[PATCH 1/2] timer: tsc_timer: Fix FTRACE support

[Heinrich Schuchardt]

On 12/17/25 08:25, Patrick Rudolph wrote:
> Currently FTRACE aborts on the first function call since getting the
> timestamp causes a recursion and tracing is immediately disabled.
> 
> Fix that by adding 'notrace' to TSC timer functions.
> TEST=The 'trace' cmd reports that functions have been traced on
>       qemu-q35 when CONFIG_TRACE is enabled and FTRACE=1.
> 
> Signed-off-by: Patrick Rudolph <patrick.rudolph at 9elements.com>
> ---
>   drivers/timer/tsc_timer.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/timer/tsc_timer.c b/drivers/timer/tsc_timer.c
> index dd16ab320b2..d17fb2337dc 100644
> --- a/drivers/timer/tsc_timer.c
> +++ b/drivers/timer/tsc_timer.c
> @@ -395,14 +395,14 @@ void __udelay(unsigned long usec)
>   #endif
>   }
>   
> -static u64 tsc_timer_get_count(struct udevice *dev)
> +static u64 notrace tsc_timer_get_count(struct udevice *dev)
>   {
>   	u64 now_tick = rdtsc();
>   
>   	return now_tick - gd->arch.tsc_base;
>   }
>   
> -static void tsc_timer_ensure_setup(bool early)
> +static void notrace tsc_timer_ensure_setup(bool early)
>   {
>   	if (gd->arch.tsc_inited)
>   		return;

Thank you for reporting your issues with the FTRACE functionality and 
providing a fix for the x86 platform.

In __cyg_profile_func_enter() and __cyg_profile_func_exit() we call 
add_ftrace().

In function add_ftrace() we call timer_get_us().

In drivers/timer/tsc_timer.c this function is marked notrace but not in 
arch/arm/cpu/armv7/s5p-common/timer.c and not in arch/xtensa/lib/time.c.

The drivers/timer/tsc_timer.c implementation calls get_ticks() and 
get_tbclk_mhz().

get_ticks() is marked notrace in lib/time.c but nowhere else.

get_ticks() in lib/time.c calls timer_get_count() implemented in 
drivers/timer/timer-uclass.c which is marked notrace.

If CONFIG_TIMER_EARLY=y get_ticks() will call timer_early_get_count() 
when the timer driver is not set-up yet.

Very few driver implementations of timer_get_count() are marked as 
notrace (e.g. sandbox, risc-v).

Notrace function xtimer_early_get_rate() calls tsc_timer_ensure_setup().

My conclusion is that function tracing will fail on many more platforms 
than only x86.

Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>