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Date: Fri, 16 Mar 2012 22:25:41 +0100
From: Markus Franke <markus.franke@...02.tu-chemnitz.de>
To: linux-kernel@...r.kernel.org
CC: gregkh@...uxfoundation.org, Evgeniy Polyakov <zbr@...emap.net>
Subject: [PATCH 2/2] 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.
It applies to the current linux kernel git tree.
Signed-off-by: Markus Franke <franm@....tu-chemnitz.de>
---
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 3135b2c..e10acc2 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);
--
1.7.4.1
--
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