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1c4b87c921
linux/drivers/clocksource
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Markus Schneider-Pargmann 1c4b87c921 clocksource/drivers/arm_global_timer: Add auto-detection for initial prescaler values 
am43xx has a clock tree where the global timer clock is an indirect child
of the CPU clock used for frequency scaling:

  dpll_mpu_ck -- CPU/cpufreq
        |
        v
  dpll_mpu_m2_ck -- divider
        |
        v
  mpu_periphclk -- fixed divider by 2 used for global timer

When CPU frequency changes, the global timer's clock notifier rejects
the change because the hardcoded prescaler (1 or 2) cannot accommodate
the frequency range across all CPU OPPs (300, 600, 720, 800, 1000 MHz).

Add platform-specific prescaler auto-detection to solve this issue:

- am43xx: prescaler = 50 (calculated as initial_freq/GCD of all OPP
  freqs) This allows the timer to work across all CPU frequencies after
  the fixed divider by 2. Tested on am4372-idk-evm.

- zynq-7000: prescaler = 2 (preserves previous Kconfig default)

- Other platforms: prescaler = 1 (previous default)

The Kconfig option now defaults to 0 (auto-detection) but can still
override the auto-detected value when set to a non-zero value,
preserving existing customization workflows.

Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Patrice Chotard <patrice.chotard@foss.st.com>
Tested-by: Judith Mendez <jm@ti.com>
Reviewed-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/20250819-topic-am43-arm-global-timer-v6-16-v2-1-6d082e2a5161@baylibre.com
2025-09-23 12:41:58 +02:00
..
acpi_pm.c clocksource: acpi_pm: Add external callback for suspend/resume 2024-09-06 14:49:20 +02:00
arc_timer.c clocksource/drivers/arc_timer: Eliminate redefined macro error 2021-10-16 22:15:01 +02:00
arm_arch_timer_mmio.c clocksource/drivers/arm_arch_timer_mmio: Add MMIO clocksource 2025-09-23 12:32:08 +02:00
arm_arch_timer.c clocksource/drivers/arm_arch_timer_mmio: Switch over to standalone driver 2025-09-23 12:31:50 +02:00
arm_global_timer.c clocksource/drivers/arm_global_timer: Add auto-detection for initial prescaler values 2025-09-23 12:41:58 +02:00
armv7m_systick.c
asm9260_timer.c clocksource/drivers/asm9260: Add missing clk_disable_unprepare in asm9260_timer_init 2024-09-06 14:49:21 +02:00
bcm_kona_timer.c clocksource/drivers/bcm_kona: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
bcm2835_timer.c clocksource: Explicitly include correct DT includes 2023-08-28 13:30:57 -05:00
clksrc_st_lpc.c
clksrc-dbx500-prcmu.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
clps711x-timer.c
dummy_timer.c
dw_apb_timer_of.c clocksource/drivers/dw_apb_timer_of: Fix probe failure 2021-12-10 17:46:54 +01:00
dw_apb_timer.c clocksource/drivers/dw_apb: Remove unused dw_apb_clockevent functions 2024-11-13 13:49:33 +01:00
em_sti.c clocksource: remove MODULE_LICENSE in non-modules 2023-04-13 13:13:51 -07:00
exynos_mct.c clocksource/drivers/exynos_mct: Fixed a spelling error 2025-03-07 17:55:59 +01:00
hyperv_timer.c clocksource: hyper-v: Fix warnings for missing export.h header inclusion 2025-07-09 23:46:06 +00:00
i8253.c clocksource/i8253: Use raw_spinlock_irqsave() in clockevent_i8253_disable() 2025-05-05 15:34:49 +02:00
ingenic-ost.c clocksource/drivers/ingenic: Use devm_clk_get_enabled() helpers 2024-09-06 14:49:20 +02:00
ingenic-sysost.c clocksource/drivers/ingenic-sysost: Convert from round_rate() to determine_rate() 2025-09-23 12:41:50 +02:00
ingenic-timer.c clocksource/drivers/ingenic-timer: Use pm_sleep_ptr() macro 2023-06-19 16:17:42 +02:00
