[PATCH v2] arm: dts: am335x-boneblack: add gpio-line-names

From: Drew Fustini
Date: Thu May 21 2020 - 16:09:33 EST

The BeagleBone Black has P8 and P9 headers [0] which expose many of the
AM3358 ZCZ SoC balls to stacking expansion boards called "capes", or to
other external connections like jumper wires connected to a breadboard.
BeagleBone users will often refer to the "Cape Exanpsion Headers" pin
diagram [1] as it is in the "Bone101" getting started tutorial. [2]

Most of the P8 and P9 header pins can muxed to a GPIO line. The
gpio-line-names describe which P8 or P9 pin that line goes to and the
default mux for that P8 or P9 pin if it is not GPIO.

For example, gpiochip 1 line 0 is connected to P8 header pin 25 (P8_25)
however the default device tree has the corresponding BGA ball (ZCZ U7)
muxed to mmc1_dat0 as it is used for the on-board eMMC chip. For that
GPIO line to be used, one would need to modify the device tree to
disable the eMMC and change the pin mux for that ball to GPIO mode.

Some of the AM3358 ZCZ balls corresponding to GPIO lines are not routed
to a P8 or P9 header, but are instead wired to some peripheral device
like on-board eMMC, HDMI framer IC, or status LEDs. Those names are in
brackets to denote those GPIO lines can not be used.

Some GPIO lines are named "[NC]" as the corresponding balls are not
routed to anything on the PCB.

The goal for these names is to make it easier for a user viewing the
output of gpioinfo to determine which P8 or P9 pin is connected to a
GPIO line. The output of gpioinfo on a BeagleBone Black would be:

