针对高通BMS的研究 高通电量计
高通8064 8974 8926等pm芯片都集成了电量计，估计后续芯片都会一直存在，现在许多项目UI状态栏电池都有百分比显示，所以需要深入分析BMS有助于解决电量方面的BUG。
一： SOC（荷电状态）计算方法
名词：
FCC Full-charge capacity
UC Remaining capacityCC Coulumb counter
UUC Unusable capacity
RUC Remaining usable capacity // RUC=RC-CC-UUC
SoC State of charge
OCV Open circuit voltage
SOC=(RC-CC-UUC)/(FCC-UUC)
以下是各个变量的计算方法：
1：FCC：
在校准的电池profile中有定义,会随温度有变化；
static struct single_row_lut fcc_temp = {
.x = {-20, 0, 25, 40, 60},
.y = {3193, 3190, 3190, 3180, 3183},
.cols = 5
};2：RC: 开机通过开始获取的开路电压（ocv）来查表（电池校准的profile文件）计算百分比，来比对计算（电压与电荷量正比）；(ocv=vbatt+rbatt*i_ma)
内核计算方法：
static int calculate_remaining_charge_uah(struct pm8921_bms_chip *chip,
struct pm8921_soc_params *raw,
int fcc_uah, int batt_temp,
int chargecycles)
{
int ocv, pc, batt_temp_decidegc;
ocv = raw->last_good_ocv_uv;
batt_temp_decidegc = chip->last_ocv_temp_decidegc;
pc = calculate_pc(chip, ocv, batt_temp_decidegc, chargecycles);
pr_info("ocv = %d pc = %d\n", ocv, pc);
return (fcc_uah * pc) / 100;
}但是通常情况下开机使用计算RC的ocv是上次关机存下的百分比，反向查表算出的ocv；
现在我们做法是通过判断开机时的ocv与关机的ocv如果偏差太大，我们将采用开机ocv来计算RC，所以开机的ocv对开机的百分比影响非常大；
3:CC:pmic库伦计 ADC采样到的：
内核获取方法：
/**
* calculate_cc_uah -
* @chip: the bms chip pointer
* @cc: the cc reading from bms h/w
* @val: return value
* @coulumb_counter: adjusted coulumb counter for 100%
*
* RETURNS: in val pointer coulumb counter based charger in uAh
* (micro Amp hour)
*/
static void calculate_cc_uah(struct pm8921_bms_chip *chip, int cc, int *val)
{
int64_t cc_voltage_uv, cc_pvh, cc_uah;
cc_voltage_uv = cc;
pr_debug("cc = %d\n", cc);
cc_voltage_uv = cc_to_microvolt(chip, cc_voltage_uv);
cc_voltage_uv = pm8xxx_cc_adjust_for_gain(cc_voltage_uv);
pr_debug("cc_voltage_uv = %lld microvolts\n", cc_voltage_uv);
cc_pvh = ccmicrovolt_to_pvh(cc_voltage_uv);
pr_debug("cc_pvh = %lld pico_volt_hour\n", cc_pvh);
cc_uah = div_s64(cc_pvh, chip->r_sense_uohm);
*val = cc_uah;
}4:UUC:计算方法和UC一致，但是rbatt是动态变化的，会复杂点；
static int calculate_termination_uuc(struct pm8921_bms_chip *chip,
int batt_temp, int chargecycles,
int fcc_uah, int i_ma,
int *ret_pc_unusable)
{
int unusable_uv, pc_unusable, uuc;
int i = 0;
int ocv_mv;
int batt_temp_degc = batt_temp / 10;
int rbatt_mohm;
int delta_uv;
int prev_delta_uv = 0;
int prev_rbatt_mohm = 0;
int prev_ocv_mv = 0;
int uuc_rbatt_uv;
for (i = 0; i <= 100; i++) {
ocv_mv = interpolate_ocv(chip->pc_temp_ocv_lut,
batt_temp_degc, i);
rbatt_mohm = get_rbatt(chip, i, batt_temp);
unusable_uv = (rbatt_mohm * i_ma) + (chip->v_cutoff * 1000);
delta_uv = ocv_mv * 1000 - unusable_uv;
pr_debug("soc = %d ocv = %d rbat = %d u_uv = %d delta_v = %d\n",
i, ocv_mv, rbatt_mohm, unusable_uv, delta_uv);
if (delta_uv > 0)
break;
prev_delta_uv = delta_uv;
prev_rbatt_mohm = rbatt_mohm;
prev_ocv_mv = ocv_mv;
}
uuc_rbatt_uv = linear_interpolate(rbatt_mohm, delta_uv,
prev_rbatt_mohm, prev_delta_uv,
0);
unusable_uv = (uuc_rbatt_uv * i_ma) + (chip->v_cutoff * 1000);
