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W1: w1_io.c reset comments and msleep

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w1_reset_bus, added some comments about the timing and switched to msleep
for the later delay.  I don't have the hardware to test the sleep after
reset change.  The one wire doesn't have a timing requirement between
commands so it is fine.  I do have the USB hardware and it would be in big
trouble with 10ms interrupt transfers to find that the reset completed.

Signed-off-by: David Fries <david@fries.net>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Fries 2008-10-15 22:05:01 -07:00 committed by Linus Torvalds
parent 7dc8f527ef
commit 8e3dae2b47
1 changed files with 13 additions and 1 deletions
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14
drivers/w1/w1_io.c
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@ -293,12 +293,24 @@ int w1_reset_bus(struct w1_master *dev)
result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1; result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1;
else { else {
dev->bus_master->write_bit(dev->bus_master->data, 0); dev->bus_master->write_bit(dev->bus_master->data, 0);
/* minimum 480, max ? us
* be nice and sleep, except 18b20 spec lists 960us maximum,
* so until we can sleep with microsecond accuracy, spin.
* Feel free to come up with some other way to give up the
* cpu for such a short amount of time AND get it back in
* the maximum amount of time.
*/
w1_delay(480); w1_delay(480);
dev->bus_master->write_bit(dev->bus_master->data, 1); dev->bus_master->write_bit(dev->bus_master->data, 1);
w1_delay(70); w1_delay(70);
result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1; result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1;
w1_delay(410); /* minmum 70 (above) + 410 = 480 us
* There aren't any timing requirements between a reset and
* the following transactions. Sleeping is safe here.
*/
/* w1_delay(410); min required time */
msleep(1);
} }
return result; return result;