针对高通BMS的研究 高通电量计

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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 capacity
CC     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
", 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
", 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
", cc_voltage_uv);
 cc_pvh = ccmicrovolt_to_pvh(cc_voltage_uv);
 pr_debug("cc_pvh = %lld pico_volt_hour
", 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
",
    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
",
     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：

</pre><p class="pa-1" style="line-height: 18px; font-size: 14px; padding-top: 0px; padding-bottom: 0px; margin-top: 0px; margin-bottom: 10px; color: rgb(68, 68, 68); font-family: 宋体;"><pre name="code" class="html"> 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
", 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
");



   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
");



  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
", 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
", delta_ocv_uv);



 }







 if (wake_lock_active(&chip->low_voltage_wake_lock)) {



  pr_debug("Low Voltage, apply only ibat limited corrections
");



  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
", 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
", 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
",



  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;



}