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Commit a7fe3740 authored by Xiaozhe Shi's avatar Xiaozhe Shi
Browse files

power: qpnp-bms: fake a more accurate OCV at end of charge 



When the bms is notified of end of charge, it fakes a high OCV in order
to report 100%. The high OCV used is the max voltage design for the
battery. However, that is not what should be used as the high OCV, since
the max voltage design corresponds to an over charged battery if used as
an OCV.

This can cause an issue with the correcting algorithm. When the BMS
driver finds that it needs to correct SOC downwards, it must do so by
lowering the OCV to correspond with a lower remaining charge. However,
since the battery profile does not start at max voltage design for 100%,
the BMS driver must correct about 25-30mV before it even starts
affecting SoC. This can create issues with meeting the cutoff voltage at
low SoCs.

Instead, look up the OCV for 100% charge and use that for the faked OCV.

Change-Id: I5ee3ab99098c3bf3354a4af792f2c5ff91aa60ed
Signed-off-by: default avatarXiaozhe Shi <xiaozhes@codeaurora.org>
parent 3625cd6e

drivers/power/qpnp-bms.c

+57 −58
Original line number Diff line number Diff line
@@ -923,14 +923,67 @@ static void reset_for_new_battery(struct qpnp_bms_chip *chip, int batt_temp) 
	}

}



#define SIGN(x) ((x) < 0 ? -1 : 1)

#define UV_PER_SPIN 50000

static int find_ocv_for_pc(struct qpnp_bms_chip *chip, int batt_temp, int pc)

{

	int new_pc;

	int batt_temp_degc = batt_temp / 10;

	int ocv_mv;

	int delta_mv = 5;

	int max_spin_count;

	int count = 0;

	int sign, new_sign;



	ocv_mv = interpolate_ocv(chip->pc_temp_ocv_lut, batt_temp_degc, pc);



	new_pc = interpolate_pc(chip->pc_temp_ocv_lut, batt_temp_degc, ocv_mv);

	pr_debug("test revlookup pc = %d for ocv = %d\n", new_pc, ocv_mv);

	max_spin_count = 1 + (chip->max_voltage_uv - chip->v_cutoff_uv)

						/ UV_PER_SPIN;

	sign = SIGN(pc - new_pc);



	while (abs(new_pc - pc) != 0 && count < max_spin_count) {

		/*

		 * If the newly interpolated pc is larger than the lookup pc,

		 * the ocv should be reduced and vice versa

		 */

		new_sign = SIGN(pc - new_pc);

		/*

		 * If the sign has changed, then we have passed the lookup pc.

		 * reduce the ocv step size to get finer results.

		 *

		 * If we have already reduced the ocv step size and still

		 * passed the lookup pc, just stop and use the current ocv.

		 * This can only happen if the batterydata profile is

		 * non-monotonic anyways.

		 */

		if (new_sign != sign) {

			if (delta_mv > 1)

				delta_mv = 1;

			else

				break;

		}

		sign = new_sign;



		ocv_mv = ocv_mv + delta_mv * sign;

		new_pc = interpolate_pc(chip->pc_temp_ocv_lut,

				batt_temp_degc, ocv_mv);

		pr_debug("test revlookup pc = %d for ocv = %d\n",

			new_pc, ocv_mv);

		count++;

	}



	return ocv_mv * 1000;

}



#define OCV_RAW_UNINITIALIZED	0xFFFF

#define MIN_OCV_UV		2000000

static int read_soc_params_raw(struct qpnp_bms_chip *chip,

				struct raw_soc_params *raw,

				int batt_temp)

{

	int warm_reset;

	int rc;

	int warm_reset, rc;



	mutex_lock(&chip->bms_output_lock);
@@ -978,8 +1031,8 @@ static int read_soc_params_raw(struct qpnp_bms_chip *chip, 
		chip->done_charging = false;

		/* if we just finished charging, reset CC and fake 100% */

		chip->ocv_reading_at_100 = raw->last_good_ocv_raw;

		chip->last_ocv_uv = chip->max_voltage_uv;

		raw->last_good_ocv_uv = chip->max_voltage_uv;

		chip->last_ocv_uv = find_ocv_for_pc(chip, batt_temp, 100);

		raw->last_good_ocv_uv = chip->last_ocv_uv;

		raw->cc = 0;

		raw->shdw_cc = 0;

		reset_cc(chip, CLEAR_CC | CLEAR_SHDW_CC);
@@ -1356,60 +1409,6 @@ static int find_pc_for_soc(struct qpnp_bms_chip *chip, 
	return pc;

}



#define SIGN(x) ((x) < 0 ? -1 : 1)

#define UV_PER_SPIN 50000

static int find_ocv_for_pc(struct qpnp_bms_chip *chip, int batt_temp, int pc)

{

	int new_pc;

	int batt_temp_degc = batt_temp / 10;

	int ocv_mv;

	int delta_mv = 5;

	int max_spin_count;

	int count = 0;

	int sign, new_sign;



	ocv_mv = interpolate_ocv(chip->pc_temp_ocv_lut, batt_temp_degc, pc);



	new_pc = interpolate_pc(chip->pc_temp_ocv_lut, batt_temp_degc, ocv_mv);

	pr_debug("test revlookup pc = %d for ocv = %d\n", new_pc, ocv_mv);

	max_spin_count = 1 + (chip->max_voltage_uv - chip->v_cutoff_uv)

						/ UV_PER_SPIN;

	sign = SIGN(pc - new_pc);



	while (abs(new_pc - pc) != 0 && count < max_spin_count) {

		/*

		 * If the newly interpolated pc is larger than the lookup pc,

		 * the ocv should be reduced and vice versa

		 */

		new_sign = SIGN(pc - new_pc);

		/*

		 * If the sign has changed, then we have passed the lookup pc.

		 * reduce the ocv step size to get finer results.

		 *

		 * If we have already reduced the ocv step size and still

		 * passed the lookup pc, just stop and use the current ocv.

		 * This can only happen if the batterydata profile is

		 * non-monotonic anyways.

		 */

		if (new_sign != sign) {

			if (delta_mv > 1)

				delta_mv = 1;

			else

				break;

		}

		sign = new_sign;



		ocv_mv = ocv_mv + delta_mv * sign;

		new_pc = interpolate_pc(chip->pc_temp_ocv_lut,

				batt_temp_degc, ocv_mv);

		pr_debug("test revlookup pc = %d for ocv = %d\n",

			new_pc, ocv_mv);

		count++;

	}



	return ocv_mv * 1000;

}



static int get_current_time(unsigned long *now_tm_sec)

{

	struct rtc_time tm;