[RFC PATCH 0/6] arm64: dts: renesas: add SWDT

[RFC PATCH 0/6] arm64: dts: renesas: add SWDT

[Wolfram Sang]

I forgot over the years why we did not enable the SWDT on R-Car Gen3+.
The reason is that it is used by the firmware on Renesas boards.
However, this was not documented. So, based on a previous discussion
with Geert, here is an RFC how this documentation could look like:

* add the complete node to the SoC DTSI (here only R-Car H3, M3*)
* mark the node as "reserved" for the relevant boards
  (firmware should have done that(tm))

If this approach is acceptable, I'd handle the other SoCs, too, of
course. Looking forward to comments! Passes dtbs_check here BTW.


Wolfram Sang (6):
  arm64: dts: renesas: r8a77951: add SWDT node
  arm64: dts: renesas: r8a77960: add SWDT node
  arm64: dts: renesas: r8a77961: add SWDT node
  arm64: dts: renesas: r8a77965: add SWDT node
  arm64: dts: renesas: salvator-common: mark SWDT as reserved
  arm64: dts: renesas: ulcb: mark SWDT as reserved

 arch/arm64/boot/dts/renesas/r8a77951.dtsi        | 10 ++++++++++
 arch/arm64/boot/dts/renesas/r8a77960.dtsi        | 10 ++++++++++
 arch/arm64/boot/dts/renesas/r8a77961.dtsi        | 10 ++++++++++
 arch/arm64/boot/dts/renesas/r8a77965.dtsi        | 10 ++++++++++
 arch/arm64/boot/dts/renesas/salvator-common.dtsi |  5 +++++
 arch/arm64/boot/dts/renesas/ulcb.dtsi            |  5 +++++
 6 files changed, 50 insertions(+)

-- 
2.47.2

[RFC PATCH 1/6] arm64: dts: renesas: r8a77951: add SWDT node

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 arch/arm64/boot/dts/renesas/r8a77951.dtsi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/r8a77951.dtsi b/arch/arm64/boot/dts/renesas/r8a77951.dtsi
index c389ebc7e6ce..b3e935e5a2b1 100644
--- a/arch/arm64/boot/dts/renesas/r8a77951.dtsi
+++ b/arch/arm64/boot/dts/renesas/r8a77951.dtsi
@@ -365,6 +365,16 @@ rwdt: watchdog@e6020000 {
 			status = "disabled";
 		};
 
+		swdt: watchdog@e6030000 {
+			compatible = "renesas,r8a7795-wdt", "renesas,rcar-gen3-wdt";
+			reg = <0 0xe6030000 0 0x0c>;
+			interrupts = <GIC_SPI 141 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_CORE R8A7795_CLK_OSC>;
+			power-domains = <&sysc R8A7795_PD_ALWAYS_ON>;
+			resets = <&cpg 401>;
+			status = "disabled";
+		};
+
 		gpio0: gpio@e6050000 {
 			compatible = "renesas,gpio-r8a7795",
 				     "renesas,rcar-gen3-gpio";
-- 
2.47.2

[RFC PATCH 2/6] arm64: dts: renesas: r8a77960: add SWDT node

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 arch/arm64/boot/dts/renesas/r8a77960.dtsi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/r8a77960.dtsi b/arch/arm64/boot/dts/renesas/r8a77960.dtsi
index 6d039019905d..2fd08c002a47 100644
--- a/arch/arm64/boot/dts/renesas/r8a77960.dtsi
+++ b/arch/arm64/boot/dts/renesas/r8a77960.dtsi
@@ -330,6 +330,16 @@ rwdt: watchdog@e6020000 {
 			status = "disabled";
 		};
 
+		swdt: watchdog@e6030000 {
+			compatible = "renesas,r8a7796-wdt", "renesas,rcar-gen3-wdt";
+			reg = <0 0xe6030000 0 0x0c>;
+			interrupts = <GIC_SPI 141 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_CORE R8A7796_CLK_OSC>;
+			power-domains = <&sysc R8A7796_PD_ALWAYS_ON>;
+			resets = <&cpg 401>;
+			status = "disabled";
+		};
+
 		gpio0: gpio@e6050000 {
 			compatible = "renesas,gpio-r8a7796",
 				     "renesas,rcar-gen3-gpio";
-- 
2.47.2

[RFC PATCH 3/6] arm64: dts: renesas: r8a77961: add SWDT node

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 arch/arm64/boot/dts/renesas/r8a77961.dtsi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/r8a77961.dtsi b/arch/arm64/boot/dts/renesas/r8a77961.dtsi
index 1637b534fc68..bbfd72705db3 100644
--- a/arch/arm64/boot/dts/renesas/r8a77961.dtsi
+++ b/arch/arm64/boot/dts/renesas/r8a77961.dtsi
@@ -330,6 +330,16 @@ rwdt: watchdog@e6020000 {
 			status = "disabled";
 		};
 
