ln9310: Stronger workaround to prevent SCOUT overvoltage at startup

This improved workaround (compared to the previous 2520279) moves
the CFLY precharge step out of the ln9310's internal startup
sequence and implements it using I2C commands sent by the EC just before
the I2C command that triggers the ln9310 startup.  The workaround
additionally modifies the ln9310's internal startup sequence to use
the precharged CFLY capacitors as decoupling of an internal node
during the startup sequence which should help prevent an OV glitch
from appearing on the LN9310 output even if the internal level
shifter on SW1 glitches and pulls up on the C1PA/B nodes.

BRANCH=Trogdor
BUG=b:185308433
TEST=Should not break the current boot flow, i.e. power-up and
power-down (using long-press of the power button) should function
similar to before this change.  Testing the efficacy at preventing
the SCOUT overvoltage glitch must be done with LN9310 parts screened
out at wafer test that have a higher likelihood of exhibiting the
glitch at the SCOUT output.  With these parts, startup should be
observed with a scope probe monitoring LN9310 SCOUT for overvoltagee.

Change-Id: I216991f950196225cabbbfdaa2333f1650f7f4fa
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2837531
Reviewed-by: Alexandru M Stan <amstan@chromium.org>
Reviewed-by: Wai-Hong Tam <waihong@google.com>
Tested-by: John Crossley <crossley@lionsemi.corp-partner.google.com>
Commit-Queue: John Crossley <crossley@lionsemi.corp-partner.google.com>

4 files changed, 277 insertions, 38 deletions

diff --git a/board/homestar/board.c b/board/homestar/board.c
index ce13ee1076..657b547c5f 100644
--- a/board/homestar/board.c
+++ b/board/homestar/board.c
@@ -439,6 +439,7 @@ DECLARE_HOOK(HOOK_CHIPSET_RESUME, board_chipset_resume, HOOK_PRIO_DEFAULT);
 void board_set_switchcap_power(int enable)
 {
 	gpio_set_level(GPIO_SWITCHCAP_ON_L, !enable);
+	ln9310_software_enable(enable);
 }
 
 int board_is_switchcap_enabled(void)
diff --git a/board/lazor/switchcap.c b/board/lazor/switchcap.c
index 3d5255791c..6cb5106efb 100644
--- a/board/lazor/switchcap.c
+++ b/board/lazor/switchcap.c
@@ -105,10 +105,12 @@ DECLARE_HOOK(HOOK_INIT, switchcap_init, HOOK_PRIO_DEFAULT);
 
 void board_set_switchcap_power(int enable)
 {
-	if (board_has_ln9310())
+	if (board_has_ln9310()) {
 		gpio_set_level(GPIO_SWITCHCAP_ON_L, !enable);
-	else
+		ln9310_software_enable(enable);
+	} else {
 		gpio_set_level(GPIO_SWITCHCAP_ON, enable);
+	}
 }
 
 int board_is_switchcap_enabled(void)
diff --git a/driver/ln9310.c b/driver/ln9310.c
index 31c6dbca7a..d339c228a2 100644
--- a/driver/ln9310.c
+++ b/driver/ln9310.c
@@ -18,6 +18,7 @@
 #define CPRINTS(format, args...) cprints(CC_I2C, format, ## args)
 
 static int power_good;
+static int startup_workaround_required;
 
 int ln9310_power_good(void)
 {
@@ -119,22 +120,25 @@ static int ln9310_update_startup_seq(void)
 {
 	CPRINTS("LN9310 update startup sequence");
 
-	/* Startup sequence instruction swap */
+	/*
+	 * Startup sequence instruction swap to hold Cfly
+	 * bottom plate low during startup
+	 */
 	field_update8(LN9310_REG_LION_CTRL,
 		      LN9310_LION_CTRL_MASK,
-		      LN9310_LION_CTRL_UNLOCK);
+		      LN9310_LION_CTRL_UNLOCK_AND_EN_TM);
 
 	field_update8(LN9310_REG_SWAP_CTRL_0,
 		      0xff,
-		      0x3f);
+		      0x52);
 
 	field_update8(LN9310_REG_SWAP_CTRL_1,
 		      0xff,
-		      0x51);
+		      0x54);
 
 	field_update8(LN9310_REG_SWAP_CTRL_2,
 		      0xff,
-		      0x19);
+		      0xCC);
 
 	field_update8(LN9310_REG_SWAP_CTRL_3,
 		      0xff,
@@ -180,7 +184,7 @@ static int ln9310_init_3to1(void)
 		      LN9310_PWR_OP_MODE_MASK,
 		      LN9310_PWR_OP_MODE_SWITCH31);
 
