Hello Kaustabh, On 10/16/25 4:59 PM, Kaustabh Chakraborty wrote: > On 2025-10-15 07:48, Ahmad Fatoum wrote: >>> Thus, the only solution is to add a config option which, when enabled, >>> returns a hard coded value (CONFIG_COUNTER_FREQUENCY) instead of >>> querying >>> CNTFRQ_EL0. >> >> Why not read it from the clock-frequency property in the device tree? >> >> This is what barebox is now doing, incidentally also for Samsung >> support, see: >> https://lore.kernel.org/barebox/20250729203659.1858575-3- >> [email protected]/ > > In barebox, the timer is a device driver, like in linux. In U-Boot > however, it is > instead part of the ARM architecture specific code. And it is being > accessed by > a single function, not dependent on others.
Ah, I wasn't aware of this. > However, in U-Boot i found gd->arch.timer_rate_hz, which can be used, > like so: > > if (gd->arch.timer_rate_hz) > return gd->arch.timer_rate_hz; > > This property needs to be set in board file – in timer_init(). So I will do > that instead. :) Cheers, Ahmad > >> >> Cheers, >> Ahmad >> >>> >>> Signed-off-by: Kaustabh Chakraborty <[email protected]> >>> --- >>> arch/arm/cpu/armv8/Kconfig | 9 +++++++++ >>> arch/arm/cpu/armv8/generic_timer.c | 4 ++++ >>> 2 files changed, 13 insertions(+) >>> >>> diff --git a/arch/arm/cpu/armv8/Kconfig b/arch/arm/cpu/armv8/Kconfig >>> index >>> 199335cd6040d30a355a7fd5448a449fa7f550fb..d54d874b7caea200e1c05f522d8affe6d239a102 >>> 100644 >>> --- a/arch/arm/cpu/armv8/Kconfig >>> +++ b/arch/arm/cpu/armv8/Kconfig >>> @@ -4,6 +4,15 @@ config CMO_BY_VA_ONLY >>> bool "Force cache maintenance to be exclusively by VA" >>> depends on !SYS_DISABLE_DCACHE_OPS >>> >>> +config ARMV8_CNTFRQ_BROKEN >>> + bool "Fix broken ARMv8 generic timer" >>> + depends on COUNTER_FREQUENCY > 0 >>> + depends on SYS_ARCH_TIMER >>> + help >>> + Say Y here if there is no trustable firmware present which sets >>> + CNTFRQ_EL0 frequency before U-Boot. U-Boot will use the >>> + CONFIG_COUNTER_FREQUENCY value as the reported frequency. >>> + >>> config ARMV8_SPL_EXCEPTION_VECTORS >>> bool "Install crash dump exception vectors" >>> depends on SPL >>> diff --git a/arch/arm/cpu/armv8/generic_timer.c b/arch/arm/cpu/armv8/ >>> generic_timer.c >>> index >>> 1de7ec596fc7cbbc3e78a241f163bc0a4fcad6b6..409570cf6fda79527e296b958368b552900524b1 >>> 100644 >>> --- a/arch/arm/cpu/armv8/generic_timer.c >>> +++ b/arch/arm/cpu/armv8/generic_timer.c >>> @@ -19,6 +19,10 @@ DECLARE_GLOBAL_DATA_PTR; >>> unsigned long notrace get_tbclk(void) >>> { >>> unsigned long cntfrq; >>> + >>> + if (IS_ENABLED(CONFIG_ARMV8_CNTFRQ_BROKEN)) >>> + return CONFIG_COUNTER_FREQUENCY; >>> + >>> asm volatile("mrs %0, cntfrq_el0" : "=r" (cntfrq)); >>> return cntfrq; >>> } >>> >>> --- >>> base-commit: a5b3be1a37e19646b9d36c91f11b23f568be4f21 >>> change-id: 20251014-armv8-broken-cntfrq-f350f68fbf6e >>> >>> Best regards, >> >> >> -- >> Pengutronix e.K. | >> | >> Steuerwalder Str. 21 | http:// >> www.pengutronix.de/ | >> 31137 Hildesheim, Germany | Phone: >> +49-5121-206917-0 | >> Amtsgericht Hildesheim, HRA 2686 | Fax: >> +49-5121-206917-5555 | > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
