pwrseq: gpio: Use output state for GPIO get on outputs

When retrieving the state of an output GPIO, do not read
the physical level on the pin, but instead read the configured
state (by reading the GPIO configuration).

Open drain outputs sometimes use low voltages, and so
reading the physical level on the pin may indicate a
0 for an output that has been set to 1.

The stored configuration of the GPIO does not include
the GPIO_ACTIVE_LOW flag, so this is explicitly checked, and
the state inverted if necessary.

BUG=none
TEST=zmake build nivviks; flash & run
BRANCH=none

Signed-off-by: Andrew McRae <amcrae@google.com>
Change-Id: Idb2cb1c6b1b0902189e1fd1471cf9ca30c2711dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3769706
Reviewed-by: Peter Marheine <pmarheine@chromium.org>

2 files changed, 25 insertions, 0 deletions

diff --git a/zephyr/subsys/ap_pwrseq/Kconfig b/zephyr/subsys/ap_pwrseq/Kconfig
index 6f39906bf2..1845baa2bd 100644
--- a/zephyr/subsys/ap_pwrseq/Kconfig
+++ b/zephyr/subsys/ap_pwrseq/Kconfig
@@ -5,12 +5,15 @@
 menuconfig AP_PWRSEQ
 	bool "AP Power sequencing support"
 	select HAS_TASK_POWERBTN
+	select GPIO_GET_CONFIG
 	help
 	  Enables AP power sequencing support with
 	  embedded controller. This includes normal shutdown, critical
 	  shutdown and reset handling.
 	  Enabling this automatically enables HAS_TASK_POWERBTN since this task
 	  is required to handle power button pressed/released by user.
+	  Enabling this also enables retrieving the GPIO config feature
+	  so that the value of output GPIOs can be determined.
 
 if AP_PWRSEQ
 
diff --git a/zephyr/subsys/ap_pwrseq/signal_gpio.c b/zephyr/subsys/ap_pwrseq/signal_gpio.c
index f4b74fd3be..4d21657624 100644
--- a/zephyr/subsys/ap_pwrseq/signal_gpio.c
+++ b/zephyr/subsys/ap_pwrseq/signal_gpio.c
@@ -100,6 +100,28 @@ int power_signal_gpio_get(enum pwr_sig_gpio index)
 	if (index < 0 || index >= ARRAY_SIZE(gpio_config)) {
 		return -EINVAL;
 	}
+	/*
+	 * Getting the current value of an output is
+	 * done by retrieving the config and checking what the
+	 * output state has been set to, not by reading the
+	 * physical level of the pin (open drain outputs
+	 * may have a low voltage).
+	 */
+	if (gpio_config[index].output) {
+		int rv;
+		gpio_flags_t flags;
+
+		rv = gpio_pin_get_config_dt(&spec[index], &flags);
+		if (rv != 0) {
+			return rv;
+		}
+		rv = (flags & GPIO_OUTPUT_INIT_HIGH) ? 1 : 0;
+		/* If active low signal, invert it */
+		if (spec[index].dt_flags & GPIO_ACTIVE_LOW) {
+			rv = !rv;
+		}
+		return rv;
+	}
 	return gpio_pin_get_dt(&spec[index]);
 }