Messages in this thread Patch in this message | | | Date | Fri, 28 Mar 2008 07:26:55 -0500 | From | David Fries <> | Subject | [PATCH 21/35] W1: w1_io.c reset comments and msleep |
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w1_io.c 1.7 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> --- 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 46c6994..9238758 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -291,12 +291,24 @@ 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; -- 1.4.4.4[unhandled content-type:application/pgp-signature] | |