Re: [PATCH V3 2/2] timer: imx-tpm: add imx tpm timer support

From: Thomas Gleixner
Date: Tue Jul 04 2017 - 10:09:55 EST

On Tue, 4 Jul 2017, Dong Aisheng wrote:

> IMX Timer/PWM Module (TPM) supports both timer and pwm function while
> this patch only adds the timer support. PWM would be added later.
> The TPM counter, compare and capture registers are clocked by an
> asynchronous clock that can remain enabled in low power modes.
> Due to the possible bus fabric contention, the CNT write may
> take a few more cycles and we need add ETIME check in case current
> delta event program gets missed.
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> Cc: Arnd Bergmann <arnd@xxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
> Cc: Anson Huang <Anson.Huang@xxxxxxx>
> Cc: Bai Ping <ping.bai@xxxxxxx>
> Signed-off-by: Dong Aisheng <aisheng.dong@xxxxxxx>
> ---
> ChangeLog:
> v2->v3:
> * address all comments from Daniel Lezcano
> * add more explaination on ETIME check in commit message

Actually the logic wants to be explained in a comment inside the function
as well.

I'm really impressed, that 10 years after we discovered the HPET disaster
(See comment in arch/x86/kernel/hpet.c::hpet_next_event) the same hardware
idiocy comes around again....