diff options
| author | Wai-Hong Tam <waihong@google.com> | 2022-03-15 16:56:44 -0700 |
|---|---|---|
| committer | Commit Bot <commit-bot@chromium.org> | 2022-03-16 18:07:09 +0000 |
| commit | 6e5d4978a9f31b62d5a8d2356b7e06ecea0bdb56 (patch) | |
| tree | c4ab8dd9c9735b061b54eea281e80c325c17e008 | |
| parent | a17c70ef114aa087ac36860ec4cd40fd62d536db (diff) | |
| download | chrome-ec-6e5d4978a9f31b62d5a8d2356b7e06ecea0bdb56.tar.gz | |
zephyr: gpio: Do not change the output state for open-drain outputs
In the GPIO init, for each OUTPUT GPIO, it changes its output state
according to its current state. It works for a push-pull OUTPUT.
But for an open drain output, its current value doesn't imply the
previous output state. The current low state is either
1) the EC previously drove the pin low;
2) the EC previously high-Z'ed the pin.
These 2 cases can't be differentiated, so skip overriding the output
state.
BRANCH=None
BUG=b:224616711
TEST=Verified the EC RW can boot the AP into the logic prompt.
Change-Id: Ifdd1c6bac74b80edd95e9075744e1e583d553a0e
Signed-off-by: Wai-Hong Tam <waihong@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3530149
Reviewed-by: Keith Short <keithshort@chromium.org>
| -rw-r--r-- | zephyr/shim/src/gpio.c | 18 |
1 files changed, 16 insertions, 2 deletions
diff --git a/zephyr/shim/src/gpio.c b/zephyr/shim/src/gpio.c index 59d59d78f7..6eb9a142ad 100644 --- a/zephyr/shim/src/gpio.c +++ b/zephyr/shim/src/gpio.c @@ -286,8 +286,22 @@ static int init_gpios(const struct device *unused) flags &= ~(GPIO_OUTPUT_INIT_LOW | GPIO_OUTPUT_INIT_HIGH); - flags |= current ? GPIO_OUTPUT_INIT_HIGH - : GPIO_OUTPUT_INIT_LOW; + + /* + * For an open drain output, its current value + * doesn't imply the previous output state. + * + * The current low state is either + * 1) the EC previously drove the pin low; + * 2) the EC previously high-Z'ed the pin. + * + * These 2 cases can't be differentiated, so + * skip overriding the output state. + */ + if ((flags & GPIO_OPEN_DRAIN) != GPIO_OPEN_DRAIN) { + flags |= current ? GPIO_OUTPUT_INIT_HIGH + : GPIO_OUTPUT_INIT_LOW; + } } rv = gpio_pin_configure_dt(&configs[i].spec, flags); |