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w1: Disable irqs during 1-wire bus operations, extend 1-wire reset pulse

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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>
This commit is contained in:
Markus Franke 2012-04-12 00:42:03 +02:00 committed by Greg Kroah-Hartman
parent f19420c1ac
commit 8f1e12512e
1 changed files with 18 additions and 4 deletions
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22
drivers/w1/w1_io.c
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@ -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);