license identifier. The SPDX identifier is a legally bindingshorthand, which can be used instead of the full boiler plate text.This patch is based on work done by Thomas Gleixner and Kate Stewart andPhilippe Ombredanne.How this work was done:Patches were generated and checked against linux-4.14-rc6 for a subset ofthe use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information,Further patches will be generated in subsequent months to fix up caseswhere non-standard license headers were used, and references to licensehad to be inferred by heuristics based on keywords.The analysis to determine which SPDX License Identifier to be applied toa file was done in a spreadsheet of side by side results from of theoutput of two independent scanners (ScanCode & Windriver) producing SPDXtag:value files created by Philippe Ombredanne. Philippe prepared thebase worksheet, and did an initial spot review of a few 1000 files.The 4.13 kernel was the starting point of the analysis with 60,537 filesassessed. Kate Stewart did a file by file comparison of the scannerresults in the spreadsheet to determine which SPDX license identifier(s)to be applied to the file. She confirmed any determination that was notimmediately clear with lawyers working with the Linux Foundation.Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines).All documentation files were explicitly excluded.The following heuristics were used to determine which SPDX licenseidentifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time.In total, over 70 hours of logged manual review was done on thespreadsheet to determine the SPDX license identifiers to apply to thesource files by Kate, Philippe, Thomas and, in some cases, confirmationby lawyers working with the Linux Foundation.Kate also obtained a third independent scan of the 4.13 code base fromFOSSology, and compared selected files where the other two scannersdisagreed against that SPDX file, to see if there was new insights. TheWindriver scanner is based on an older version of FOSSology in part, sothey are related.Thomas did random spot checks in about 500 files from the spreadsheetsfor the uapi headers and agreed with SPDX license identifier in thefiles he inspected. For the non-uapi files Thomas did random spot checksin about 15000 files.In initial set of patches against 4.14-rc6, 3 files were found to havecopy/paste license identifier errors, and have been fixed to reflect thecorrect identifier.Additionally Philippe spent 10 hours this week doing a detailed manualinspection and review of the 12,461 patched files from the initial patchversion early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correctThis produced a worksheet with 20 files needing minor correction. Thisworksheet was then exported into 3 different .csv files for thedifferent types of files to be modified.These .csv files were then reviewed by Greg. Thomas wrote a script toparse the csv files and add the proper SPDX tag to the file, in theformat that the file expected. This script was further refined by Gregbased on the output to detect more types of files automatically and todistinguish between header and source .c files (which need differentcomment types.) Finally Greg ran the script using the .csv files togenerate the patches.Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman List of files: /linux-6.15/drivers/clocksource/i8253.c

a5a1d1c2 - clocksource: Use a plain u64 instead of cycle_t

Wed, 21 Dec 2016 19:32:01 +0000

clocksource: Use a plain u64 instead of cycle_tThere is no point in having an extra type for extra confusion. u64 isunambiguous.Conversion was done with the following coccinelle script:@rem@@@-typedef u64 cycle_t;@fix@typedef cycle_t;@@-cycle_t+u64Signed-off-by: Thomas Gleixner Cc: Peter Zijlstra Cc: John Stultz List of files: /linux-6.15/drivers/clocksource/i8253.c

8eda41b0 - clockevents/drivers/i8253: Migrate to new 'set-state' interface

Thu, 18 Jun 2015 10:54:22 +0000

clockevents/drivers/i8253: Migrate to new 'set-state' interfaceMigrate i8253 driver to the new 'set-state' interface provided byclockevents core, the earlier 'set-mode' interface is marked obsoletenow.This also enables us to implement callbacks for new states of clockeventdevices, for example: ONESHOT_STOPPED.Cc: Russell King Signed-off-by: Viresh Kumar Signed-off-by: Daniel Lezcano List of files: /linux-6.15/drivers/clocksource/i8253.c

d6ad4187 - time: Kill xtime_lock, replacing it with jiffies_lock

Wed, 29 Feb 2012 00:50:11 +0000

time: Kill xtime_lock, replacing it with jiffies_lockNow that timekeeping is protected by its own locks, renamethe xtime_lock to jifffies_lock to better describe what itprotects.CC: Thomas Gleixner CC: Eric Dumazet CC: Richard Cochran Signed-off-by: John Stultz List of files: /linux-6.15/drivers/clocksource/i8253.c