jcore-pit.c irqchip/jcore-aic, clocksource/drivers/jcore: Fix jcore-pit interrupt request 2025-02-17 23:27:49 +01:00
Kconfig clocksource/drivers/arm_global_timer: Add auto-detection for initial prescaler values 2025-09-23 12:41:58 +02:00
Makefile clocksource/drivers/arm_arch_timer_mmio: Switch over to standalone driver 2025-09-23 12:31:50 +02:00
mips-gic-timer.c clocksource: mips-gic-timer: Enable counter when CPUs start 2025-02-21 10:19:14 +01:00
mmio.c
mps2-timer.c clocksource/drivers/mps2-timer: Use semicolons rather than commas to separate statements 2020-10-01 10:07:26 +02:00
mxs_timer.c clocksource/drivers/mxs_timer: Add missing semicolon when DEBUG is defined 2021-01-18 22:28:59 +01:00
nomadik-mtu.c clocksource: Explicitly include correct DT includes 2023-08-28 13:30:57 -05:00
numachip.c
renesas-ostm.c clocksource/drivers/renesas-ostm: Unconditionally enable reprobe support 2025-05-16 13:33:11 +02:00
samsung_pwm_timer.c of: remove internal arguments from of_property_for_each_u32() 2024-07-25 06:53:47 -05:00
scx200_hrt.c clocksource/drivers/scx200: Add module owner 2025-09-23 10:21:24 +02:00
sh_cmt.c clocksource/drivers/sh_cmt: Address race condition for clock events 2024-07-12 16:07:05 +02:00
sh_mtu2.c Timekeeping and clocksource/event driver updates the second batch: 2023-04-29 10:24:30 -07:00
sh_tmu.c clocksource: remove MODULE_LICENSE in non-modules 2023-04-13 13:13:51 -07:00
timer-armada-370-xp.c clocksource/drivers/armada-370-xp: Remove clockevents shutdown call on offlining 2024-10-31 10:41:43 +01:00
timer-atmel-pit.c
timer-atmel-st.c clocksource/drivers/atmel-st: Remove useless 'status' 2020-04-15 10:57:15 +02:00
timer-atmel-tcb.c clocksource/drivers/timer-atmel-tcb: Fix initialization on SAM9 hardware 2023-10-13 12:56:50 +02:00
timer-cadence-ttc.c clocksource/drivers/cadence-ttc: Add missing clk_disable_unprepare in ttc_setup_clockevent 2024-09-06 14:49:21 +02:00
timer-clint.c riscv: Use IPIs for remote cache/TLB flushes by default 2024-04-29 10:49:26 -07:00
timer-cs5535.c clocksource/drivers/cs5535: Add module owner 2025-09-23 10:52:23 +02:00
timer-davinci.c clocksource/drivers/davinci: Fix memory leak in davinci_timer_register when init fails 2023-04-24 16:56:13 +02:00
timer-digicolor.c clocksource/drivers/digicolor: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-econet-en751221.c clocksource/timer-econet-en751221: Convert comma to semicolon 2025-09-23 10:56:13 +02:00
timer-ep93xx.c clocksource/drivers/ep93xx: Fix error handling during probe 2023-12-27 15:37:11 +01:00
timer-fsl-ftm.c timekeeping, clocksource: Fix various typos in comments 2021-03-22 23:06:48 +01:00
timer-fttmr010.c clocksource/drivers/fttmr010: Pass around less pointers 2021-08-14 10:49:49 +02:00
timer-goldfish.c clocksource/drivers: Add a goldfish-timer clocksource 2022-04-11 11:48:01 +02:00
timer-gx6605s.c clocksource/drivers/timer-gx6605s: Fixup counter reload 2020-08-24 13:01:39 +02:00
timer-gxp.c clocksource/drivers/gpx: Remove redundant casts 2024-11-13 13:49:33 +01:00
timer-imx-gpt.c clocksource/drivers/imx: Fix -Wunused-but-set-variable warning 2024-01-22 13:11:02 +01:00
timer-imx-sysctr.c clocksource/drivers/imx-sysctr: Add i.MX95 support 2024-02-18 10:45:36 +01:00
timer-imx-tpm.c clocksource/drivers/imx-tpm: Fix next event not taking effect sometime 2024-09-02 10:04:15 +02:00
timer-integrator-ap.c clocksource: Explicitly include correct DT includes 2023-08-28 13:30:57 -05:00
timer-ixp4xx.c clocksource/drivers/ixp4xx: Drop boardfile probe path 2022-05-18 11:08:52 +02:00
timer-keystone.c
