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-rw-r--r--drivers/w1/slaves/w1_therm.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/drivers/w1/slaves/w1_therm.c b/drivers/w1/slaves/w1_therm.c
index fb28acaeed6c..e87f464a6fb0 100644
--- a/drivers/w1/slaves/w1_therm.c
+++ b/drivers/w1/slaves/w1_therm.c
@@ -37,6 +37,14 @@ MODULE_LICENSE("GPL");
MODULE_AUTHOR("Evgeniy Polyakov <johnpol@2ka.mipt.ru>");
MODULE_DESCRIPTION("Driver for 1-wire Dallas network protocol, temperature family.");
+/* Allow the strong pullup to be disabled, but default to enabled.
+ * If it was disabled a parasite powered device might not get the require
+ * current to do a temperature conversion. If it is enabled parasite powered
+ * devices have a better chance of getting the current required.
+ */
+static int w1_strong_pullup = 1;
+module_param_named(strong_pullup, w1_strong_pullup, int, 0);
+
static u8 bad_roms[][9] = {
{0xaa, 0x00, 0x4b, 0x46, 0xff, 0xff, 0x0c, 0x10, 0x87},
{}
@@ -192,9 +200,12 @@ static ssize_t w1_therm_read_bin(struct kobject *kobj,
int count = 0;
unsigned int tm = 750;
+ /* 750ms strong pullup (or delay) after the convert */
+ if (w1_strong_pullup)
+ w1_next_pullup(dev, tm);
w1_write_8(dev, W1_CONVERT_TEMP);
-
- msleep(tm);
+ if (!w1_strong_pullup)
+ msleep(tm);
if (!w1_reset_select_slave(sl)) {