diff options
| author | David Fries <david@fries.net> | 2008-10-15 22:05:01 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-10-16 11:21:50 -0700 |
| commit | 8e3dae2b4727dc216e2dc16d2f0271b5f31b680c (patch) | |
| tree | 9f6889372940cbccb57631ac487ad5c94aa5b430 /drivers/w1 | |
| parent | 7dc8f527ef20bf95143dfbe2ecc01dc70b1e6ab7 (diff) | |
| download | lwn-8e3dae2b4727dc216e2dc16d2f0271b5f31b680c.tar.gz lwn-8e3dae2b4727dc216e2dc16d2f0271b5f31b680c.zip | |
W1: w1_io.c reset comments and msleep
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>
Diffstat (limited to 'drivers/w1')
| -rw-r--r-- | drivers/w1/w1_io.c | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c index 97b338a16abc..f4f82f1f486e 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -293,12 +293,24 @@ int w1_reset_bus(struct w1_master *dev) result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1; else { 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); dev->bus_master->write_bit(dev->bus_master->data, 1); w1_delay(70); 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; |