[PATCH 2/4] arm64: dts: mediatek: mt7986: add gpio-hog for boot mode switch on BPI-R3

[Leith Bade]

To avoid future pin conflicts with the boot mode dip switch (SW1), add
a gpio-hog to document the two GPIOs it is connected to. If another device
attempts to then claim the pins a log message will get printed.

The BPI-R3 has a four position DIP switch (labelled SW1), that is used to
configure the boot mode. The first two positions (labelled A & B)
configure two bootstrap pins on the MT7986 that select which flash chip
the boot ROM will load the second stage bootloader from. The third
position toggles chip select lines to select between the NOR or NAND chip
on the SPI0 bus. The fourth position toggles chip select lines to select
between the eMMC chip or SD card on the MMC0 bus.

Only the first two positions are connected to GPIO pins on the MT7986. In
the public schematic for the BPI-R3 (titled "BPI-R3-MT7986A",
revision "V1.1", sheet 4), these are the MT7986 (U1E) pins GPIO_0 (GPIO5)
and GPIO_1 (GPIO6). This gpio-hog configures the two boot mode pins as
inputs.

Signed-off-by: Leith Bade <leith at bade.nz>
---
 arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
index 951612ea1e66..2cccbec39d34 100644
--- a/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
+++ b/arch/arm64/boot/dts/mediatek/mt7986a-bananapi-bpi-r3.dts
@@ -235,6 +235,13 @@ &pcie_phy {
 };
 
 &pio {
+	boot_mode_hog: boot-mode-hog {
+		gpio-hog;
+		gpios = <5 GPIO_ACTIVE_HIGH>,
+			<6 GPIO_ACTIVE_HIGH>;
+		input;
+	};
+
 	i2c_pins: i2c-pins {
 		mux {
 			function = "i2c";
-- 
2.25.1