pc_unusable = calculate_pc(chip, unusable_uv, batt_temp, chargecycles);
uuc = (fcc_uah * pc_unusable) / 100;
pr_debug("For i_ma = %d, unusable_rbatt = %d unusable_uv = %d unusable_pc = %d uuc = %d\n",
i_ma, uuc_rbatt_uv, unusable_uv,
pc_unusable, uuc);
*ret_pc_unusable = pc_unusable;
return uuc;
}高通的这套BMS算法运行起来由于ocv的校准和温度等等原因，会有一定的偏差，高通还有一套通过校准OCV来估算SOC（简称soc_est）的机制，下面就是使用这套来校准SOC；
二：校准SOC
高通算法通过对soc与soc_est比较计算出ocv的差值，来改变last_ocv_uv的值，主要是改变RC，重新计算soc，将会使得soc与soc_est越来越接近，越来越准；
ocv在以下2种情况会被改变：
1：系统睡眠唤醒期间,cov被更新，库仑计RST；
2：低电进入adjust_soc()方法调节；在高通8064平台由于电量计对大电流计算不准确,一直亮屏的情况（没有经历睡眠唤醒的ocv更新与CC RST）会导致关机电压到达3.74V。要想解决这个问题必须使得校准SOC可以正常工作。但是当满电时开机就会记录ocv的值偏高，导致快要低电时不能很好的校准soc。所以有必要在马上进入低电（15%）时做一次模拟开机一次（电量计RERST CC=0从soc找出ocv ）使得last_ocv_uv降下来，才可以完美发挥adjust_soc的作用，使得关机电压能一直能到3.4V左右。
<6>[ 7796.038269] read_soc_params_raw: 333333333 last_good_ocv_uv= 3777000uV
<6>[ 7796.038360] read_soc_params_raw: last_good_ocv_raw= 0x943f, last_good_ocv_uv= 3777000uV
<6>[ 7796.038543] calculate_soc_params: FCC = 3190000uAh batt_temp = 300, cycles = 0
<6>[ 7796.038635] calculate_remaining_charge_uah: ocv = 3777000 pc = 35
<6>[ 7796.038665] calculate_soc_params: RC = 1116500uAh
<6>[ 7796.038726] calculate_soc_params: cc_uah = 394979uAh raw->cc = 5764312
<6>[ 7796.038818] calculate_state_of_charge: RUC(RC-CC-UUC) = 657721uAh RC = 1116500uAh CC= 394979uAh UUC= 63800uAh FCC= 3190000uAh SOC(RUC/FCC-UUC) =21
adjust_soc方法：
static int last_soc_est = -EINVAL;
static int adjust_soc(struct pm8921_bms_chip *chip, int soc,
int batt_temp, int chargecycles,
int rbatt, int fcc_uah, int uuc_uah, int cc_uah)
{
int ibat_ua = 0, vbat_uv = 0;
int ocv_est_uv = 0, soc_est = 0, pc_est = 0, pc = 0;
int delta_ocv_uv = 0;
int n = 0;
int rc_new_uah = 0;
int pc_new = 0;
int soc_new = 0;
int m = 0;
int rc = 0;
int delta_ocv_uv_limit = 0;
int correction_limit_uv = 0;
rc = pm8921_bms_get_simultaneous_battery_voltage_and_current(
&ibat_ua,
&vbat_uv);
if (rc < 0) {
pr_err("simultaneous vbat ibat failed err = %d\n", rc);
goto out;
}
very_low_voltage_check(chip, ibat_ua, vbat_uv);
if (chip->low_voltage_detect &&
wake_lock_active(&chip->low_voltage_wake_lock)) {
if (is_voltage_below_cutoff_window(chip, ibat_ua, vbat_uv)) {
soc = 0;
pr_info("Voltage below cutoff, setting soc to 0\n");
goto out;
}
}
delta_ocv_uv_limit = DIV_ROUND_CLOSEST(ibat_ua, 1000);
ocv_est_uv = vbat_uv + (ibat_ua * rbatt)/1000;
calc_current_max(chip, ocv_est_uv, rbatt);
pc_est = calculate_pc(chip, ocv_est_uv, batt_temp, last_chargecycles);
soc_est = div_s64((s64)fcc_uah * pc_est - uuc_uah*100,
(s64)fcc_uah - uuc_uah);
soc_est = bound_soc(soc_est);
/* never adjust during bms reset mode */
if (bms_reset) {
pr_debug("bms reset mode, SOC adjustment skipped\n");
goto out;
}
if (ibat_ua < 0 && pm8921_is_batfet_closed()) {
soc = charging_adjustments(chip, soc, vbat_uv, ibat_ua,
batt_temp, chargecycles,
