[PATCH 0/2] arm64: dts: imx91/imx93: add rtc1 alias for external PCF2131 RTC

[PATCH 0/2] arm64: dts: imx91/imx93: add rtc1 alias for external PCF2131 RTC

[Joy Zou]

Only rtc0 was aliased to the internal bbnsm_rtc, while the external
PCF2131 RTC had no fixed index. When both RTC drivers are built as
modules, the pcf2131 may probe first and take rtc0, pushing bbnsm_rtc
to rtc1. Since suspend/resume wakeup relies on the internal bbnsm RTC
being rtc0, this broke wakeup.

Add an rtc1 alias for the PCF2131 on the i.MX91 and i.MX93 EVK/QSB
boards, so the external RTC keeps a fixed index while bbnsm_rtc always
stays rtc0.

Signed-off-by: Joy Zou <joy.zou@oss.nxp.com>
---
Joy Zou (2):
      arm64: dts: imx91-evk/qsb: add rtc1 alias for external PCF2131 RTC
      arm64: dts: imx93-evk/qsb: add rtc1 alias for external PCF2131 RTC

 arch/arm64/boot/dts/freescale/imx91-11x11-evk.dts         | 1 +
 arch/arm64/boot/dts/freescale/imx91-9x9-qsb.dts           | 1 +
 arch/arm64/boot/dts/freescale/imx93-11x11-evk-common.dtsi | 1 +
 arch/arm64/boot/dts/freescale/imx93-9x9-qsb.dts           | 3 ++-
 4 files changed, 5 insertions(+), 1 deletion(-)
---
base-commit: c68a982815dcce5464e3bf2a31ac94f5146c04ca
change-id: 20260914-b4_imx91_93_rtc-07d17cf027ab

Best regards,
--  
Joy Zou <joy.zou@oss.nxp.com>

[PATCH 1/2] arm64: dts: imx91-evk/qsb: add rtc1 alias for external PCF2131 RTC

[Joy Zou]

Only rtc0 was aliased to bbnsm_rtc, while the external pcf2131 had
no fixed index. When both drivers are modules, the pcf2131 may register
first and take rtc0, pushing bbnsm_rtc to rtc1. Since suspend/resume
wakeup relies on the internal bbnsm RTC at rtc0, this broke wakeup.

Add rtc1 alias for the pcf2131 on imx91-11x11-evk and imx91-9x9-qsb,
so it keeps a fixed index while bbnsm_rtc stays rtc0.

Signed-off-by: Joy Zou <joy.zou@oss.nxp.com>
---
 arch/arm64/boot/dts/freescale/imx91-11x11-evk.dts | 1 +
 arch/arm64/boot/dts/freescale/imx91-9x9-qsb.dts   | 1 +
 2 files changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/freescale/imx91-11x11-evk.dts b/arch/arm64/boot/dts/freescale/imx91-11x11-evk.dts
index 5716febb5a50..ea7852da43b9 100644
--- a/arch/arm64/boot/dts/freescale/imx91-11x11-evk.dts
+++ b/arch/arm64/boot/dts/freescale/imx91-11x11-evk.dts
@@ -25,6 +25,7 @@ aliases {
 		mmc1 = &usdhc2;
 		mmc2 = &usdhc3;
 		rtc0 = &bbnsm_rtc;
+		rtc1 = &pcf2131;
 		serial0 = &lpuart1;
 		serial1 = &lpuart2;
 		serial2 = &lpuart3;
diff --git a/arch/arm64/boot/dts/freescale/imx91-9x9-qsb.dts b/arch/arm64/boot/dts/freescale/imx91-9x9-qsb.dts
index f1ed7983226b..b7f0e39b867a 100644
--- a/arch/arm64/boot/dts/freescale/imx91-9x9-qsb.dts
+++ b/arch/arm64/boot/dts/freescale/imx91-9x9-qsb.dts
@@ -23,6 +23,7 @@ aliases {
 		mmc0 = &usdhc1;
 		mmc1 = &usdhc2;
 		rtc0 = &bbnsm_rtc;
+		rtc1 = &pcf2131;
 		serial0 = &lpuart1;
 	};
 

-- 
2.34.1

[PATCH 2/2] arm64: dts: imx93-evk/qsb: add rtc1 alias for external PCF2131 RTC

[Joy Zou]

Only rtc0 was aliased to bbnsm_rtc, while the external pcf2131 had
no fixed index. When both drivers are modules, the pcf2131 may register
first and take rtc0, pushing bbnsm_rtc to rtc1. Since suspend/resume
wakeup relies on the internal bbnsm RTC at rtc0, this broke wakeup.

Add rtc1 alias for the pcf2131 on imx93-11x11-evk and imx93-9x9-qsb,
so it keeps a fixed index while bbnsm_rtc stays rtc0.

