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 <[email protected]> --- 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
