Enable the vcc3v0_sd regulator on boot so that the device can boot from the
uSD card (when using certain uSD cards).

Upstream-Status: Submitted [http://lists.infradead.org/pipermail/linux-arm-kernel/2021-October/688254.html]

Signed-off-by: Trevor Woerner <twoerner@...>
---
....dtsi-enable-sdmmc-regulator-on-boot.patch | 47 +++++++++++++++++++
recipes-kernel/linux/linux-yocto%.bbappend | 1 +
2 files changed, 48 insertions(+)
create mode 100644 recipes-kernel/linux/files/0001-rk3399-nanopi4.dtsi-enable-sdmmc-regulator-on-boot.patch

diff --git a/recipes-kernel/linux/files/0001-rk3399-nanopi4.dtsi-enable-sdmmc-regulator-on-boot.patch b/recipes-kernel/linux/files/0001-rk3399-nanopi4.dtsi-enable-sdmmc-regulator-on-boot.patch
new file mode 100644
index 0000000..c871c5a
--- /dev/null
+++ b/recipes-kernel/linux/files/0001-rk3399-nanopi4.dtsi-enable-sdmmc-regulator-on-boot.patch
@@ -0,0 +1,47 @@
+From 33e3f2f8b22c226977b6461581ae113c3f77f5fd Mon Sep 17 00:00:00 2001
+From: Trevor Woerner <twoerner@...>
+Date: Wed, 6 Oct 2021 11:41:23 -0400
+Subject: [PATCH] rk3399-nanopi4.dtsi: enable sdmmc regulator on boot
+
+When trying to boot a nanopi-m4 board with an SDHC-class uSD card, the boot
+comes to a full stop shortly after initializing the mmc subsystem. The boot
+can be cajoled into continuing if, after waiting a minute or so, the uSD
+card is ejected and re-inserted. Waiting a minute or so before ejecting and
+re-inserting the uSD card is crucial since the boot will not continue if
+the card is ejected/re-inserted too soon after the boot has stopped.
+
+The nanopi-m4 has a uSD card and an optional eMMC module, either of which
+can be used for booting. In my case I don't have the optional eMMC module,
+therefore I'm booting from the uSD card. When booting from the uSD card,
+its regulator needs to be enabled at boot.
+
+Curiously, this should have been an issue from day one, but it only started
+to become a problem after commit 98e48cd9283d ("regulator: core: resolve
+supply for boot-on/always-on regulators") was merged. Additionally, by
+coincidence, I happened to be using an SDHC-class card in my device, and
+saw the failure. However, if I use an SDXC-class uSD card the problem does
+not occur.
+
+Much thanks to Mark Brown and Javier Martinez Canillas for their assistance
+on irc!
+
+Signed-off-by: Trevor Woerner <twoerner@...>
+---
+ arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi | 1 +
+ 1 file changed, 1 insertion(+)
+
+diff --git a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
+index 8c0ff6c96e03..5cf02e2ef9b3 100644
+--- a/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
++++ b/arch/arm64/boot/dts/rockchip/rk3399-nanopi4.dtsi
+@@ -71,6 +71,7 @@ vcc3v0_sd: vcc3v0-sd {
+ pinctrl-names = "default";
+ pinctrl-0 = <&sdmmc0_pwr_h>;
+ regulator-always-on;
++ regulator-boot-on;
+ regulator-min-microvolt = <3000000>;
+ regulator-max-microvolt = <3000000>;
+ regulator-name = "vcc3v0_sd";
+--
+2.30.0.rc0
+
diff --git a/recipes-kernel/linux/linux-yocto%.bbappend b/recipes-kernel/linux/linux-yocto%.bbappend
index 470dc09..61d5116 100644
--- a/recipes-kernel/linux/linux-yocto%.bbappend
+++ b/recipes-kernel/linux/linux-yocto%.bbappend
@@ -12,3 +12,4 @@ COMPATIBLE_MACHINE:rock64 = "rock64"
COMPATIBLE_MACHINE:rock-pi-e = "rock-pi-e"

FILESEXTRAPATHS:prepend := "${THISDIR}/files:"
+SRC_URI:append:nanopi-m4 = " file://0001-rk3399-nanopi4.dtsi-enable-sdmmc-regulator-on-boot.patch"
--
2.30.0.rc0