[PATCH v3 3/3] timer: riscv_aclint_timer: add timer_get_boot_us for BOOTSTAGE

[Heinrich Schuchardt]

On 06.09.23 07:18, Chanho Park wrote:
> timer_get_boot_us function is required to record the boot stages as
> us-based timestamp.
> To get a micro-second time from a timer tick, this converts the
> formula like below to avoid zero result of (tick / rate) part.
> 
> From: time(us) = (tick / rate) * 10000000

Where is the old implementation that you refer to?

> To  : time(us) = (tick * 1000) / (rate / 1000)
> 
> Signed-off-by: Chanho Park <chanho61.park at samsung.com>
> ---
>   drivers/timer/riscv_aclint_timer.c | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)
> 
> diff --git a/drivers/timer/riscv_aclint_timer.c b/drivers/timer/riscv_aclint_timer.c
> index e29d527c8d77..73fb87912851 100644
> --- a/drivers/timer/riscv_aclint_timer.c
> +++ b/drivers/timer/riscv_aclint_timer.c
> @@ -6,6 +6,7 @@
>   
>   #include <common.h>
>   #include <clk.h>
> +#include <div64.h>
>   #include <dm.h>
>   #include <timer.h>
>   #include <asm/io.h>
> @@ -44,6 +45,28 @@ u64 notrace timer_early_get_count(void)
>   }
>   #endif
>   
> +#if CONFIG_IS_ENABLED(RISCV_MMODE) && CONFIG_IS_ENABLED(BOOTSTAGE)
> +ulong timer_get_boot_us(void)
> +{
> +	int ret;
> +	u64 ticks = 0;
> +	u32 rate;
> +
> +	ret = dm_timer_init();
> +	if (!ret) {
> +		rate = timer_get_rate(gd->timer);
> +		timer_get_count(gd->timer, &ticks);
> +	} else {
> +		rate = RISCV_MMODE_TIMER_FREQ;
> +		ticks = readq((void __iomem *)MTIME_REG(RISCV_MMODE_TIMERBASE,
> +							RISCV_MMODE_TIMEROFF));
> +	}
> +
> +	/* Below is converted from time(us) = (tick / rate) * 10000000 */
> +	return lldiv(ticks * 1000, (rate / 1000));

I found similar code in drivers/timer/cadence-ttc.c and 
drivers/timer/omap-timer.c with

     us = (ticks * 1000) / rate;
     return us.

Either their code or yours must be wrong.

What I am missing in include/timer.h is a documentation that defines if 
timer_dev_priv.clock_rate and timer_get_rate() yield the frequency in Hz 
or kHz.

Once we have added the missing information in the include we can start 
reviewing this patch.

I really dislike that we have code per architecture and don't update and 
use a implementation in lib/time.c (where we also have an 
implementation) or drivers/timer/timer-uclass.c. Can't we have a single 
implementation which is driver model based and eliminate all others?

Best regards

Heinrich

> +}
> +#endif
> +
>   static const struct timer_ops riscv_aclint_timer_ops = {
>   	.get_count = riscv_aclint_timer_get_count,
>   };