-	/* 3S lower bounde delta configurations */
+	/* 3S lower bound delta configurations */
 	field_update8(LN9310_REG_LB_CTRL,
 		      LN9310_LB_DELTA_MASK,
 		      LN9310_LB_DELTA_3S);
@@ -217,7 +221,7 @@ static int ln9310_init_2to1(void)
 		      LN9310_PWR_OP_MODE_MASK,
 		      LN9310_PWR_OP_MODE_SWITCH21);
 
-	/* 2S lower bounde delta configurations */
+	/* 2S lower bound delta configurations */
 	field_update8(LN9310_REG_LB_CTRL,
 		      LN9310_LB_DELTA_MASK,
 		      LN9310_LB_DELTA_2S);
@@ -240,7 +244,7 @@ static int ln9310_update_infet(void)
 
 	field_update8(LN9310_REG_LION_CTRL,
 		      LN9310_LION_CTRL_MASK,
-		      LN9310_LION_CTRL_UNLOCK);
+		      LN9310_LION_CTRL_UNLOCK_AND_EN_TM);
 
 	/* Update Infet register settings */
 	field_update8(LN9310_REG_CFG_5,
@@ -268,11 +272,107 @@ static int ln9310_update_infet(void)
 	return EC_SUCCESS;
 }
 
+static int ln9310_precharge_cfly(uint64_t *precharge_timeout)
+{
+	int status = 0;
+	CPRINTS("LN9310 precharge cfly");
+
+	/* Unlock registers and enable test mode */
+	status |= field_update8(LN9310_REG_LION_CTRL,
+			LN9310_LION_CTRL_MASK,
+			LN9310_LION_CTRL_UNLOCK_AND_EN_TM);
+
+	/* disable test mode overrides */
+	status |= field_update8(LN9310_REG_FORCE_SC21_CTRL_2,
+			LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_MASK,
+			LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_OFF);
+
+	/* Configure test mode target values for precharge ckts.  */
+	status |= field_update8(LN9310_REG_FORCE_SC21_CTRL_1,
+			LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_MASK,
+			LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_ON);
+
+	/* Force SCOUT precharge/predischarge overrides */
+	status |= field_update8(LN9310_REG_TEST_MODE_CTRL,
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_MASK |
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_MASK,
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_ON |
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_ON);
+
+	/* Force enable CFLY precharge overrides */
+	status |= field_update8(LN9310_REG_FORCE_SC21_CTRL_2,
+			LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_MASK,
+			LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_ON);
+
+	/* delay long enough to ensure CFLY has time to fully precharge */
+	usleep(LN9310_CFLY_PRECHARGE_DELAY);
+
+	/* locking and leaving test mode will stop CFLY precharge */
+	*precharge_timeout = get_time().val + LN9310_CFLY_PRECHARGE_TIMEOUT;
+	status |= field_update8(LN9310_REG_LION_CTRL,
+			LN9310_LION_CTRL_MASK,
+			LN9310_LION_CTRL_LOCK);
+
+	return status;
+}
+
+static int ln9310_precharge_cfly_reset(void)
+{
+	int status = 0;
+	CPRINTS("LN9310 precharge cfly reset");
+
+	/* set known initial state for config bits related to cfly precharge */
+	status |= field_update8(LN9310_REG_LION_CTRL,
+		LN9310_LION_CTRL_MASK,
+		LN9310_LION_CTRL_UNLOCK);
+
+	/* Force off SCOUT precharge/predischarge overrides */
+	status |= field_update8(LN9310_REG_TEST_MODE_CTRL,
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_MASK |
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_MASK,
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_OFF |
+			LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_OFF);
+
+	/* disable test mode overrides */
+	status |= field_update8(LN9310_REG_FORCE_SC21_CTRL_2,
+			LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_MASK,
+			LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_OFF);
+
+	/* disable CFLY and SC_OUT precharge control  */
+	status |= field_update8(LN9310_REG_FORCE_SC21_CTRL_1,
+			LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_MASK,
+			LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_OFF);
+
+	status |= field_update8(LN9310_REG_LION_CTRL,
+			LN9310_LION_CTRL_MASK,
+			LN9310_LION_CTRL_LOCK);
+
+	return status;
+}
+
 void ln9310_init(void)
 {
-	int status, val;
+	int status, val, chip_revision;
 	enum battery_cell_type batt;
 
