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Subject: Re: [PATCH 2/2] staging: greybus/loopback: use ktime_get() for time
 intervals
To:     Arnd Bergmann <arnd@arndb.de>, Johan Hovold <johan@kernel.org>,
        Alex Elder <elder@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Gioh Kim <gi-oh.kim@profitbricks.com>,
        Abdul Rauf <abdulraufmujahid@gmail.com>,
        Arushi Singhal <arushisinghal19971997@gmail.com>,
        greybus-dev@lists.linaro.org, devel@driverdev.osuosl.org,
        linux-kernel@vger.kernel.org
References: <20171102143304.851481-1-arnd@arndb.de>
 <20171102143304.851481-2-arnd@arndb.de>
From:   Bryan O'Donoghue <pure.logic@nexus-software.ie>
Message-ID: <61965985-d5c3-c231-1d18-5d14b1ce7b2d@nexus-software.ie>
Date:   Fri, 3 Nov 2017 10:28:47 +0000
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On 02/11/17 14:32, Arnd Bergmann wrote:
> This driver is the only one using the deprecated timeval_to_ns()
> helper. Changing it from do_gettimeofday() to ktime_get() makes
> the code more efficient, more robust against concurrent
> settimeofday(), more accurate and lets us get rid of that helper
> in the future.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>   drivers/staging/greybus/loopback.c | 42 ++++++++++++++++----------------------
>   1 file changed, 18 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/staging/greybus/loopback.c b/drivers/staging/greybus/loopback.c
> index 85046fb16aad..3d92638c424b 100644
> --- a/drivers/staging/greybus/loopback.c
> +++ b/drivers/staging/greybus/loopback.c
> @@ -58,7 +58,7 @@ static struct gb_loopback_device gb_dev;
>   struct gb_loopback_async_operation {
>   	struct gb_loopback *gb;
>   	struct gb_operation *operation;
> -	struct timeval ts;
> +	ktime_t ts;
>   	struct timer_list timer;
>   	struct list_head entry;
>   	struct work_struct work;
> @@ -81,7 +81,7 @@ struct gb_loopback {
>   	atomic_t outstanding_operations;
>   
>   	/* Per connection stats */
> -	struct timeval ts;
> +	ktime_t ts;
>   	struct gb_loopback_stats latency;
>   	struct gb_loopback_stats throughput;
>   	struct gb_loopback_stats requests_per_second;
> @@ -375,14 +375,9 @@ static u64 __gb_loopback_calc_latency(u64 t1, u64 t2)
>   		return NSEC_PER_DAY - t2 + t1;
>   }
>   
> -static u64 gb_loopback_calc_latency(struct timeval *ts, struct timeval *te)
> +static u64 gb_loopback_calc_latency(ktime_t ts, ktime_t te)
>   {
> -	u64 t1, t2;
> -
> -	t1 = timeval_to_ns(ts);
> -	t2 = timeval_to_ns(te);
> -
> -	return __gb_loopback_calc_latency(t1, t2);
> +	return __gb_loopback_calc_latency(ktime_to_ns(ts), ktime_to_ns(te));
>   }
>   
>   static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
> @@ -390,10 +385,10 @@ static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
>   				      void *response, int response_size)
>   {
>   	struct gb_operation *operation;
> -	struct timeval ts, te;
> +	ktime_t ts, te;
>   	int ret;
>   
> -	do_gettimeofday(&ts);
> +	ts = ktime_get();
>   	operation = gb_operation_create(gb->connection, type, request_size,
>   					response_size, GFP_KERNEL);
>   	if (!operation)
> @@ -421,10 +416,10 @@ static int gb_loopback_operation_sync(struct gb_loopback *gb, int type,
>   		}
>   	}
>   
> -	do_gettimeofday(&te);
> +	te = ktime_get();
>   
>   	/* Calculate the total time the message took */
> -	gb->elapsed_nsecs = gb_loopback_calc_latency(&ts, &te);
> +	gb->elapsed_nsecs = gb_loopback_calc_latency(ts, te);
>   
>   out_put_operation:
>   	gb_operation_put(operation);
> @@ -492,10 +487,10 @@ static void gb_loopback_async_operation_callback(struct gb_operation *operation)
>   {
>   	struct gb_loopback_async_operation *op_async;
>   	struct gb_loopback *gb;
> -	struct timeval te;
> +	ktime_t te;
>   	bool err = false;
>   
> -	do_gettimeofday(&te);
> +	te = ktime_get();
>   	op_async = gb_loopback_operation_find(operation->id);
>   	if (!op_async)
>   		return;
> @@ -512,8 +507,7 @@ static void gb_loopback_async_operation_callback(struct gb_operation *operation)
>   	}
>   
>   	if (!err)
> -		gb->elapsed_nsecs = gb_loopback_calc_latency(&op_async->ts,
> -							     &te);
> +		gb->elapsed_nsecs = gb_loopback_calc_latency(op_async->ts, te);
>   
>   	if (op_async->pending) {
>   		if (err)
> @@ -608,7 +602,7 @@ static int gb_loopback_async_operation(struct gb_loopback *gb, int type,
>   	list_add_tail(&op_async->entry, &gb_dev.list_op_async);
>   	spin_unlock_irqrestore(&gb_dev.lock, flags);
>   
> -	do_gettimeofday(&op_async->ts);
> +	op_async->ts = ktime_get();
>   	op_async->pending = true;
>   	atomic_inc(&gb->outstanding_operations);
>   	mutex_lock(&gb->mutex);
> @@ -842,7 +836,7 @@ static void gb_loopback_reset_stats(struct gb_loopback *gb)
>   	/* Should be initialized at least once per transaction set */
>   	gb->apbridge_latency_ts = 0;
>   	gb->gbphy_latency_ts = 0;
> -	memset(&gb->ts, 0, sizeof(struct timeval));
> +	gb->ts = ktime_set(0, 0);
>   }
>   
>   static void gb_loopback_update_stats(struct gb_loopback_stats *stats, u32 val)
> @@ -925,15 +919,15 @@ static void gb_loopback_calculate_stats(struct gb_loopback *gb, bool error)
>   {
>   	u64 nlat;
>   	u32 lat;
> -	struct timeval te;
> +	ktime_t te;
>   
>   	if (!error) {
>   		gb->requests_completed++;
>   		gb_loopback_calculate_latency_stats(gb);
>   	}
>   
> -	do_gettimeofday(&te);
> -	nlat = gb_loopback_calc_latency(&gb->ts, &te);
> +	te = ktime_get();
> +	nlat = gb_loopback_calc_latency(gb->ts, te);
>   	if (nlat >= NSEC_PER_SEC || gb->iteration_count == gb->iteration_max) {
>   		lat = gb_loopback_nsec_to_usec_latency(nlat);
>   
> @@ -1017,8 +1011,8 @@ static int gb_loopback_fn(void *data)
>   		size = gb->size;
>   		us_wait = gb->us_wait;
>   		type = gb->type;
> -		if (gb->ts.tv_usec == 0 && gb->ts.tv_sec == 0)
> -			do_gettimeofday(&gb->ts);
> +		if (ktime_to_ns(gb->ts) == 0)
> +			gb->ts = ktime_get();
>   		mutex_unlock(&gb->mutex);
>   
>   		/* Else operations to perform */
> 

This one I'd like to test first.

I'll get back to you

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