gpiochip0 - 32 lines:
line 0: "[ethernet]" unused input active-high
line 1: "[ethernet]" unused input active-high
line 2: "P9_22 [spi0_sclk]" unused input active-high
line 3: "P9_21 [spi0_d0]" unused input active-high
line 4: "P9_18 [spi0_d1]" unused input active-high
line 5: "P9_17 [spi0_cs0]" unused input active-high
line 6: "[sd card]" "cd" input active-low [used]
line 7: "P9_42A [ecappwm0]" unused input active-high
line 8: "P8_35 [hdmi]" unused input active-high
line 9: "P8_33 [hdmi]" unused input active-high
line 10: "P8_31 [hdmi]" unused input active-high
line 11: "P8_32 [hdmi]" unused input active-high
line 12: "P9_20 [i2c2_sda]" unused input active-high
line 13: "P9_19 [i2c2_scl]" unused input active-high
line 14: "P9_26 [uart1_rxd]" unused input active-high
line 15: "P9_24 [uart1_txd]" unused input active-high
line 16: "[ethernet]" unused input active-high
line 17: "[ethernet]" unused input active-high
line 18: "[usb]" unused input active-high
line 19: "[hdmi]" unused input active-high
line 20: "P9_41B" unused input active-high
line 21: "[ethernet]" unused input active-high
line 22: "P8_19 [ehrpwm2a]" unused input active-high
line 23: "P8_13 [ehrpwm2b]" unused input active-high
line 24: "[NC]" unused input active-high
line 25: "[NC]" unused input active-high
line 26: "P8_14" unused input active-high
line 27: "P8_17" unused input active-high
line 28: "[ethernet]" unused input active-high
line 29: "[ethernet]" unused input active-high
line 30: "P9_11 [uart4_rxd]" unused input active-high
line 31: "P9_13 [uart4_txd]" unused input active-high
gpiochip1 - 32 lines:
line 0: "P8_25 [emmc]" unused input active-high
line 1: "[emmc]" unused input active-high
line 2: "P8_5 [emmc]" unused input active-high
line 3: "P8_6 [emmc]" unused input active-high
line 4: "P8_23 [emmc]" unused input active-high
line 5: "P8_22 [emmc]" unused input active-high
line 6: "P8_3 [emmc]" unused input active-high
line 7: "P8_4 [emmc]" unused input active-high
line 8: "[NC]" unused input active-high
line 9: "[NC]" unused input active-high
line 10: "[NC]" unused input active-high
line 11: "[NC]" unused input active-high
line 12: "P8_12" unused input active-high
line 13: "P8_11" unused input active-high
line 14: "P8_16" unused input active-high
line 15: "P8_15" unused input active-high
line 16: "P9_15A" unused input active-high
line 17: "P9_23" unused input active-high
line 18: "P9_14 [ehrpwm1a]" unused input active-high
line 19: "P9_16 [ehrpwm1b]" unused input active-high
line 20: "[emmc]" unused input active-high
line 21: "[usr0 led]" "beaglebone:green:heartbeat" output active-high [used]
line 22: "[usr1 led]" "beaglebone:green:mmc0" output active-high [used]
line 23: "[usr2 led]" "beaglebone:green:usr2" output active-high [used]
line 24: "[usr3 led]" "beaglebone:green:usr3" output active-high [used]
line 25: "[hdmi]" "interrupt" input active-high [used]
line 26: "[usb]" unused input active-high
line 27: "[hdmi audio]" "enable" output active-high [used]
line 28: "P9_12" unused input active-high
line 29: "P8_26" unused input active-high
line 30: "P8_21 [emmc]" unused input active-high
line 31: "P8_20 [emmc]" unused input active-high
gpiochip2 - 32 lines:
line 0: "P9_15B" unused input active-high
line 1: "P8_18" unused input active-high
line 2: "P8_7" unused input active-high
line 3: "P8_8" unused input active-high
line 4: "P8_10" unused input active-high
line 5: "P8_9" unused input active-high
line 6: "P8_45 [hdmi]" unused input active-high
line 7: "P8_46 [hdmi]" unused input active-high
line 8: "P8_43 [hdmi]" unused input active-high
line 9: "P8_44 [hdmi]" unused input active-high
line 10: "P8_41 [hdmi]" unused input active-high
line 11: "P8_42 [hdmi]" unused input active-high
line 12: "P8_39 [hdmi]" unused input active-high
line 13: "P8_40 [hdmi]" unused input active-high
line 14: "P8_37 [hdmi]" unused input active-high
line 15: "P8_38 [hdmi]" unused input active-high
line 16: "P8_36 [hdmi]" unused input active-high
line 17: "P8_34 [hdmi]" unused input active-high
line 18: "[ethernet]" unused input active-high
line 19: "[ethernet]" unused input active-high
line 20: "[ethernet]" unused input active-high
line 21: "[ethernet]" unused input active-high
line 22: "P8_27 [hdmi]" unused input active-high
line 23: "P8_29 [hdmi]" unused input active-high
line 24: "P8_28 [hdmi]" unused input active-high
line 25: "P8_30 [hdmi]" unused input active-high
line 26: "[emmc]" unused input active-high
line 27: "[emmc]" unused input active-high
line 28: "[emmc]" unused input active-high
line 29: "[emmc]" unused input active-high
line 30: "[emmc]" unused input active-high
line 31: "[emmc]" unused input active-high
gpiochip3 - 32 lines:
line 0: "[ethernet]" unused input active-high
line 1: "[ethernet]" unused input active-high
line 2: "[ethernet]" unused input active-high
line 3: "[ethernet]" unused input active-high
line 4: "[ethernet]" unused input active-high
line 5: "[i2c0]" unused input active-high
line 6: "[i2c0]" unused input active-high
line 7: "[emu]" unused input active-high
line 8: "[emu]" unused input active-high
line 9: "[ethernet]" unused input active-high
line 10: "[ethernet]" unused input active-high
line 11: "[NC]" unused input active-high
line 12: "[NC]" unused input active-high
line 13: "[usb]" unused input active-high
line 14: "P9_31 [spi1_sclk]" unused input active-high
line 15: "P9_29 [spi1_d0]" unused input active-high
line 16: "P9_30 [spi1_d1]" unused input active-high
line 17: "P9_28 [spi1_cs0]" unused input active-high
line 18: "P9_42B [ecappwm0]" unused input active-high
line 19: "P9_27" unused input active-high
line 20: "P9_41A" unused input active-high
line 21: "P9_25" unused input active-high
line 22: "[NC]" unused input active-high
line 23: "[NC]" unused input active-high
line 24: "[NC]" unused input active-high
line 25: "[NC]" unused input active-high
line 26: "[NC]" unused input active-high
line 27: "[NC]" unused input active-high
line 28: "[NC]" unused input active-high
line 29: "[NC]" unused input active-high
line 30: "[NC]" unused input active-high
line 31: "[NC]" unused input active-high

[0] https://git.io/JfgOd
[1] https://beagleboard.org/capes
[1] https://beagleboard.org/Support/bone101
[2] https://beagleboard.org/static/images/cape-headers.png

Reviewed-by: Jason Kridner <jason@xxxxxxxxxxxxxxx>
Reviewed-by: Robert Nelson <robertcnelson@xxxxxxxxx>
Signed-off-by: Drew Fustini <drew@xxxxxxxxxxxxxxx>
---
V2 change:
- include output of gpioinfo to illustrate how the gpio-line-names
will appear. My apologies for forgetting to include in V1.

