cheza: Make chipset_reset do a warm reset

Make the chipset_reset function do a warm reset to match the
expectation of what AP-initiated reset does, which is also a
warm reset but triggered by PS_HOLD.

The warm reset is done by sending a low pulse to the PMIC
RESIN_L pin, which requires PMIC registers being reprogrammed
that makes it as a warm reset trigger.

If the PMIC registers not reprogrammed properly, it falls back
to do a cold reset power sequence. It is done by EC monitoring
the AP_RST_L signal, which is already one of the power signals.

BRANCH=none
BUG=b:117941911
TEST=Typed "apreset" just after "reboot" (PMIC registers not
programmed), checked the transition S0 -> S5 -> S0.
TEST=Typed "apreset" when AP booted into userspace (PMIC
registers programmed), checked a warm reset happened, AP_RST_L
toggled.

Change-Id: Ia1c5c7a8fd56a9e4867d4dd4c8bf2333c083c616
Signed-off-by: Wai-Hong Tam <waihong@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1330117
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>

1 files changed, 36 insertions, 6 deletions

diff --git a/power/sdm845.c b/power/sdm845.c
index 9fb4bcd141..837a54875d 100644
--- a/power/sdm845.c
+++ b/power/sdm845.c
@@ -37,7 +37,9 @@
 #define CPRINTS(format, args...) cprints(CC_CHIPSET, format, ## args)
 
 /* Masks for power signals */
-#define IN_POWER_GOOD POWER_SIGNAL_MASK(SDM845_POWER_GOOD)
+#define IN_POWER_GOOD		POWER_SIGNAL_MASK(SDM845_POWER_GOOD)
+#define IN_AP_RST_ASSERTED	POWER_SIGNAL_MASK(SDM845_AP_RST_ASSERTED)
+
 
 /* Long power key press to force shutdown */
 #define DELAY_FORCE_SHUTDOWN		(8 * SECOND)
@@ -67,6 +69,9 @@
 /* Wait for polling the AP on signal */
 #define PMIC_POWER_AP_WAIT		(1 * MSEC)
 
+/* The length of an issued low pulse to the PM845_RESIN_L signal */
+#define PMIC_RESIN_PULSE_LENGTH		(20 * MSEC)
+
 /* The timeout of the check if the system can boot AP */
 #define CAN_BOOT_AP_CHECK_TIMEOUT	(500 * MSEC)
 
@@ -670,14 +675,39 @@ void chipset_force_shutdown(enum chipset_shutdown_reason reason)
 
 void chipset_reset(enum chipset_reset_reason reason)
 {
-	/*
-	 * Before we can reprogram the PMIC to make the PMIC RESIN_N pin as
-	 * reset pin and zero-latency. We do cold reset instead.
-	 */
+	int rv;
+
 	CPRINTS("%s(%d)", __func__, reason);
 	report_ap_reset(reason);
 
-	request_cold_reset();
+	/* The host command is used to hard reset AP. Check b/119261783 */
+	if (reason == CHIPSET_RESET_HOST_CMD) {
+		request_cold_reset();
+		return;
+	}
+
+	/*
+	 * Warm reset sequence:
+	 * 1. Issue a low pulse to PM845_RESIN_L, which triggers PMIC
+	 *    to do a warm reset (requiring reprogramming PMIC registers
+	 *    to make PM845_RESIN_L as a warm reset trigger).
+	 * 2. PMIC then issues a low pulse to AP_RST_L to reset AP.
+	 *    EC monitors the signal to see any low pulse.
+	 *    2.1. If a low pulse found, done.
+	 *    2.2. If a low pulse not found (the above PMIC registers
+	 *         not programmed or programmed wrong), issue a request
+	 *         to initiate a cold reset power sequence.
+	 */
+
+	gpio_set_level(GPIO_PM845_RESIN_L, 0);
+	usleep(PMIC_RESIN_PULSE_LENGTH);
+	gpio_set_level(GPIO_PM845_RESIN_L, 1);
+
+	rv = power_wait_signals_timeout(IN_AP_RST_ASSERTED,
+					PMIC_POWER_AP_RESPONSE_TIMEOUT);
+	/* Exception case: PMIC not work as expected, request a cold reset */
+	if (rv != EC_SUCCESS)
+		request_cold_reset();
 }
 
 /**