Re: [PATCH] Eliminate Odroid HC4 power glitches during boot.
From: Ricardo Pardini <hidden>
Date: 2026-01-20 01:32:08
Also in:
linux-amlogic, linux-devicetree, lkml
On 17/01/2026 05:02, Eric Neulight via B4 Relay wrote:
quoted hunk ↗ jump to hunk
Fix issue with Odroid HC4 (and all meson-sm1-odroid) DTS that causes regulator power to momentarily glitch OFF-ON during boot. Add regulator-boot-on to all regulator-fixed and regulator-gpio entries that (1) define a gpio AND (2) define regulator-always-on. U-boot powers on devices necessary for boot then hands off the DTB to the kernel. During probe, linux drivers/regulator/fixed.c and gpio-regulator.c both first set the regulator control gpio (that U-boot already turned ON) to default OFF before then setting it to the defined (ON) state. This glitches the power to the affected devices, unless regulator-boot-on is specified with it. In fact, U-boot has the same behavior. So, during reboot, a power glitch can actually happen twice: once when U-boot reads the DTB and probes the gpio and again when the kernel reads the DTB and probes the gpio. Problem this fixes: On the Odroid HC4, power to the SATA ports glitches during boot and causes some HDDs to do emergency head retract, which should be avoided. On the HC4, power glitches to the SD card, USB, SATA, and HDMI interfaces during boot. These are all boot devices. A power glitch can potentially cause a problem for any sensitive devices during boot. NOTE: This is not limited to just the HC4, likely an issue with ALL DTS with regulator-fixed or regulator-gpio entries that (1) define a gpio AND (2) define regulator-always-on. All such entries should also include regulator-boot-on in order to avoid potential power glitches. At worst, adding regulator-boot-on in such cases is harmless because of regulator-always-on, and, at best, it eliminates detrimental power glitches during boot. So, this is best-practice. Fixes: 164147f094ec5d0fc2c2098a888f4b50cf3096a7 ("arm64: dts: meson-sm1-odroid-hc4: add regulators controlled by GPIOH_8") Fixes: 45d736ab17b44257e15e75e0dba364139fdb0983 ("arm64: dts: meson-sm1-odroid: add 5v regulator gpio") Fixes: 1f80a5cf74a60997b92d2cde772edec093bec4d9 ("arm64: dts: meson-sm1-odroid: add missing enable gpio and supply for tf_io regulator") Fixes: 88d537bc92ca035e2a9920b0abc750dd62146520 ("arm64: dts: meson: convert meson-sm1-odroid-c4 to dtsi") Signed-off-by: Eric Neulight <redacted> --- arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts | 2 ++ arch/arm64/boot/dts/amlogic/meson-sm1-odroid.dtsi | 3 +++ 2 files changed, 5 insertions(+)diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts b/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts index 0170139b8d32f4274ad991b0f3d9a0f6c67969ce..3ece30a0a1fff736c544cf89ed0a8cca0890f128 100644 --- a/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts +++ b/arch/arm64/boot/dts/amlogic/meson-sm1-odroid-hc4.dts@@ -52,6 +52,7 @@ p12v_0: regulator-p12v-0 { gpio = <&gpio GPIOH_8 GPIO_OPEN_DRAIN>; enable-active-high; + regulator-boot-on; regulator-always-on; };@@ -65,6 +66,7 @@ p12v_1: regulator-p12v-1 { gpio = <&gpio GPIOH_8 GPIO_OPEN_DRAIN>; enable-active-high; + regulator-boot-on; regulator-always-on; };diff --git a/arch/arm64/boot/dts/amlogic/meson-sm1-odroid.dtsi b/arch/arm64/boot/dts/amlogic/meson-sm1-odroid.dtsi index c4524eb4f0996dfbccec16ca5b936a5c3b2663a5..0bce4e8d965f2c83e6ba677fef2ede2726de6ed1 100644 --- a/arch/arm64/boot/dts/amlogic/meson-sm1-odroid.dtsi +++ b/arch/arm64/boot/dts/amlogic/meson-sm1-odroid.dtsi@@ -37,6 +37,7 @@ tflash_vdd: regulator-tflash-vdd { gpio = <&gpio_ao GPIOAO_3 GPIO_OPEN_DRAIN>; enable-active-high; + regulator-boot-on; regulator-always-on; };@@ -50,6 +51,7 @@ tf_io: gpio-regulator-tf-io { enable-gpios = <&gpio_ao GPIOE_2 GPIO_OPEN_DRAIN>; enable-active-high; + regulator-boot-on; regulator-always-on; gpios = <&gpio_ao GPIOAO_6 GPIO_OPEN_SOURCE>;@@ -81,6 +83,7 @@ vcc_5v: regulator-vcc-5v { regulator-name = "5V"; regulator-min-microvolt = <5000000>; regulator-max-microvolt = <5000000>; + regulator-boot-on; regulator-always-on; vin-supply = <&main_12v>; gpio = <&gpio GPIOH_8 GPIO_OPEN_DRAIN>;--- base-commit: b71e635feefc852405b14620a7fc58c4c80c0f73 change-id: 20260116-odroid-hc4-dts-54f4254d8554 Best regards,
Tested with 6.19-rc5 base on an Odroid-HC4 running with a single 2.5" HDD. This patch does not solve (as I hoped) unrelated/long standing issues like the "famous" disk noise at/~around PCIe/AHCI probe time nor the fact the 5V rail can't properly power two 5V disks when at least one of them is spinning rust -- but also doesn't cause any new problems that I can detect (SMART etc). I hope someone with 12V disks could take a this for a spin and report further; I really can't take mine out of "production" anytime soon. Tested-by: Ricardo Pardini <redacted> # on Odroid-HC4 5V HDD Thanks, Ricardo