V1 note:
I had posted a patch with these line names for am335x-bone-common.dtsi
but Grygorii Strashko pointed out that the names are not applicable to
all BeagleBone models. Thus I have created this patch to add these
names just for the BeagleBone Black.

arch/arm/boot/dts/am335x-boneblack.dts | 144 +++++++++++++++++++++++++
1 file changed, 144 insertions(+)

diff --git a/arch/arm/boot/dts/am335x-boneblack.dts b/arch/arm/boot/dts/am335x-boneblack.dts
index d3928662aed4..5f31e832eb82 100644
--- a/arch/arm/boot/dts/am335x-boneblack.dts
+++ b/arch/arm/boot/dts/am335x-boneblack.dts
@@ -23,3 +23,147 @@ oppnitro-1000000000 {
opp-supported-hw = <0x06 0x0100>;
};
};
+
+&gpio0 {
+ gpio-line-names =
+ "[ethernet]",
+ "[ethernet]",
+ "P9_22 [spi0_sclk]",
+ "P9_21 [spi0_d0]",
+ "P9_18 [spi0_d1]",
+ "P9_17 [spi0_cs0]",
+ "[sd card]",
+ "P9_42A [ecappwm0]",
+ "P8_35 [hdmi]",
+ "P8_33 [hdmi]",
+ "P8_31 [hdmi]",
+ "P8_32 [hdmi]",
+ "P9_20 [i2c2_sda]",
+ "P9_19 [i2c2_scl]",
+ "P9_26 [uart1_rxd]",
+ "P9_24 [uart1_txd]",
+ "[ethernet]",
+ "[ethernet]",
+ "[usb]",
+ "[hdmi]",
+ "P9_41B",
+ "[ethernet]",
+ "P8_19 [ehrpwm2a]",
+ "P8_13 [ehrpwm2b]",
+ "[NC]",
+ "[NC]",
+ "P8_14",
+ "P8_17",
+ "[ethernet]",
+ "[ethernet]",
+ "P9_11 [uart4_rxd]",
+ "P9_13 [uart4_txd]";
+};
+
+&gpio1 {
+ gpio-line-names =
+ "P8_25 [emmc]",
+ "[emmc]",
+ "P8_5 [emmc]",
+ "P8_6 [emmc]",
+ "P8_23 [emmc]",
+ "P8_22 [emmc]",
+ "P8_3 [emmc]",
+ "P8_4 [emmc]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "P8_12",
+ "P8_11",
+ "P8_16",
+ "P8_15",
+ "P9_15A",
+ "P9_23",
+ "P9_14 [ehrpwm1a]",
+ "P9_16 [ehrpwm1b]",
+ "[emmc]",
+ "[usr0 led]",
+ "[usr1 led]",
+ "[usr2 led]",
+ "[usr3 led]",
+ "[hdmi]",
+ "[usb]",
+ "[hdmi audio]",
+ "P9_12",
+ "P8_26",
+ "P8_21 [emmc]",
+ "P8_20 [emmc]";
+};
+
+&gpio2 {
+ gpio-line-names =
+ "P9_15B",
+ "P8_18",
+ "P8_7",
+ "P8_8",
+ "P8_10",
+ "P8_9",
+ "P8_45 [hdmi]",
+ "P8_46 [hdmi]",
+ "P8_43 [hdmi]",
+ "P8_44 [hdmi]",
+ "P8_41 [hdmi]",
+ "P8_42 [hdmi]",
+ "P8_39 [hdmi]",
+ "P8_40 [hdmi]",
+ "P8_37 [hdmi]",
+ "P8_38 [hdmi]",
+ "P8_36 [hdmi]",
+ "P8_34 [hdmi]",
+ "[ethernet]",
+ "[ethernet]",
+ "[ethernet]",
+ "[ethernet]",
+ "P8_27 [hdmi]",
+ "P8_29 [hdmi]",
+ "P8_28 [hdmi]",
+ "P8_30 [hdmi]",
+ "[emmc]",
+ "[emmc]",
+ "[emmc]",
+ "[emmc]",
+ "[emmc]",
+ "[emmc]";
+};
+
+&gpio3 {
+ gpio-line-names =
+ "[ethernet]",
+ "[ethernet]",
+ "[ethernet]",
+ "[ethernet]",
+ "[ethernet]",
+ "[i2c0]",
+ "[i2c0]",
+ "[emu]",
+ "[emu]",
+ "[ethernet]",
+ "[ethernet]",
+ "[NC]",
+ "[NC]",
+ "[usb]",
+ "P9_31 [spi1_sclk]",
+ "P9_29 [spi1_d0]",
+ "P9_30 [spi1_d1]",
+ "P9_28 [spi1_cs0]",
+ "P9_42B [ecappwm0]",
+ "P9_27",
+ "P9_41A",
+ "P9_25",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]",
+ "[NC]";
+};
--
2.25.1