Re: [PATCH 10/13] arm64: dts: ti: k3-j7200: Enable GPIO nodes at the board level

From: Andrew Davis
Date: Mon Aug 07 2023 - 12:16:45 EST

On 8/7/23 10:42 AM, Nishanth Menon wrote:
On 10:28-20230807, Andrew Davis wrote:
On 8/7/23 12:38 AM, Dhruva Gole wrote:

On 03/08/23 02:23, Andrew Davis wrote:
GPIO nodes defined in the top-level J7200 SoC dtsi files are incomplete
and may not be functional unless they are extended with pinmux and
device information.

Disable the GPIO nodes in the dtsi files and only enable the ones that
are actually pinned out on a given board.

Signed-off-by: Andrew Davis <afd@xxxxxx>
  .../boot/dts/ti/k3-j7200-common-proc-board.dts | 18 ++++--------------
  arch/arm64/boot/dts/ti/k3-j7200-main.dtsi      |  4 ++++
  .../arm64/boot/dts/ti/k3-j7200-mcu-wakeup.dtsi |  2 ++
  3 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/arch/arm64/boot/dts/ti/k3-j7200-common-proc-board.dts b/arch/arm64/boot/dts/ti/k3-j7200-common-proc-board.dts
index dee9056f56051..4a5c4f36baeec 100644
--- a/arch/arm64/boot/dts/ti/k3-j7200-common-proc-board.dts
+++ b/arch/arm64/boot/dts/ti/k3-j7200-common-proc-board.dts
@@ -240,27 +240,17 @@ &main_uart3 {
      pinctrl-0 = <&main_uart3_pins_default>;
-&main_gpio2 {
-    status = "disabled";
-&main_gpio4 {
-    status = "disabled";
-&main_gpio6 {
-    status = "disabled";
+&main_gpio0 {
+    status = "okay";
+    /* default pins */

Small question, where is the pmx for main_gpio0? What does "default pins"
refer to here? Where are they pinmuxed?

Good question, where is the pmx for main_gpio0? I don't know, it was
never defined before either, we only are noticing this now as we are
disabling by default instead of leaving an unfinished node enabled
by default. (another benefit of this disabled by default scheme).

What is really happening is GPIO nodes we tend to pinmux differently
than normal device nodes. Their pinmux selections tends to be spread
out in all the nodes that make use of these GPIO pins, not all together
here in this node.

For instance in this device we use one of the main_gpio0 pins as a
GPIO toggled regulator, and we define the pinmux for it in that node
(see vdd-sd-dv-default-pins).

We can either define the rest of the pins not used elsewhere
here, or we can consider GPIO an exception to the rule, I'd say
the latter is fine for now.

GPIO pinmux are typically defined where they need - the only place where
they are explicitly called out in gpio is when they are meant to be used by
libgpio - typically in the case of dev boards.

Just drop the comments of /* default pins */ - that is just mis-leading.

True, will drop the comment for v2.