linux-kernel - Re: [PATCH v4 1/4] Produce system time from correlated clocksource

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Date:	Tue, 13 Oct 2015 07:26:13 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	"Christopher S. Hall" <christopher.s.hall@...el.com>
Cc:	jeffrey.t.kirsher@...el.com, hpa@...or.com, mingo@...hat.com,
	tglx@...utronix.de, john.stultz@...aro.org, peterz@...radead.org,
	x86@...nel.org, intel-wired-lan@...ts.osuosl.org,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	kevin.b.stanton@...el.com
Subject: Re: [PATCH v4 1/4] Produce system time from correlated clocksource

On Mon, Oct 12, 2015 at 11:45:19AM -0700, Christopher S. Hall wrote:
> +int get_correlated_timestamp(struct correlated_ts *crt,
> +			     struct correlated_cs *crs)
> +{
> +	struct timekeeper *tk = &tk_core.timekeeper;
> +	unsigned long seq;
> +	cycles_t cycles, cycles_now, cycles_last;
> +	ktime_t base;
> +	s64 nsecs;
> +	int ret;
> +
> +	do {
> +		seq = read_seqcount_begin(&tk_core.seq);
> +		/*
> +		 * Verify that the correlated clocksoure is related to
> +		 * the currently installed timekeeper clocksoure
> +		 */
> +		if (tk->tkr_mono.clock != crs->related_cs)
> +			return -ENODEV;
> +
> +		/*
> +		 * Get a timestamp from the device if get_ts is non-NULL
> +		 */
> +		if( crt->get_ts ) {

CodingStyle.

> +			ret = crt->get_ts(crt);
> +			if (ret)
> +				return ret;
> +		}
> +
> +		/*
> +		 * Convert the timestamp to timekeeper clock cycles
> +		 */
> +		cycles = crs->convert(crs, crt->system_ts);
> +
> +		/*
> +		 * If we have get_ts is valid, we know the cycles value
> +		 * value is up to date and we can just do the conversion
> +		 */
> +		if( crt->get_ts )

Ditto.

> +			goto do_convert;
> +

Thanks,
Richard
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