At Wed, 29 Oct 2014 10:48:10 -0700,
Tina Ruchandani wrote:
>
> es1968_measure_clock uses struct timeval, which on 32-bit systems will
> overflow
> in 2038, leading to incorrect interpretation of time.This patch changes the
> function to use ktime_t instead of struct timeval, which implies:
> - no y2038: ktime_t uses a 64-bit datatype explicitly.
> - efficent subtraction: The earlier version computes the difference in usecs
> while dealing with secs and nsecs. It requires checks to see if the nsecs of
> stop is less than start. This patch uses a direct subtract of ktime_t and
> converts to usecs.
> - use of monotonic clock (ktime_get) over real time (do_gettimeofday),
> which simplifies timekeeping, as it does not have to deal with cases
> where stop_time is less than start_time.
>
> Signed-off-by: Tina Ruchandani <[email protected]>
> Reviewed-by: Arnd Bergmann <[email protected]>
Applied, thanks.
Takashi
> ---
> sound/pci/es1968.c | 15 ++++++---------
> 1 file changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/sound/pci/es1968.c b/sound/pci/es1968.c
> index a9956a7..6039700 100644
> --- a/sound/pci/es1968.c
> +++ b/sound/pci/es1968.c
> @@ -1710,7 +1710,8 @@ static void es1968_measure_clock(struct es1968 *chip)
> int i, apu;
> unsigned int pa, offset, t;
> struct esm_memory *memory;
> - struct timeval start_time, stop_time;
> + ktime_t start_time, stop_time;
> + ktime_t diff;
>
> if (chip->clock == 0)
> chip->clock = 48000; /* default clock value */
> @@ -1761,12 +1762,12 @@ static void es1968_measure_clock(struct es1968 *chip)
> snd_es1968_bob_inc(chip, ESM_BOB_FREQ);
> __apu_set_register(chip, apu, 5, pa & 0xffff);
> snd_es1968_trigger_apu(chip, apu, ESM_APU_16BITLINEAR);
> - do_gettimeofday(&start_time);
> + start_time = ktime_get();
> spin_unlock_irq(&chip->reg_lock);
> msleep(50);
> spin_lock_irq(&chip->reg_lock);
> offset = __apu_get_register(chip, apu, 5);
> - do_gettimeofday(&stop_time);
> + stop_time = ktime_get();
> snd_es1968_trigger_apu(chip, apu, 0); /* stop */
> snd_es1968_bob_dec(chip);
> chip->in_measurement = 0;
> @@ -1777,12 +1778,8 @@ static void es1968_measure_clock(struct es1968 *chip)
> offset &= 0xfffe;
> offset += chip->measure_count * (CLOCK_MEASURE_BUFSIZE/2);
>
> - t = stop_time.tv_sec - start_time.tv_sec;
> - t *= 1000000;
> - if (stop_time.tv_usec < start_time.tv_usec)
> - t -= start_time.tv_usec - stop_time.tv_usec;
> - else
> - t += stop_time.tv_usec - start_time.tv_usec;
> + diff = ktime_sub(stop_time, start_time);
> + t = ktime_to_us(diff);
> if (t == 0) {
> dev_err(chip->card->dev, "?? calculation error..\n");
> } else {
> --
> 2.1.0.rc2.206.gedb03e5
>
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