timer-loongson1-pwm.c clocksource/drivers/loongson1: Set variable ls1x_timer_lock storage-class-specifier to static 2023-08-18 12:13:03 +02:00
timer-lpc32xx.c clocksource/drivers/lpc32xx: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-mediatek-cpux.c clocksource/drivers/timer-mediatek: Split out CPUXGPT timers 2023-04-24 16:56:13 +02:00
timer-mediatek.c clocksource/drivers/timer-mediatek: Split out CPUXGPT timers 2023-04-24 16:56:13 +02:00
timer-meson6.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-microchip-pit64b.c clocksource/drivers/timer-microchip-pit64b: Add delay timer 2023-02-13 13:10:17 +01:00
timer-milbeaut.c
timer-mp-csky.c
timer-msc313e.c clocksource/drivers/msc313e: Add support for ssd20xd-based platforms 2021-12-20 13:28:39 +01:00
timer-npcm7xx.c clocksource/drivers/timer-npcm7xx: Enable timer 1 clock before use 2022-12-02 12:48:28 +01:00
timer-nxp-pit.c clocksource/drivers/nxp-pit: Add NXP Automotive s32g2 / s32g3 support 2025-09-23 12:30:19 +02:00
timer-nxp-stm.c clocksource/drivers/stm: Add module owner 2025-09-23 10:52:13 +02:00
timer-of.c clocksource/drivers/timer-of: Remove percpu irq related code 2024-09-02 10:04:15 +02:00
timer-of.h clocksource/drivers/timer-of: Remove percpu irq related code 2024-09-02 10:04:15 +02:00
timer-orion.c arm: Handle KCOV __init vs inline mismatches 2025-07-21 21:43:39 -07:00
timer-owl.c
timer-pistachio.c clocksource/drivers/pistachio: Convert to SPDX identifier 2022-05-18 11:08:59 +02:00
timer-probe.c treewide: Convert macro and uses of __section(foo) to __section("foo") 2020-10-25 14:51:49 -07:00
timer-pxa.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-qcom.c clocksource/drivers/qcom: Remove clockevents shutdown call on offlining 2024-10-31 10:41:43 +01:00
timer-ralink.c clocksource/drivers/ralink: Add Ralink System Tick Counter driver 2024-11-13 13:49:33 +01:00
timer-rda.c
timer-riscv.c clocksource/drivers/timer-riscv: Stop stimecmp when cpu hotplug 2025-03-18 12:59:03 +00:00
timer-rockchip.c
timer-rtl-otto.c clocksource/drivers/timer-rtl-otto: Simplify documentation 2025-09-23 12:41:26 +02:00
timer-sp.h clocksource/drivers/sp804: Enable Hisilicon sp804 timer 64bit mode 2020-09-24 10:51:04 +02:00
timer-sp804.c clocksource/drivers/sp804: Do not use timer namespace for timer_shutdown() function 2022-11-24 15:09:10 +01:00
timer-sprd.c
timer-stm32-lp.c clocksource/drivers/stm32-lp: Add module owner 2025-09-23 10:51:21 +02:00
timer-stm32.c clocksource/drivers/stm32: Fix all kernel-doc warnings 2024-01-22 13:15:38 +01:00
timer-sun4i.c clocksource/drivers/timer-sun4i: Add CLOCK_EVT_FEAT_DYNIRQ 2023-02-13 13:10:17 +01:00
timer-sun5i.c clocksource/drivers/sun5i: Add module owner 2025-09-23 10:51:44 +02:00
timer-tegra.c clocksource/drivers/timer-tegra: Remove clockevents shutdown call on offlining 2024-10-31 10:41:43 +01:00
timer-tegra186.c clocksource/drivers/timer-tegra186: Don't print superfluous errors 2025-09-23 12:41:39 +02:00
timer-ti-32k.c clocksource/drivers/ti-32K: Fix misuse of "/**" comment 2024-01-22 13:16:32 +01:00
timer-ti-dm-systimer.c clocksource/drivers/arm_arch_timer: Use of_property_present() for non-boolean properties 2024-11-13 13:49:33 +01:00
timer-ti-dm.c clocksource/drivers/timer-ti-dm : Capture functionality for OMAP DM timer 2025-09-23 12:32:40 +02:00
timer-versatile.c clocksource/drivers/timer-versatile: Clear OF_POPULATED flag 2020-05-23 00:03:25 +02:00
timer-vt8500.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00
timer-zevio.c clocksource: Replace setup_irq() by request_irq() 2020-02-27 12:15:24 +01:00