power: pm8921-bms: remember soc between restarts
Currently the code does not have a mechanism to remember the soc
reported just before shutting down and upon restarting the new
soc reported is off from the previous soc value reported.
This change introduces
- a method to save soc in an unused coincell back register: ssbi address
0x107 is not used on 8921 and serves the purpose of storing the soc.
The driver reads this value and uses it to scale the reported soc.
- a method to detect that a battery was removed and perhaps replaced by a
different one. If the battery is found replaced the driver is notified
of the change and it disregards the soc value it read from the backup
register. The charger driver has a battery backed bit (force vref
therm) which it sets in its initialization sequence. Once set the
value remains between restarts, unless the battery is removed. The
default value of this bit is 0. Hence if a zero is detected before
writing to it, battery was removed between restarts - this mechanism
is used to notify the BMS to disregard the soc read from the backup
register.
Note that for this to work correctly the bootloader needs to be updated to
not overwrite register 0x107 upon restart.
CRs-Fixed: 370287
Change-Id: If7d098552d36eb27a396ee7d37f78d3629861f6e
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>
diff --git a/drivers/power/pm8921-bms.c b/drivers/power/pm8921-bms.c
index 73c042d..600913f 100644
--- a/drivers/power/pm8921-bms.c
+++ b/drivers/power/pm8921-bms.c
@@ -47,6 +47,8 @@
#define AMUX_TRIM_2 0x322
#define TEST_PROGRAM_REV 0x339
+#define TEMP_SOC_STORAGE 0x107
+
enum pmic_bms_interrupts {
PM8921_BMS_SBI_WRITE_OK,
PM8921_BMS_CC_THR,
@@ -134,8 +136,10 @@
struct timeval t;
int last_uuc_uah;
int enable_fcc_learning;
+ int shutdown_soc;
};
+static int shutdown_soc_invalid;
static struct pm8921_bms_chip *the_chip;
#define DEFAULT_RBATT_MOHMS 128
@@ -1455,6 +1459,71 @@
return soc;
}
+#define MAX_SHUTDOWN_ADJUST_SECONDS 1800
+static int adjust_for_shutdown_soc(struct pm8921_bms_chip *chip, int soc)
+{
+ struct timespec uptime;
+ int val;
+
+ /* value of zero means the shutdown soc should not be used */
+ if (chip->shutdown_soc == 0)
+ return soc;
+
+ if (shutdown_soc_invalid) {
+ chip->shutdown_soc = 0;
+ return soc;
+ }
+
+ do_posix_clock_monotonic_gettime(&uptime);
+
+ if (uptime.tv_sec >= MAX_SHUTDOWN_ADJUST_SECONDS) {
+ /*
+ * adjusted for a long time now, switch to reporting the
+ * calculated soc
+ */
+ chip->shutdown_soc = 0;
+ return soc;
+ }
+
+ val = ((MAX_SHUTDOWN_ADJUST_SECONDS - uptime.tv_sec)
+ * chip->shutdown_soc
+ + uptime.tv_sec * soc);
+ val /= MAX_SHUTDOWN_ADJUST_SECONDS;
+ pr_debug("shutdown_soc = %d, adj soc = %d, calc soc = %d\n",
+ chip->shutdown_soc, val, soc);
+
+ return val;
+}
+
+static void backup_soc(struct pm8921_bms_chip *chip, int last_soc)
+{
+ /* TODO: if 0x107 is free for all variants 8917, 8038 etc */
+ pm8xxx_writeb(the_chip->dev->parent, TEMP_SOC_STORAGE, last_soc);
+}
+
+static void read_shutdown_soc(struct pm8921_bms_chip *chip)
+{
+ int rc;
+ u8 temp;
+
+ rc = pm8xxx_readb(chip->dev->parent, TEMP_SOC_STORAGE, &temp);
+ if (rc)
+ pr_err("failed to read addr = %d %d\n", TEMP_SOC_STORAGE, rc);
+ else
+ chip->shutdown_soc = temp;
+
+ pr_debug("shutdown_soc = %d\n", chip->shutdown_soc);
+}
+
+void pm8921_bms_invalidate_shutdown_soc(void)
+{
+ pr_debug("Invalidating shutdown soc - the battery was removed\n");
+ shutdown_soc_invalid = 1;
+ if (the_chip)
+ the_chip->shutdown_soc = 0;
+}
+EXPORT_SYMBOL(pm8921_bms_invalidate_shutdown_soc);
+
/*
* Remaining Usable Charge = remaining_charge (charge at ocv instance)
* - coloumb counter charge
@@ -1469,6 +1538,7 @@
int remaining_charge_uah, soc;
int cc_uah;
int rbatt;
+ int shutdown_adjusted_soc;
calculate_soc_params(chip, raw, batt_temp, chargecycles,
&fcc_uah,
@@ -1534,9 +1604,12 @@
last_soc);
}
- pr_debug("Reported SOC = %u%%\n", last_soc);
- return last_soc;
+ shutdown_adjusted_soc = adjust_for_shutdown_soc(chip, last_soc);
+ backup_soc(chip, shutdown_adjusted_soc);
+
+ return shutdown_adjusted_soc;
}
+
#define MIN_DELTA_625_UV 1000
static void calib_hkadc(struct pm8921_bms_chip *chip)
{
@@ -2629,6 +2702,8 @@
goto free_irqs;
}
+ read_shutdown_soc(chip);
+
platform_set_drvdata(pdev, chip);
the_chip = chip;
create_debugfs_entries(chip);