The ds2438 has a register in page1 called offset, which dictates
how the current measurement is done. If the offset register is not
calibrated well, pulling zero current from a battery shows a non-zero
current measurement.
Gives write access to the offset register. This way, a user following
the calibration steps explained in the datasheet can use this driver
to fully calibrate de current measurements.
Signed-off-by: Luiz Sampaio <sampaio....@gmail.com>
---
drivers/w1/slaves/w1_ds2438.c | 94 ++++++++++++++++++++++++++++++++++-
1 file changed, 92 insertions(+), 2 deletions(-)
diff --git a/drivers/w1/slaves/w1_ds2438.c b/drivers/w1/slaves/w1_ds2438.c
index 08f4b451c349..5d58986bb1a9 100644
--- a/drivers/w1/slaves/w1_ds2438.c
+++ b/drivers/w1/slaves/w1_ds2438.c
@@ -49,6 +49,15 @@
#define DS2438_CURRENT_MSB 0x06
#define DS2438_THRESHOLD 0x07
+/* Page #1 definitions */
+#define DS2438_ETM_0 0x00
+#define DS2438_ETM_1 0x01
+#define DS2438_ETM_2 0x02
+#define DS2438_ETM_3 0x03
+#define DS2438_ICA 0x04
+#define DS2438_OFFSET_LSB 0x05
+#define DS2438_OFFSET_MSB 0x06
+
static int w1_ds2438_get_page(struct w1_slave *sl, int pageno, u8 *buf)
{
unsigned int retries = W1_DS2438_RETRIES;
@@ -62,13 +71,13 @@ static int w1_ds2438_get_page(struct w1_slave *sl, int
pageno, u8 *buf)
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_RECALL_MEMORY;
- w1_buf[1] = pageno;
+ w1_buf[1] = (u8)pageno;
w1_write_block(sl->master, w1_buf, 2);
if (w1_reset_select_slave(sl))
continue;
w1_buf[0] = W1_DS2438_READ_SCRATCH;
- w1_buf[1] = pageno;
+ w1_buf[1] = (u8)pageno;
w1_write_block(sl->master, w1_buf, 2);
count = w1_read_block(sl->master, buf, DS2438_PAGE_SIZE + 1);
@@ -182,6 +191,34 @@ static int w1_ds2438_change_config_bit(struct w1_slave
*sl, u8 mask, u8 value)
return -1;
}
+static int w1_ds2438_change_offset_register(struct w1_slave *sl, u8 *value)
+{
+ unsigned int retries = W1_DS2438_RETRIES;
+ u8 w1_buf[9];
+ u8 w1_page1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
+
+ if (w1_ds2438_get_page(sl, 1, w1_page1_buf) == 0) {
+ memcpy(&w1_buf[2], w1_page1_buf, DS2438_PAGE_SIZE - 1); /* last
register is reserved */
+ w1_buf[7] = value[0]; /* change only offset register */
+ w1_buf[8] = value[1];
+ while (retries--) {
+ if (w1_reset_select_slave(sl))
+ continue;
+ w1_buf[0] = W1_DS2438_WRITE_SCRATCH;
+ w1_buf[1] = 0x01; /* write to page 1 */
+ w1_write_block(sl->master, w1_buf, 9);
+
+ if (w1_reset_select_slave(sl))
+ continue;
+ w1_buf[0] = W1_DS2438_COPY_SCRATCH;
+ w1_buf[1] = 0x01;
+ w1_write_block(sl->master, w1_buf, 2);
+ return 0;
+ }
+ }
+ return -1;
+}
+
static int w1_ds2438_get_voltage(struct w1_slave *sl,
int adc_input, uint16_t *voltage)
{
@@ -323,6 +360,55 @@ static ssize_t page0_read(struct file *filp, struct
kobject *kobj,
return ret;
}
+static ssize_t page1_read(struct file *filp, struct kobject *kobj,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t off, size_t count)
+{
+ struct w1_slave *sl = kobj_to_w1_slave(kobj);
+ int ret;
+ u8 w1_buf[DS2438_PAGE_SIZE + 1 /*for CRC*/];
+
+ if (off != 0)
+ return 0;
+ if (!buf)
+ return -EINVAL;
+
+ mutex_lock(&sl->master->bus_mutex);
+
+ /* Read no more than page1 size */
+ if (count > DS2438_PAGE_SIZE)
+ count = DS2438_PAGE_SIZE;
+
+ if (w1_ds2438_get_page(sl, 1, w1_buf) == 0) {
+ memcpy(buf, &w1_buf, count);
+ ret = count;
+ } else
+ ret = -EIO;
+
+ mutex_unlock(&sl->master->bus_mutex);
+
+ return ret;
+}
+
+static ssize_t offset_write(struct file *filp, struct kobject *kobj,
+ struct bin_attribute *bin_attr, char *buf,
+ loff_t off, size_t count)
+{
+ struct w1_slave *sl = kobj_to_w1_slave(kobj);
+ int ret;
+
+ mutex_lock(&sl->master->bus_mutex);
+
+ if (w1_ds2438_change_offset_register(sl, buf) == 0)
+ ret = count;
+ else
+ ret = -EIO;
+
+ mutex_unlock(&sl->master->bus_mutex);
+
+ return ret;
+}
+
static ssize_t temperature_read(struct file *filp, struct kobject *kobj,
struct bin_attribute *bin_attr, char *buf,
loff_t off, size_t count)
@@ -388,6 +474,8 @@ static ssize_t vdd_read(struct file *filp, struct kobject
*kobj,
static BIN_ATTR(iad, 0664, iad_read, iad_write, 0);
static BIN_ATTR_RO(page0, DS2438_PAGE_SIZE);
+static BIN_ATTR_RO(page1, DS2438_PAGE_SIZE);
+static BIN_ATTR_WO(offset, 2);
static BIN_ATTR_RO(temperature, 0/* real length varies */);
static BIN_ATTR_RO(vad, 0/* real length varies */);
static BIN_ATTR_RO(vdd, 0/* real length varies */);
@@ -395,6 +483,8 @@ static BIN_ATTR_RO(vdd, 0/* real length varies */);
static struct bin_attribute *w1_ds2438_bin_attrs[] = {
&bin_attr_iad,
&bin_attr_page0,
+ &bin_attr_page1,
+ &bin_attr_offset,
&bin_attr_temperature,
&bin_attr_vad,
&bin_attr_vdd,
--
2.30.1