+		swdt: watchdog@e6030000 {
+			compatible = "renesas,r8a77961-wdt", "renesas,rcar-gen3-wdt";
+			reg = <0 0xe6030000 0 0x0c>;
+			interrupts = <GIC_SPI 141 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_CORE R8A77961_CLK_OSC>;
+			power-domains = <&sysc R8A77961_PD_ALWAYS_ON>;
+			resets = <&cpg 401>;
+			status = "disabled";
+		};
+
 		gpio0: gpio@e6050000 {
 			compatible = "renesas,gpio-r8a77961",
 				     "renesas,rcar-gen3-gpio";
-- 
2.47.2

[RFC PATCH 4/6] arm64: dts: renesas: r8a77965: add SWDT node

[Wolfram Sang]

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 arch/arm64/boot/dts/renesas/r8a77965.dtsi | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/r8a77965.dtsi b/arch/arm64/boot/dts/renesas/r8a77965.dtsi
index 353a77187089..2c414179f53c 100644
--- a/arch/arm64/boot/dts/renesas/r8a77965.dtsi
+++ b/arch/arm64/boot/dts/renesas/r8a77965.dtsi
@@ -201,6 +201,16 @@ rwdt: watchdog@e6020000 {
 			status = "disabled";
 		};
 
+		swdt: watchdog@e6030000 {
+			compatible = "renesas,r8a77965-wdt", "renesas,rcar-gen3-wdt";
+			reg = <0 0xe6030000 0 0x0c>;
+			interrupts = <GIC_SPI 141 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&cpg CPG_CORE R8A77965_CLK_OSC>;
+			power-domains = <&sysc R8A77965_PD_ALWAYS_ON>;
+			resets = <&cpg 401>;
+			status = "disabled";
+		};
+
 		gpio0: gpio@e6050000 {
 			compatible = "renesas,gpio-r8a77965",
 				     "renesas,rcar-gen3-gpio";
-- 
2.47.2

[RFC PATCH 5/6] arm64: dts: renesas: salvator-common: mark SWDT as reserved

[Wolfram Sang]

This watchdog can't be used with Linux because the firmware needs it on
Salvator boards. Sadly, it doesn't mark the node as reserved, so this is
added manually here.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 arch/arm64/boot/dts/renesas/salvator-common.dtsi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/salvator-common.dtsi b/arch/arm64/boot/dts/renesas/salvator-common.dtsi
index bbb3583372d0..fa8bfee07b3c 100644
--- a/arch/arm64/boot/dts/renesas/salvator-common.dtsi
+++ b/arch/arm64/boot/dts/renesas/salvator-common.dtsi
@@ -1004,6 +1004,11 @@ &ssi1 {
 	shared-pin;
 };
 
+/* Firmware should reserve it but sadly doesn't */
+&swdt {
+	status = "reserved";
+};
+
 &usb_extal_clk {
 	clock-frequency = <50000000>;
 };
-- 
2.47.2

[RFC PATCH 6/6] arm64: dts: renesas: ulcb: mark SWDT as reserved

[Wolfram Sang]

This watchdog can't be used with Linux because the firmware needs it on
ULCB boards. Sadly, it doesn't mark the node as reserved, so this is
added manually here.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
---
 arch/arm64/boot/dts/renesas/ulcb.dtsi | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/arch/arm64/boot/dts/renesas/ulcb.dtsi b/arch/arm64/boot/dts/renesas/ulcb.dtsi
index 8a30908992ab..a9e53b36f1d9 100644
--- a/arch/arm64/boot/dts/renesas/ulcb.dtsi
+++ b/arch/arm64/boot/dts/renesas/ulcb.dtsi
@@ -495,6 +495,11 @@ &ssi1 {
 	shared-pin;
 };
 
+/* Firmware should reserve it but sadly doesn't */
+&swdt {
+	status = "reserved";
+};
+
 &usb2_phy1 {
 	pinctrl-0 = <&usb1_pins>;
 	pinctrl-names = "default";
-- 
2.47.2

Re: [RFC PATCH 0/6] arm64: dts: renesas: add SWDT

[Geert Uytterhoeven]

Hi Wolfram,

On Sat, 20 Sept 2025 at 08:44, Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> I forgot over the years why we did not enable the SWDT on R-Car Gen3+.
> The reason is that it is used by the firmware on Renesas boards.
> However, this was not documented. So, based on a previous discussion
> with Geert, here is an RFC how this documentation could look like:
>
> * add the complete node to the SoC DTSI (here only R-Car H3, M3*)
> * mark the node as "reserved" for the relevant boards
>   (firmware should have done that(tm))
>
> If this approach is acceptable, I'd handle the other SoCs, too, of
> course. Looking forward to comments! Passes dtbs_check here BTW.
>
> Wolfram Sang (6):
>   arm64: dts: renesas: r8a77951: add SWDT node
>   arm64: dts: renesas: r8a77960: add SWDT node
>   arm64: dts: renesas: r8a77961: add SWDT node
>   arm64: dts: renesas: r8a77965: add SWDT node
>   arm64: dts: renesas: salvator-common: mark SWDT as reserved
>   arm64: dts: renesas: ulcb: mark SWDT as reserved

Thanks for your series!

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds