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| author | Markus Franke <markus.franke@s2002.tu-chemnitz.de> | 2012-04-12 00:42:03 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-04-11 16:44:10 -0700 |
| commit | 8f1e12512e9f1276b68c8b14a60961658c73336f (patch) | |
| tree | 370742441c08ea56dae64e9d7cfa9b53bad3d75a /drivers/w1/w1_io.c | |
| parent | f19420c1acb0b573c88a12deb2d42035e22d4a17 (diff) | |
| download | lwn-8f1e12512e9f1276b68c8b14a60961658c73336f.tar.gz lwn-8f1e12512e9f1276b68c8b14a60961658c73336f.zip | |
w1: Disable irqs during 1-wire bus operations, extend 1-wire reset pulse
This patch offers the possibility to disables irqs during w1_write_bit()
and w1_reset_bus() operations as timing requirements are very strict for
the 1-wire bus protocol. Per default interrupts are enabled but can be
disabled via the module parameter "w1_disable_irqs".
Extend 1-wire reset pulse length from 480us to 500us as 480us is the
minimum requirement for the 1-wire reset/presence pulse.
Signed-off-by: Markus Franke <franm@hrz.tu-chemnitz.de>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/w1/w1_io.c')
| -rw-r--r-- | drivers/w1/w1_io.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/drivers/w1/w1_io.c b/drivers/w1/w1_io.c index 3135b2c63998..e10acc237733 100644 --- a/drivers/w1/w1_io.c +++ b/drivers/w1/w1_io.c @@ -31,6 +31,9 @@ static int w1_delay_parm = 1; module_param_named(delay_coef, w1_delay_parm, int, 0); +static int w1_disable_irqs = 0; +module_param_named(disable_irqs, w1_disable_irqs, int, 0); + static u8 w1_crc8_table[] = { 0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65, 157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220, @@ -79,6 +82,10 @@ static u8 w1_touch_bit(struct w1_master *dev, int bit) */ static void w1_write_bit(struct w1_master *dev, int bit) { + unsigned long flags = 0; + + if(w1_disable_irqs) local_irq_save(flags); + if (bit) { dev->bus_master->write_bit(dev->bus_master->data, 0); w1_delay(6); @@ -90,6 +97,8 @@ static void w1_write_bit(struct w1_master *dev, int bit) dev->bus_master->write_bit(dev->bus_master->data, 1); w1_delay(10); } + + if(w1_disable_irqs) local_irq_restore(flags); } /** @@ -158,7 +167,7 @@ EXPORT_SYMBOL_GPL(w1_write_8); static u8 w1_read_bit(struct w1_master *dev) { int result; - unsigned long flags; + unsigned long flags = 0; /* sample timing is critical here */ local_irq_save(flags); @@ -318,6 +327,9 @@ EXPORT_SYMBOL_GPL(w1_read_block); int w1_reset_bus(struct w1_master *dev) { int result; + unsigned long flags = 0; + + if(w1_disable_irqs) local_irq_save(flags); if (dev->bus_master->reset_bus) result = dev->bus_master->reset_bus(dev->bus_master->data) & 0x1; @@ -330,19 +342,21 @@ int w1_reset_bus(struct w1_master *dev) * cpu for such a short amount of time AND get it back in * the maximum amount of time. */ - w1_delay(480); + w1_delay(500); dev->bus_master->write_bit(dev->bus_master->data, 1); w1_delay(70); result = dev->bus_master->read_bit(dev->bus_master->data) & 0x1; - /* minmum 70 (above) + 410 = 480 us + /* minmum 70 (above) + 430 = 500 us * There aren't any timing requirements between a reset and * the following transactions. Sleeping is safe here. */ - /* w1_delay(410); min required time */ + /* w1_delay(430); min required time */ msleep(1); } + if(w1_disable_irqs) local_irq_restore(flags); + return result; } EXPORT_SYMBOL_GPL(w1_reset_bus); |