fcc_uah, cc_uah, uuc_uah);
goto out;
}
/*
* do not adjust
* if soc_est is same as what bms calculated
* OR if soc_est > 15
* OR if soc it is above 90 because we might pull it low
* and cause a bad user experience
*/
if (soc_est == soc
|| soc_est > 15
|| soc >= 90)
goto out;
if (last_soc_est == -EINVAL)
last_soc_est = soc;
n = min(200, max(1 , soc + soc_est + last_soc_est));
/* remember the last soc_est in last_soc_est */
last_soc_est = soc_est;
pc = calculate_pc(chip, chip->last_ocv_uv,
chip->last_ocv_temp_decidegc, last_chargecycles);
if (pc > 0) {
pc_new = calculate_pc(chip, chip->last_ocv_uv - (++m * 1000),
chip->last_ocv_temp_decidegc,
last_chargecycles);
while (pc_new == pc) {
/* start taking 10mV steps */
m = m + 10;
pc_new = calculate_pc(chip,
chip->last_ocv_uv - (m * 1000),
chip->last_ocv_temp_decidegc,
last_chargecycles);
}
} else {
/*
* pc is already at the lowest point,
* assume 1 millivolt translates to 1% pc
*/
pc = 1;
pc_new = 0;
m = 1;
}
delta_ocv_uv = div_s64((soc - soc_est) * (s64)m * 1000,
n * (pc - pc_new));
if (abs(delta_ocv_uv) > delta_ocv_uv_limit) {
pr_debug("limiting delta ocv %d limit = %d\n", delta_ocv_uv,
delta_ocv_uv_limit);
if (delta_ocv_uv > 0)
delta_ocv_uv = delta_ocv_uv_limit;
else
delta_ocv_uv = -1 * delta_ocv_uv_limit;
pr_debug("new delta ocv = %d\n", delta_ocv_uv);
}
if (wake_lock_active(&chip->low_voltage_wake_lock)) {
pr_debug("Low Voltage, apply only ibat limited corrections\n");
goto skip_limiting_corrections;
}
if (chip->last_ocv_uv > 3800000)
correction_limit_uv = the_chip->high_ocv_correction_limit_uv;
else
correction_limit_uv = the_chip->low_ocv_correction_limit_uv;
if (abs(delta_ocv_uv) > correction_limit_uv) {
pr_debug("limiting delta ocv %d limit = %d\n", delta_ocv_uv,
correction_limit_uv);
if (delta_ocv_uv > 0)
delta_ocv_uv = correction_limit_uv;
else
delta_ocv_uv = -1 * correction_limit_uv;
pr_debug("new delta ocv = %d\n", delta_ocv_uv);
}
skip_limiting_corrections:
chip->last_ocv_uv -= delta_ocv_uv;
if (chip->last_ocv_uv >= chip->max_voltage_uv)
chip->last_ocv_uv = chip->max_voltage_uv;
/* calculate the soc based on this new ocv */
pc_new = calculate_pc(chip, chip->last_ocv_uv,
chip->last_ocv_temp_decidegc, last_chargecycles);
rc_new_uah = (fcc_uah * pc_new) / 100;
soc_new = (rc_new_uah - cc_uah - uuc_uah)*100 / (fcc_uah - uuc_uah);
soc_new = bound_soc(soc_new);
/*
* if soc_new is ZERO force it higher so that phone doesnt report soc=0
* soc = 0 should happen only when soc_est == 0
*/
if (soc_new == 0 && soc_est >= the_chip->hold_soc_est)
soc_new = 1;
soc = soc_new;
out:
pr_debug("ibat_ua = %d, vbat_uv = %d, ocv_est_uv = %d, pc_est = %d, "
"soc_est = %d, n = %d, delta_ocv_uv = %d, last_ocv_uv = %d, "
"pc_new = %d, soc_new = %d, rbatt = %d, m = %d\n",
ibat_ua, vbat_uv, ocv_est_uv, pc_est,
soc_est, n, delta_ocv_uv, chip->last_ocv_uv,
pc_new, soc_new, rbatt, m);
return soc;
}