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sensor: bq274xx: implement the bq27427 ccgain workaround

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The BQ27427 appears to work incorrectly with the ROM configuration
value, it battery power and current are the inverse of what they should
be, and SoC is decresing when charging and increasing when discharging
as a consequence.

At this time this only appears documented in the TI E2E forums, and the
workaround seems to be to invert the sign of the CC Sense register of
the device.

This register is not documented on the BQ27427 device technical
reference manual, as the device has an internal shut and the sense value
should not have to be tweaked, so the CC Sense details are taken from
the BQ27426 one instead, which is supposedly the same silicon with an
external shunt.

Also the CC Sense value, which is just documented as "F4" (as in 4 bytes
float) is actually in a proprietary floating point format, so instead of
trying to decode, just swap the known sign bit as documented in the E2E
forum post.

Link: https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1215460/bq27427evm-misbehaving-stateofcharge
Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
This commit is contained in:
Fabio Baltieri 2023-07-23 20:43:55 +01:00 • committed by Carles Cufí
commit 72a2b81f75
1 changed files with 78 additions and 0 deletions
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78
drivers/sensor/bq274xx/bq274xx.c
View file

@ -52,8 +52,13 @@ LOG_MODULE_REGISTER(bq274xx, CONFIG_SENSOR_LOG_LEVEL);
/* Config update mode flag */
#define BQ27XXX_FLAG_CFGUP BIT(4)
/* BQ27427 CC Gain */
#define BQ27427_CC_GAIN BQ274XX_EXT_BLKDAT(5)
#define BQ27427_CC_GAIN_SIGN_BIT BIT(7)
/* Subclasses */
#define BQ274XX_SUBCLASS_82 82
#define BQ274XX_SUBCLASS_105 105
static const struct bq274xx_regs bq27421_regs = {
.dm_design_capacity = 10,
@ -248,6 +253,72 @@ static int bq274xx_mode_cfgupdate(const struct device *dev, bool enabled)
return 0;
}
/*
* BQ27427 needs the CC Gain polarity swapped from the ROM value.
* The details are currently only documented in the TI E2E support forum:
* https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1215460/bq27427evm-misbehaving-stateofcharge
*/
static int bq27427_ccgain_quirk(const struct device *dev)
{
const struct bq274xx_config *const config = dev->config;
int ret;
uint8_t val, checksum;
ret = i2c_reg_write_byte_dt(&config->i2c, BQ274XX_EXT_DATA_CLASS,
BQ274XX_SUBCLASS_105);
if (ret < 0) {
LOG_ERR("Failed to update state subclass");
return -EIO;
}
ret = i2c_reg_write_byte_dt(&config->i2c, BQ274XX_EXT_DATA_BLOCK, 0x00);
if (ret < 0) {
LOG_ERR("Failed to update block offset");
return -EIO;
}
k_sleep(BQ274XX_SUBCLASS_DELAY);
ret = i2c_reg_read_byte_dt(&config->i2c, BQ27427_CC_GAIN, &val);
if (ret < 0) {
LOG_ERR("Failed to read ccgain");
return -EIO;
}
if (!(val & BQ27427_CC_GAIN_SIGN_BIT)) {
LOG_DBG("bq27427 quirk already applied");
return 0;
}
ret = i2c_reg_read_byte_dt(&config->i2c, BQ274XX_EXT_CHECKSUM, &checksum);
if (ret < 0) {
LOG_ERR("Failed to read block checksum");
return -EIO;
}
/* Flip the sign bit on both value and checksum. */
val ^= BQ27427_CC_GAIN_SIGN_BIT;
checksum ^= BQ27427_CC_GAIN_SIGN_BIT;
LOG_DBG("bq27427: val=%02x checksum=%02x", val, checksum);
ret = i2c_reg_write_byte_dt(&config->i2c, BQ27427_CC_GAIN, val);
if (ret < 0) {
LOG_ERR("Failed to update ccgain");
return -EIO;
}
ret = i2c_reg_write_byte_dt(&config->i2c, BQ274XX_EXT_CHECKSUM, checksum);
if (ret < 0) {
LOG_ERR("Failed to update block checksum");
return -EIO;
}
k_sleep(BQ274XX_SUBCLASS_DELAY);
return 0;
}
static int bq274xx_gauge_configure(const struct device *dev)
{
const struct bq274xx_config *const config = dev->config;
@ -310,6 +381,13 @@ static int bq274xx_gauge_configure(const struct device *dev)
return ret;
}
if (data->regs == &bq27427_regs) {
ret = bq27427_ccgain_quirk(dev);
if (ret < 0) {
return ret;
}
}
ret = bq274xx_mode_cfgupdate(dev, false);
if (ret < 0) {
return ret;