+	/* Make sure initial state of LN9310 is STANDBY (i.e. output is off)  */
+	field_update8(LN9310_REG_STARTUP_CTRL,
+				LN9310_STARTUP_STANDBY_EN,
+				1);
+
+	/*
+	 * LN9310 software startup is only required for earlier silicon revs.
+	 * LN9310 hardware revisions after LN9310_BC_STS_C_CHIP_REV_FIXED
+	 * should not use the software startup sequence.
+	 */
+	status = raw_read8(LN9310_REG_BC_STS_C, &val);
+	if (status) {
+		CPRINTS("LN9310 reading BC_STS_C failed");
+		return;
+	}
+	chip_revision = val && LN9310_BC_STS_C_CHIP_REV_MASK;
+	startup_workaround_required = chip_revision < LN9310_BC_STS_C_CHIP_REV_FIXED;
+
 	/* Update INFET configuration  */
 	status = ln9310_update_infet();
 
@@ -312,11 +412,12 @@ void ln9310_init(void)
 	usleep(LN9310_CDC_DELAY);
 	CPRINTS("LN9310 OP_MODE Update method: Self-sync");
 
-	/* Update Startup sequence */
-	status = ln9310_update_startup_seq();
-
-	if (status != EC_SUCCESS)
-		return;
+	if (startup_workaround_required) {
+		/* Update Startup sequence */
+		status = ln9310_update_startup_seq();
+		if (status != EC_SUCCESS)
+			return;
+	}
 
 	batt = board_get_battery_cell_type();
 	if (batt == BATTERY_CELL_TYPE_3S) {
@@ -333,20 +434,124 @@ void ln9310_init(void)
 
 	/* Unmask the MODE change interrupt */
 	field_update8(LN9310_REG_INT1_MSK,
-		      LN9310_INT1_MODE,
-		      0);
+			LN9310_INT1_MODE,
+			0);
+}
 
+void ln9310_software_enable(int enable)
+{
+	int status, val, retry_count;
+	uint64_t precharge_timeout;
+	bool ln9310_init_completed = false;
+
+	/*
+	 * LN9310 startup requires (nEN=0 AND STANDBY_EN=0) where nEN is a pin
+	 * and STANDBY_EN is a register bit. Previous EC firmware set
+	 * STANDBY_EN=1 in ln9310_init and toggled nEN to startup/shutdown. This
+	 * function implements an alternate software (i.e. controlled by EC
+	 * through I2C commands) startup sequence so one option is to set nEN=1
+	 * and just used ln9310_software_enable to startup/shutdown.
+	 * ln9310_software_enable can also be used in conjunction w/ the nEN pin
+	 * (in case nEN pin is desired as visible signal ) as follows:
+	 *
+	 * Initial battery insertion:
+	 * nEN=1
+	 * ln9310_init() - initial condition is STANDBY_EN=1
+	 *
+	 * Power up LN9310:
+	 * nEN=0 - STANDBY_EN should be 1 so this doesn't trigger startup
+	 * ln9310_software_enable(1) - triggers alternate software-based startup
+	 *
+	 * Power down LN9310:
+	 * nEN=1 - shutdown LN9310 (shutdown seq. does not require modification)
+	 * ln9310_software_enable(0) - reset LN9310 register to state necessary
+	 *                             for subsequent startups
+	 */
 	/* Dummy clear all interrupts */
 	status = raw_read8(LN9310_REG_INT1, &val);
 	if (status) {
 		CPRINTS("LN9310 reading INT1 failed");
 		return;
 	}
-
-	/* Clear the STANDBY_EN bit */
-	field_update8(LN9310_REG_STARTUP_CTRL,
-		      LN9310_STARTUP_STANDBY_EN,
-		      0);
-
 	CPRINTS("LN9310 cleared interrupts: 0x%x", val);
-}
+
+	if (startup_workaround_required) {
+		if (enable) {
+			/*
+			* Software modification of LN9310 startup sequence w/ retry
+			* loop.
+			*
+			* (1) Clear interrupts
+			* (2) Precharge Cfly w/ overrides of internal LN9310 signals
+			* (3) disable overrides -> stop precharging Cfly
+			* (4.1) if < 100 ms elapsed since (2) -> trigger LN9310 internal
+			*                                        startup seq. 
+			* (4.2) else -> abort and optionally retry from step 2
+			*/
+			retry_count = 0;
+			while (!ln9310_init_completed && retry_count < LN9310_INIT_RETRY_COUNT) {
+				/* Precharge CFLY before starting up */
+				status = ln9310_precharge_cfly(&precharge_timeout);
+				if (status != EC_SUCCESS) {
+					CPRINTS("LN9310 failed to run Cfly precharge sequence");
+					status = ln9310_precharge_cfly_reset();
+					retry_count++;
+					continue;
+				}
+
+				/*
+				* Only start the SC if the cfly precharge
+				* hasn't timed out (i.e. ended too long ago)
+				*/
+				if (get_time().val < precharge_timeout) {
+					/* Clear the STANDBY_EN bit to enable the SC */
+					field_update8(LN9310_REG_STARTUP_CTRL,
+							LN9310_STARTUP_STANDBY_EN,
+							0);
+					if (get_time().val > precharge_timeout ) {
+						/*
+						* if timed out during previous I2C command, abort 
+						* startup attempt
+						*/
+						field_update8(LN9310_REG_STARTUP_CTRL,
+							LN9310_STARTUP_STANDBY_EN,
+							1);
+					} else {
+						/* all other paths should reattempt startup  */
+						ln9310_init_completed = true;
+					}
+				}
+				/* Reset to known state for config bits related to cfly precharge */
+				ln9310_precharge_cfly_reset();
+				retry_count++;
+			}
+
+			if (!ln9310_init_completed) {
+				CPRINTS("LN9310 failed to start after %d retry attempts",
+						retry_count);
+			}
+		} else {
+			/*
+			* Internal LN9310 shutdown sequence is ok as is, so just reset
+			* the state to prepare for subsequent startup sequences.
+			*
+			* (1) set STANDBY_EN=1 to be sure the part turns off even if nEN=0
+			* (2) reset cfly precharge related registers to known initial state
+			*/
+			field_update8(LN9310_REG_STARTUP_CTRL,
+					LN9310_STARTUP_STANDBY_EN,
+					1);
+
+			ln9310_precharge_cfly_reset();
+		}
+	} else {
+		/*
+		* for newer LN9310 revsisions, the startup workaround is not required
+		* so the STANDBY_EN bit can just be set directly
+		*/
+		field_update8(LN9310_REG_STARTUP_CTRL,
+					LN9310_STARTUP_STANDBY_EN,
+					!enable);
+	}
+	return;
+}
\ No newline at end of file
diff --git a/include/driver/ln9310.h b/include/driver/ln9310.h
index 07cff8ba97..e4bd0bc7e0 100644
--- a/include/driver/ln9310.h
+++ b/include/driver/ln9310.h
@@ -66,14 +66,14 @@
 #define LN9310_REG_SYS_CTRL		0x1e
 
 #define LN9310_REG_STARTUP_CTRL			0x1f
-#define LN9310_STARTUP_STANDBY_EN		BIT(0)
+#define LN9310_STARTUP_STANDBY_EN				BIT(0)
 #define LN9310_STARTUP_SELECT_EXT_5V_FOR_VDR	BIT(3)
 
 #define LN9310_REG_IIN_CTRL		0x20
 #define LN9310_REG_VIN_CTRL		0x21
 
 #define LN9310_REG_TRACK_CTRL		0x22
-#define LN9310_TRACK_INFET_OUT_SWITCH_OK_EN		BIT(7)
+#define LN9310_TRACK_INFET_OUT_SWITCH_OK_EN			BIT(7)
 #define LN9310_TRACK_INFET_OUT_SWITCH_OK_CFG2		BIT(6)
 #define LN9310_TRACK_INFET_OUT_SWITCH_OK_CFG1		BIT(5)
 #define LN9310_TRACK_INFET_OUT_SWITCH_OK_CFG0		BIT(4)
@@ -93,8 +93,8 @@
 #define LN9310_REG_RECOVERY_CTRL	0x25
 
 #define LN9310_REG_LB_CTRL		0x26
-#define LN9310_LB_MIN_FREQ_EN		BIT(2)
-#define LN9310_LB_DELTA_MASK		0x38
+#define LN9310_LB_MIN_FREQ_EN	BIT(2)
+#define LN9310_LB_DELTA_MASK	0x38
 #define LN9310_LB_DELTA_2S		0x20
 #define LN9310_LB_DELTA_3S		0x20
 
@@ -130,23 +130,24 @@
 
 #define LN9310_REG_SC_DITHER_CTRL	0x2f
 
-#define LN9310_REG_LION_CTRL	0x30
-#define LN9310_LION_CTRL_MASK	0xFF
-#define LN9310_LION_CTRL_UNLOCK	0xAA
-#define LN9310_LION_CTRL_LOCK	0x00
+#define LN9310_REG_LION_CTRL				0x30
+#define LN9310_LION_CTRL_MASK				0xFF
+#define LN9310_LION_CTRL_UNLOCK_AND_EN_TM	0xAA
+#define LN9310_LION_CTRL_UNLOCK				0x5B
+#define LN9310_LION_CTRL_LOCK				0x00
 
