bd9995x: Disable IADP

This patch disables IADP immediately after the EC boots. We
observed noise on IADP/RESET pin causing SEL_ILIM_VAL to
randomly change. This seems the cause of b:35648317.

We enabled IADP to fix b:35647661 initially and also followed
the vendor's recommendation. However, the issue is only
reproducible on the particular board which was used for power
measurement and we did not see the issue on other boards with
IADP disabled.

Also the vendor assumed our EC doesn't control IBUS_LIM_SET
and ICC_LIM_SET. (I think they assumed like other thier customers
our EC controls ILIM by DAC connected to IADP/RESET pin.) If ILIM
is not set by EC and IADP is disabled, the system would brownout
because ILIM stays at 128mA. Therefore, it was (mistakenly)
recommended that our EC should keep IADP enabled.

Cros EC configures IBUS_LIM_SET and ICC_LIM_SET dynamically thus
the above concern does not apply.

We also found that we have too much noise on IADP/RESET pin. The
noise is not big enough to cause the chip to reset but it's big
enough to cause ILIM to fall in 128mA zone. We think this is why
the boards fail to boot from battery cutoff or no battery.
(Contrary to the vendor's explanation, it seems IADP/RESET pin
continusouly affects ILIM not only in the early chip power-up
period.)

BUG=b:35648317
BRANCH=none
TEST=Booted two Electro and two Snappy from 1) dead battery 2) no
battery 3) battery cutoff.

Change-Id: Ic675f1354b9ef222ceec8ce112b19713812d2752
Reviewed-on: https://chromium-review.googlesource.com/458676
Commit-Ready: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/driver/charger/bd9995x.c b/driver/charger/bd9995x.c
index af8b0cc082..d74e0cd635 100644
--- a/driver/charger/bd9995x.c
+++ b/driver/charger/bd9995x.c
@@ -798,6 +798,16 @@ static void bd9995x_init(void)
 	ch_raw_write16(BD9995X_CMD_CHGOP_SET2, reg,
 		       BD9995X_EXTENDED_COMMAND);
 
+	/*
+	 * We disable IADP (here before setting IBUS_LIM_SET and ICC_LIM_SET)
+	 * to prevent voltage on IADP/RESET pin from affecting SEL_ILIM_VAL.
+	 */
+	if (ch_raw_read16(BD9995X_CMD_VM_CTRL_SET, &reg,
+			  BD9995X_EXTENDED_COMMAND))
+		return;
+	reg &= ~BD9995X_CMD_VM_CTRL_SET_EXTIADPEN;
+	ch_raw_write16(BD9995X_CMD_VM_CTRL_SET, reg, BD9995X_EXTENDED_COMMAND);
+
 	/* Define battery charging profile */
 	bd9995x_battery_charging_profile_settings();