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Re: [PATCH V2 2/2] timer: imx-tpm: add imx tpm timer support

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  Re: [PATCH V2 2/2] timer: imx-tpm: add imx tpm timer support Alexander Stein <alexander.stein@systec-electronic.com> - 2017-06-13 10:30 +0200
    Re: [PATCH V2 2/2] timer: imx-tpm: add imx tpm timer support Dong Aisheng <dongas86@gmail.com> - 2017-06-19 17:40 +0200

#1664591 — Re: [PATCH V2 2/2] timer: imx-tpm: add imx tpm timer support

On Tuesday 13 June 2017 15:58:45, Dong Aisheng wrote:
> diff --git a/drivers/clocksource/timer-imx-tpm.c
> b/drivers/clocksource/timer-imx-tpm.c new file mode 100644
> index 0000000..940a4f75
> --- /dev/null
> +++ b/drivers/clocksource/timer-imx-tpm.c
> @@ -0,0 +1,227 @@
> [...]
> +static int tpm_set_next_event(unsigned long delta,
> +				struct clock_event_device *evt)
> +{
> +	unsigned long next, now;
> +
> +	next = readl(timer_base + TPM_CNT) + delta;
> +	writel(next, timer_base + TPM_C0V);
> +	now = readl(timer_base + TPM_CNT);

What about:
> now = readl(timer_base + TPM_CNT);
> next = now + delta;
> writel(next, timer_base + TPM_C0V);
> return 0;

> +	return (int)((next - now) <= 0) ? -ETIME : 0;

Can this error actually happen, even with your implementation?

Best regards,
Alexander

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#1669326

On Tue, Jun 13, 2017 at 10:19:47AM +0200, Alexander Stein wrote:
> On Tuesday 13 June 2017 15:58:45, Dong Aisheng wrote:
> > diff --git a/drivers/clocksource/timer-imx-tpm.c
> > b/drivers/clocksource/timer-imx-tpm.c new file mode 100644
> > index 0000000..940a4f75
> > --- /dev/null
> > +++ b/drivers/clocksource/timer-imx-tpm.c
> > @@ -0,0 +1,227 @@
> > [...]
> > +static int tpm_set_next_event(unsigned long delta,
> > +				struct clock_event_device *evt)
> > +{
> > +	unsigned long next, now;
> > +
> > +	next = readl(timer_base + TPM_CNT) + delta;
> > +	writel(next, timer_base + TPM_C0V);
> > +	now = readl(timer_base + TPM_CNT);
> 
> What about:
> > now = readl(timer_base + TPM_CNT);
> > next = now + delta;
> > writel(next, timer_base + TPM_C0V);
> > return 0;
> 
> > +	return (int)((next - now) <= 0) ? -ETIME : 0;
> 
> Can this error actually happen, even with your implementation?

Yes, i did observe some -ETIME when testing with nanosleep or
hrtimer during programing min_delta event, especially when system
is high loading. e.g. run GPU stress test.

Please also refer to another mail for details i just replied to Daniel.

Regards
Dong Aisheng

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