Signed-off-by: Joy Zou <joy.zou@oss.nxp.com>
---
 arch/arm64/boot/dts/freescale/imx93-11x11-evk-common.dtsi | 1 +
 arch/arm64/boot/dts/freescale/imx93-9x9-qsb.dts           | 3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/freescale/imx93-11x11-evk-common.dtsi b/arch/arm64/boot/dts/freescale/imx93-11x11-evk-common.dtsi
index f48e7947cf64..2f3f9ebd3345 100644
--- a/arch/arm64/boot/dts/freescale/imx93-11x11-evk-common.dtsi
+++ b/arch/arm64/boot/dts/freescale/imx93-11x11-evk-common.dtsi
@@ -18,6 +18,7 @@ aliases {
 		mmc0 = &usdhc1;
 		mmc1 = &usdhc2;
 		rtc0 = &bbnsm_rtc;
+		rtc1 = &pcf2131;
 		serial0 = &lpuart1;
 		serial1 = &lpuart2;
 		serial2 = &lpuart3;
diff --git a/arch/arm64/boot/dts/freescale/imx93-9x9-qsb.dts b/arch/arm64/boot/dts/freescale/imx93-9x9-qsb.dts
index 01c11c517986..4e31a78963fe 100644
--- a/arch/arm64/boot/dts/freescale/imx93-9x9-qsb.dts
+++ b/arch/arm64/boot/dts/freescale/imx93-9x9-qsb.dts
@@ -28,6 +28,7 @@ aliases {
 		mmc0 = &usdhc1;
 		mmc1 = &usdhc2;
 		rtc0 = &bbnsm_rtc;
+		rtc1 = &pcf2131;
 		serial0 = &lpuart1;
 		serial1 = &lpuart2;
 		serial2 = &lpuart3;
@@ -306,7 +307,7 @@ typec1_dr_sw: endpoint {
 		};
 	};
 
-	rtc@53 {
+	pcf2131: rtc@53 {
 		compatible = "nxp,pcf2131";
 		reg = <0x53>;
 		interrupt-parent = <&pcal6524>;

-- 
2.34.1

Re: [PATCH 2/2] arm64: dts: imx93-evk/qsb: add rtc1 alias for external PCF2131 RTC

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but several other NXP boards with multiple RTCs lack explicit RTC aliases, leading to the exact same unpredictable /dev/rtcN numbering that this patch fixes.
--

commit 3914a89ee5c45116b8135c7ac05a01b772cb8462
Author: Joy Zou <joy.zou@oss.nxp.com>

arm64: dts: imx93-evk/qsb: add rtc1 alias for external PCF2131 RTC

This commit fixes unpredictable /dev/rtcN numbering for imx93 boards by adding
an explicit rtc1 alias.

> Only rtc0 was aliased to bbnsm_rtc, while the external pcf2131 had
> no fixed index. When both drivers are modules, the pcf2131 may register
> first and take rtc0, pushing bbnsm_rtc to rtc1. Since suspend/resume
> wakeup relies on the internal bbnsm RTC at rtc0, this broke wakeup.
> 
> Add rtc1 alias for the pcf2131 on imx93-11x11-evk and imx93-9x9-qsb,
> so it keeps a fixed index while bbnsm_rtc stays rtc0.

[Severity: High]
This isn't a bug introduced by this patch, but several other NXP boards with
multiple RTCs lack explicit RTC aliases, leading to the exact same
unpredictable /dev/rtcN numbering that this patch fixes.

For example, in arch/arm64/boot/dts/freescale/imx8mn-dimonoff-gateway-evk.dts:

	rtc@53 {
		compatible = "nxp,pcf2131";

This board defines multiple RTCs (pcf2129 and pcf2131) without aliases,
leaving them susceptible to the same index race condition.

In arch/arm64/boot/dts/freescale/imx8mp-navqp.dts:

	rtc@53 {
		compatible = "nxp,pcf2131";

This board defines an external RTC alongside the SoC's internal snvs_rtc
without any aliases, causing unpredictable index assignment.

In arch/arm64/boot/dts/freescale/fsl-ls1088a-rdb.dts:

	rtc@51 {
				compatible = "nxp,pcf2129";

This board defines multiple external RTCs without a complete set of aliases,
leading to unpredictable rtc0/rtc2 index assignment.

A race condition between module probes will swap these indices unpredictably,
which can break system time initialization (since CONFIG_RTC_HCTOSYS_DEVICE
defaults to rtc0) or suspend/resume wakeup functionality.

Could these other boards also be updated with explicit RTC aliases to prevent
the same issue?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260914-b4_imx91_93_rtc-v1-0-daed1cba0714@oss.nxp.com?part=2

Re: [PATCH 0/2] arm64: dts: imx91/imx93: add rtc1 alias for external PCF2131 RTC

[Frank.Li]

From: Frank Li <Frank.Li@nxp.com>


On Mon, 14 Sep 2026 11:21:06 +0800, Joy Zou wrote:
> Only rtc0 was aliased to the internal bbnsm_rtc, while the external
> PCF2131 RTC had no fixed index. When both RTC drivers are built as
> modules, the pcf2131 may probe first and take rtc0, pushing bbnsm_rtc
> to rtc1. Since suspend/resume wakeup relies on the internal bbnsm RTC
> being rtc0, this broke wakeup.
> 
> Add an rtc1 alias for the PCF2131 on the i.MX91 and i.MX93 EVK/QSB
> boards, so the external RTC keeps a fixed index while bbnsm_rtc always
> stays rtc0.
> 
> [...]

Applied, thanks!

[1/2] arm64: dts: imx91-evk/qsb: add rtc1 alias for external PCF2131 RTC
      commit: 92fd18d609ff13e27ab9d19c4764633acde593ec
[2/2] arm64: dts: imx93-evk/qsb: add rtc1 alias for external PCF2131 RTC
      commit: fa7d47a05b464c5ec3af39ebd06b8b73abaa42ff

Best regards,
-- 
Frank Li <Frank.Li@nxp.com>