5f724e84 - time: x86: Replace LATCH with PIT_LATCH in i8253 clocksource driver

Tue, 01 Nov 2011 21:25:25 +0000

time: x86: Replace LATCH with PIT_LATCH in i8253 clocksource driverThe i8253 clockevent & clocksource driver uses PIT_LATCHexcept for two cases where it uses LATCH:1) /* VIA686a test code... reset the latch if count > max + 1 */ if (count > LATCH) {LATCH is based on CLOCK_TICK_RATE which is defined asPIT_TICK_RATE on x86 so this should just be the later.2) ... switch (mode) { case CLOCK_EVT_MODE_PERIODIC: /* binary, mode 2, LSB/MSB, ch 0 */ outb_p(0x34, PIT_MODE); outb_p(LATCH & 0xff , PIT_CH0); /* LSB */ outb_p(LATCH >> 8 , PIT_CH0); /* MSB */ ...MIPS and ARM are the only other arches that use this driver. Inthe MIPS case CLOCK_TICK_RATE is defined as the same value asPIT_TICK_RATE. For ARM, the only machine that uses it isFootbridge which has a totally bogus CLOCK_TICK_RATE accordingto the comments. Furthermore, the clockevent_i8253_init()initializes the clockevent with PIT_TIC_RATE, so there'sno reason to use the generic LATCH.This is part of work to remove and depecrate the globalCLOCK_TICK_RATE symbol.Signed-off-by: Deepak Saxena Signed-off-by: John Stultz List of files: /linux-6.15/drivers/clocksource/i8253.c

e6220bdc - i8253: Create common clockevent implementation

Thu, 09 Jun 2011 13:08:25 +0000

i8253: Create common clockevent implementationarm, mips and x86 implement i8253 based clockevents. All the same codecopied. Create a common implementation in drivers/clocksource/i8253.c.About time to rename drivers/clocksource/ to something else.Signed-off-by: Thomas Gleixner Cc: Russell King Cc: Ralf Baechle Cc: John Stultz Link: http://lkml.kernel.org/r/20110609130621.921710458@linutronix.de List of files: /linux-6.15/drivers/clocksource/i8253.c

21f07f4f - i8253: Export i8253_lock unconditionally

Thu, 09 Jun 2011 21:08:47 +0000

i8253: Export i8253_lock unconditionallyWe don't want to add endless selects and module ifdefs.Reported-by: Ingo Molnar Signed-off-by: Thomas Gleixner List of files: /linux-6.15/drivers/clocksource/i8253.c

609d4144 - i8253: Remove I8253_LOCK config

Fri, 03 Jun 2011 15:44:16 +0000

i8253: Remove I8253_LOCK configNow that all extra ifdeffed implementations are gone, depend the lockexport on PCSPKR_PLATFORMSigned-off-by: Thomas Gleixner Cc: Ralf Baechle Cc: Russell King List of files: /linux-6.15/drivers/clocksource/i8253.c

15f304b6 - i8253: Consolidate all kernel definitions of i8253_lock

Wed, 01 Jun 2011 18:04:59 +0000

i8253: Consolidate all kernel definitions of i8253_lockMove them to drivers/clocksource/i8253.c and remove theimplementations in arch/[ tglx: Avoid the extra file in lib - folded arch patches in. The export will become conditional in a later step ]Signed-off-by: Ralf Baechle Link: http://lkml.kernel.org/r/20110601180610.221426078@duck.linux-mips.netCc: Russell King Signed-off-by: Thomas Gleixner List of files: /linux-6.15/drivers/clocksource/i8253.c

334955ef - i8253: Create linux/i8253.h and use it in all 8253 related files

Wed, 01 Jun 2011 18:04:57 +0000

i8253: Create linux/i8253.h and use it in all 8253 related filesSigned-off-by: Ralf Baechle Cc: linux-mips@linux-mips.orgLink: http://lkml.kernel.org/r/20110601180610.054254048@duck.linux-mips.netSigned-off-by: Thomas Gleixner arch/arm/mach-footbridge/isa-timer.c | 2 +- arch/mips/cobalt/time.c | 2 +- arch/mips/jazz/irq.c | 2 +- arch/mips/kernel/i8253.c | 2 +- arch/mips/mti-malta/malta-time.c | 2 +- arch/mips/sgi-ip22/ip22-time.c | 2 +- arch/mips/sni/time.c | 2 +- arch/x86/kernel/apic/apic.c | 2 +- arch/x86/kernel/apm_32.c | 2 +- arch/x86/kernel/hpet.c | 2 +- arch/x86/kernel/i8253.c | 2 +- arch/x86/kernel/time.c | 2 +- drivers/block/hd.c | 2 +- drivers/clocksource/i8253.c | 2 +- drivers/input/gameport/gameport.c | 2 +- drivers/input/joystick/analog.c | 2 +- drivers/input/misc/pcspkr.c | 2 +- include/linux/i8253.h | 11 +++++++++++ sound/drivers/pcsp/pcsp.h | 2 +- 19 files changed, 29 insertions(+), 18 deletions(-) List of files: /linux-6.15/drivers/clocksource/i8253.c

89c0b8e2 - clocksource: add common i8253 PIT clocksource

Sun, 08 May 2011 17:47:58 +0000

clocksource: add common i8253 PIT clocksourceThis is based upon both arch/arm/mach-footbridge/isa-timer.c andarch/x86/kernel/i8253.c.Acked-by: John Stultz Acked-by: Thomas Gleixner Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Ralf Baechle Signed-off-by: Russell King List of files: /linux-6.15/drivers/clocksource/i8253.c