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Missed one change in the previous commit.

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Gregory Nutt 2017-05-21 15:02:00 -06:00
parent 7ffbb704d6
commit 32eb5ca99a
1 changed files with 16 additions and 5 deletions
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21
arch/arm/src/stm32l4/stm32l4_otgfshost.c
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@ -1956,14 +1956,25 @@ static ssize_t stm32l4_in_transfer(FAR struct stm32l4_usbhost_s *priv,
delay = 1000;
}
/* Wait for the next polling interval.
/* Wait for the next polling interval. For interrupt and
* isochronous endpoints, this is necessaryto assure the
* polling interval. It is used in other cases only to
* prevent the polling from consuming too much CPU bandwith.
*
* REVISIT: This delay could require more resolution than
* is provided by the system timer. In that case, the
* delay could be significantly longer than required.
* Small delays could require more resolution than is provided
* by the system timer. For example, if the system timer
* resolution is 10MS, then usleep(1000) will actually request
* a delay 20MS (due to both quantization and rounding).
*
* REVISIT: So which is better? To ignore tiny delays and
* hog the system bandwidth? Or to wait for an excessive
* amount and destroy system throughput?
*/
usleep(delay);
if (delay > CONFIG_USEC_PER_TICK)
{
usleep(delay - CONFIG_USEC_PER_TICK);
}
}
}
else