Re: [PATCH 2/6] timer: orion-timer: Add timer_get_boot_us() for BOOTSTAGE support

Stefan Roese
2022-09-01T05:33:44Z

Hi Simon,

On 31.08.22 19:44, Simon Glass wrote:

<snip>

>>> It is needed because bootstage is called before driver model is ready.
>>> In fact it can be used to time driver model things.
>>
>> I see, makes sense. This brings up my next questions though, why isn't
>> CONFIG_TIMER_EARLY enough in this case? AFAICT it's targeted exactly
>> for this early (pre DM) bootstage. From drivers/timer/Kconfig:
>>
>> config TIMER_EARLY
>> bool "Allow timer to be used early in U-Boot"
>> depends on TIMER
>> # initr_bootstage() requires a timer and is called before initr_dm()
>> # so only the early timer is available
>> default y if X86 && BOOTSTAGE
>> help
>> In some cases the timer must be accessible before driver model is
>> active. Examples include when using CONFIG_TRACE to trace U-Boot's
>> execution before driver model is set up. Enable this option to
>> use an early timer. These functions must be supported by your timer
>> driver: timer_early_get_count() and timer_early_get_rate().
>>
>> So again, do we really need timer_get_boot_us() or isn't it enough
>> to select TIMER_EARLY when BOOTSTAGE is enabled?
>
> The timer is for milliseconds but for bootstage we need microseconds.
>
> Perhaps the ultimate solution here is to support a microsecond timer
> through the TIMER api and use the TIMER_EARLY thing to provide
> timer_get_boot_us(), perhaps renaming to timer_early_get_us() ?

Yes, sounds like a plan. We should consolidate these implementations.
Let me think about it and perhaps do some basic implementations and
tests for a while.

Thanks,
Stefan