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| author | Fabio Baltieri <fabiobaltieri@google.com> | 2022-08-09 05:55:50 +0100 |
|---|---|---|
| committer | Chromeos LUCI <chromeos-scoped@luci-project-accounts.iam.gserviceaccount.com> | 2022-08-10 07:56:31 +0000 |
| commit | 1b6e7b4659e0b4e03f679ddff1e445db271f7433 (patch) | |
| tree | d2d08f9b11044caa9d82f3d7298bee3fba0c2ec2 /docs/zephyr | |
| parent | 6784ec01a55a487470fdffc6bee4469eb2885363 (diff) | |
| download | chrome-ec-1b6e7b4659e0b4e03f679ddff1e445db271f7433.tar.gz | |
zephyr: doc: add a note about alternate function GPIOs
On NPCX platforms some pins default to a specific (non GPIO) function
after reset, but are switched to GPIO in the initialization code. This
may be confusing if one is only referencing the manual default pin
multiplexing configuration.
Adding a note about that in the GPIO doc page to reference this
behavior.
BRANCH=none
BUG=b:241734677
TEST=check the page on gitiles
Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>
Change-Id: I3f6fa9f93c339771e15ac5b62c53442b28d1d2ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3817775
Reviewed-by: Madhu P <mparuchuri@google.com>
Reviewed-by: Al Semjonovs <asemjonovs@google.com>
Diffstat (limited to 'docs/zephyr')
| -rw-r--r-- | docs/zephyr/zephyr_gpio.md | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/docs/zephyr/zephyr_gpio.md b/docs/zephyr/zephyr_gpio.md index 8dbf1ea5c8..5204e6107f 100644 --- a/docs/zephyr/zephyr_gpio.md +++ b/docs/zephyr/zephyr_gpio.md @@ -70,6 +70,15 @@ included from the main board DTS file. For platform specific features, other flags may be available in the Zephyr [dt-bindings/gpio/gpio.h] file, such as `GPIO_VOLTAGE_1P8`. +### Alternate functions + +All pins are configured as GPIO by default, so normally pinctrl configuration +for GPIO pins is not required. Note that on NPCX ECs some pins default to a +non-GPIO function after reset. These are explicitly set to GPIO during +initialization, based on the `def-io-conf-list` node in [npcx9.dtsi], so they +do not need to be set to GPIO usage, but they need an explicit `pinctrl-x` +entry to be set back to the specific function. + ### Legacy enum-name usage Only GPIOs that require referencing from legacy common code should have @@ -456,4 +465,5 @@ project. [gpio.dts]: ../../zephyr/projects/volteer/volteer/gpio.dts [interrupts.dts]: ../../zephyr/projects/volteer/volteer/interrupts.dts [BUILD.py]: ../../zephyr/projects/volteer/volteer/BUILD.py -[*node label*]: https://docs.zephyrproject.org/latest/build/dts/intro.html#dt-node-labels
\ No newline at end of file +[*node label*]: https://docs.zephyrproject.org/latest/build/dts/intro.html#dt-node-labels +[npcx9.dtsi]: https://github.com/zephyrproject-rtos/zephyr/blob/main/dts/arm/nuvoton/npcx9.dtsi |