 #define LN9310_REG_CFG_0	0x3C
-#define LN9310_CFG_0_LS_HELPER_IDLE_MSK_MASK		0x20
+#define LN9310_CFG_0_LS_HELPER_IDLE_MSK_MASK	0x20
 #define LN9310_CFG_0_LS_HELPER_IDLE_MSK_ON		0x20
 
 #define LN9310_REG_CFG_4	0x40
 #define LN9310_CFG_4_SC_OUT_PRECHARGE_EN_TIME_CFG		BIT(2)
-#define LN9310_CFG_4_SW1_VGS_SHORT_EN_MSK			BIT(3)
+#define LN9310_CFG_4_SW1_VGS_SHORT_EN_MSK				BIT(3)
 #define LN9310_CFG_4_SC_OUT_PRECHARGE_EN_TIME_CFG_MASK 	0x04
-#define LN9310_CFG_4_SW1_VGS_SHORT_EN_MSK_MASK		0x08
+#define LN9310_CFG_4_SW1_VGS_SHORT_EN_MSK_MASK			0x08
 #define LN9310_CFG_4_BSTH_BSTL_HIGH_ROUT_CFG_MASK		0xC0
 #define LN9310_CFG_4_SC_OUT_PRECHARGE_EN_TIME_CFG_ON 	0x04
-#define LN9310_CFG_4_SW1_VGS_SHORT_EN_MSK_OFF		0x00
+#define LN9310_CFG_4_SW1_VGS_SHORT_EN_MSK_OFF			0x00
 #define LN9310_CFG_4_BSTH_BSTL_HIGH_ROUT_CFG_LOWEST		0x00
 
 #define LN9310_REG_CFG_5	0x41
@@ -155,6 +156,24 @@
 #define LN9310_CFG_5_INFET_CP_PD_BIAS_CFG_MASK		0x30
 #define LN9310_CFG_5_INFET_CP_PD_BIAS_CFG_LOWEST	0x00
 
+#define LN9310_REG_TEST_MODE_CTRL	0x46
+#define LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_MASK		0x40
+#define LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_ON			0x40
+#define LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PRECHARGE_OFF		0x00
+#define LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_MASK	0x20
+#define LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_ON		0x20
+#define LN9310_TEST_MODE_CTRL_FORCE_SC_OUT_PREDISCHARGE_OFF		0x00
+
+#define LN9310_REG_FORCE_SC21_CTRL_1	0x49
+#define LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_MASK	0xFF
+#define LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_ON	0x59
+#define LN9310_FORCE_SC21_CTRL_1_TM_SC_OUT_CFLY_PRECHARGE_OFF	0x40
+
+#define LN9310_REG_FORCE_SC21_CTRL_2	0x4A
+#define LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_MASK		0x80
+#define LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_ON		0x80
+#define LN9310_FORCE_SC21_CTRL_2_FORCE_SW_CTRL_REQ_OFF		0x00
+
 #define LN9310_REG_SWAP_CTRL_0	0x58
 #define LN9310_REG_SWAP_CTRL_1	0x59
 #define LN9310_REG_SWAP_CTRL_2	0x5A
@@ -164,8 +183,17 @@
 #define LN9310_BC_STS_B_INFET_OUT_SWITCH_OK		BIT(5)
 #define LN9310_BC_STS_B_INFET_OUT_SWITCH_OK_MASK	0x20
 
+#define LN9310_REG_BC_STS_C				0x52
+#define LN9310_BC_STS_C_CHIP_REV_MASK	0xF0
+#define LN9310_BC_STS_C_CHIP_REV_FIXED	0x40
+
 /* LN9310 Timing definition */
-#define LN9310_CDC_DELAY 120	/* 120us */
+#define LN9310_CDC_DELAY 				120	/* 120us */
+#define LN9310_CFLY_PRECHARGE_DELAY 	(12*MSEC)
+#define LN9310_CFLY_PRECHARGE_TIMEOUT	(100*MSEC)
+
+/* LN9310 Driver Configuration */
+#define LN9310_INIT_RETRY_COUNT 3
 
 /* Define configuration of LN9310 part */
 struct ln9310_config_t {
@@ -179,6 +207,9 @@ extern const struct ln9310_config_t ln9310_config;
 /* Init the driver */
 void ln9310_init(void);
 
+/* Enable/disable the ln9310 output */
+void ln9310_software_enable(int enable);
+
 /* Interrupt handler */
 void ln9310_interrupt(enum gpio_signal signal);