[PATCH v4 0/3] support Linux reboot modes in syscon-reboot on gs101 (Google Pixel)

[PATCH v4 0/3] support Linux reboot modes in syscon-reboot on gs101 (Google Pixel)

[André Draszik]

This series updates syscon-reboot to support warm/soft and soft/hard
reboot on gs101-based boards (Google Pixel 6 and Pixel 6 Pro).

Linux supports a couple different reboot modes, but syscon-reboot
doesn't distinguish between them and issues the same syscon register
write irrespective of the reboot mode requested by the kernel.

This is a problem when platforms want to do a cold reboot most of the
time, which could e.g. wipe RAM etc, but also want to support rebooting
while keeping RAM contents in certain cases.

On gs101, this can be implemented using different syscon register
writes.

As Rob pointed out in [1], register access shouldn't be encoded into
DT, though. At the same time, at least on gs101, the difference is just
different register values in different registers. Therefore these
patches:

    * add a specific binding for gs101 reset
    * update the generic syscon reset driver to support this new
      compatible 'google,gs101-reboot'. In this case, and as suggested
      in [1], the syscon writes are then deducted from the compatible,
      rather than parsing them from DT.

The existing generic syscon-reboot driver seems like a suitable place
to add support for that, given all of this is straight forward and
simple and similar to the existing code. If the preference is to have a
separate driver copying much of the existing generic syscon-reboot
driver code instead, please let me know.

Link: https://lore.kernel.org/all/20250227132644.GA1924628-robh@kernel.org/ [1]

Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
Changes in v4:
- Rob:
  - don't add more properties to existing 'syscon-reboot' compatible /
    binding
  - add specific binding for 'google,gs101-reboot' compatible and
    related driver changes
- Link to v3: https://lore.kernel.org/r/20250227-syscon-reboot-reset-mode-v3-0-959ac53c338a@linaro.org

Changes in v3:
- support <reset-mode>-reg in driver, not just in binding, doh...
- correctly parse <reset-mode>-offset
- add a comment for all the BUILD_BUG_ON() checks
- Link to v2: https://lore.kernel.org/r/20250226-syscon-reboot-reset-mode-v2-0-f80886370bb7@linaro.org

Changes in v2:
- fix whitespace issues in binding
- Link to v1: https://lore.kernel.org/r/20250226-syscon-reboot-reset-mode-v1-0-91c1b62166ae@linaro.org

---
André Draszik (3):
      dt-bindings: power: reset: google,gs101-reboot: add Google GS101 specific reset
      dt-bindings: soc: samsung: exynos-pmu: update reset for gs101
      power: reset: syscon-reboot: add gs101-specific reset

 .../bindings/power/reset/google,gs101-reboot.yaml  | 32 +++++++
 .../bindings/soc/samsung/exynos-pmu.yaml           | 21 +++++
 MAINTAINERS                                        |  1 +
 drivers/power/reset/syscon-reboot.c                | 98 +++++++++++++++++-----
 4 files changed, 131 insertions(+), 21 deletions(-)
---
base-commit: db8da9da41bced445077925f8a886c776a47440c
change-id: 20250226-syscon-reboot-reset-mode-566588b847e1

Best regards,
-- 
André Draszik <andre.draszik@linaro.org>

[PATCH v4 1/3] dt-bindings: power: reset: google,gs101-reboot: add Google GS101 specific reset

[André Draszik]

GS101 supports a couple different reset types via certain registers in
the SYSCON register map.

Add a binding for this.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
 .../bindings/power/reset/google,gs101-reboot.yaml  | 32 ++++++++++++++++++++++
 MAINTAINERS                                        |  1 +
 2 files changed, 33 insertions(+)

diff --git a/Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml b/Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml
new file mode 100644
index 0000000000000000000000000000000000000000..cbd0a1d9b45af0cb994d616c56b96440c43ab971
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml
@@ -0,0 +1,32 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/power/reset/google,gs101-reboot.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Google GS101 syscon-mapped reset
+
+maintainers:
+  - André Draszik <andre.draszik@linaro.org>
+
+description:
+  GS101 supports a couple different reset types via certain registers in the
+  SYSCON register map. This map is retrieved from the parental dt-node. So the
+  gs101-reboot node should be represented as a sub-node of such a node.
+
+properties:
+  compatible:
+    oneOf:
+      - items:
+          - const: google,gs101-reboot
+
+  priority:
+    default: 192
+
+required:
+  - compatible
+
+additionalProperties: false
+
+allOf:
+  - $ref: restart-handler.yaml#
diff --git a/MAINTAINERS b/MAINTAINERS
index 322ee00547f6e494a96d2495092f72148da22bd0..e27f5e672bc5a04777afd098355898654654659d 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -10080,6 +10080,7 @@ L:	linux-samsung-soc@vger.kernel.org
 S:	Maintained
 C:	irc://irc.oftc.net/pixel6-kernel-dev
 F:	Documentation/devicetree/bindings/clock/google,gs101-clock.yaml
+F:	Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml
 F:	arch/arm64/boot/dts/exynos/google/
 F:	drivers/clk/samsung/clk-gs101.c
 F:	drivers/phy/samsung/phy-gs101-ufs.c

-- 
2.49.0.472.ge94155a9ec-goog

[PATCH v4 2/3] dt-bindings: soc: samsung: exynos-pmu: update reset for gs101

[André Draszik]

Add the gs101-specific reset node, allow it on gs101, and disallow it
on !gs101. Similarly, disallow the generic 'syscon-reboot' on gs101, as
we want the specific one in that case.

Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
 .../devicetree/bindings/soc/samsung/exynos-pmu.yaml | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml
index 204da6fe458d2d4bfeee1471ebc5c38247477ae2..8c7362cf3eeab11f6bb13a27eb295d5ee6721b71 100644
--- a/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml
+++ b/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml
@@ -97,6 +97,12 @@ properties:
     $ref: /schemas/phy/samsung,dp-video-phy.yaml
     unevaluatedProperties: false
 
+  gs101-reboot:
+    $ref: /schemas/power/reset/google,gs101-reboot.yaml#
+    type: object
+    description:
+      Node for gs101-specific reboot method
+
   interrupt-controller:
     description:
       Some PMUs are capable of behaving as an interrupt controller (mostly
@@ -136,6 +142,21 @@ required:
 additionalProperties: false
 
 allOf:
+  - if:
+      properties:
+        compatible:
+          contains:
+            const: google,gs101-pmu
+    then:
+      properties:
+        gs101-reboot: true
+        syscon-reboot: false
+
+    else:
+      properties:
+        gs101-reboot: false
+        syscon-reboot: true
+
   - if:
       properties:
         compatible:

-- 
2.49.0.472.ge94155a9ec-goog

[PATCH v4 3/3] power: reset: syscon-reboot: add gs101-specific reset

[André Draszik]

Linux supports a couple different reset modes, but this driver here
doesn't distinguish between them and issues the same syscon register
write irrespective of the reset mode requested by the kernel.

Since DTs should not encode register writes (see e.g. [1]), update this
driver to support different reset modes based on DT compatible match.

At the same time, add support for Google GS101, which does support
cold, hard, warm, and soft.

As an example why this is useful, other than properly supporting the
Linux reboot= kernel command line option or sysfs entry, this change
allows gs101-platforms to default to a more secure cold-reset, but also
to warm-reset in case RAM contents needs to be retained across the
reset.

Link: https://lore.kernel.org/all/20250227132644.GA1924628-robh@kernel.org/ [1]
Signed-off-by: André Draszik <andre.draszik@linaro.org>
---
 drivers/power/reset/syscon-reboot.c | 98 +++++++++++++++++++++++++++++--------
 1 file changed, 77 insertions(+), 21 deletions(-)

diff --git a/drivers/power/reset/syscon-reboot.c b/drivers/power/reset/syscon-reboot.c
index d623d77e657e4c233d8ae88bb099bee13c48a9ef..2e2cf5f62d733c7c07110f3052583607e25afd5d 100644
--- a/drivers/power/reset/syscon-reboot.c
+++ b/drivers/power/reset/syscon-reboot.c
@@ -14,11 +14,24 @@
 #include <linux/reboot.h>
 #include <linux/regmap.h>
 
-struct syscon_reboot_context {
-	struct regmap *map;
+struct reboot_mode_bits {
 	u32 offset;
-	u32 value;
 	u32 mask;
+	u32 value;
+	bool valid;
+};
+
+struct reboot_data {
+	struct reboot_mode_bits mode_bits[REBOOT_SOFT + 1];
+	struct reboot_mode_bits catchall;
+};
+
+struct syscon_reboot_context {
+	struct regmap *map;
+
+	const struct reboot_data *rd; /* from of match data, if any */
+	struct reboot_mode_bits catchall; /* from DT */
+
 	struct notifier_block restart_handler;
 };
 
@@ -28,9 +41,21 @@ static int syscon_restart_handle(struct notifier_block *this,
 	struct syscon_reboot_context *ctx =
 			container_of(this, struct syscon_reboot_context,
 					restart_handler);
+	const struct reboot_mode_bits *mode_bits;
+
+	if (ctx->rd) {
+		if (mode < ARRAY_SIZE(ctx->rd->mode_bits) &&
+		    ctx->rd->mode_bits[mode].valid)
+			mode_bits = &ctx->rd->mode_bits[mode];
+		else
+			mode_bits = &ctx->rd->catchall;
+	} else {
+		mode_bits = &ctx->catchall;
+	}
 
 	/* Issue the reboot */
-	regmap_update_bits(ctx->map, ctx->offset, ctx->mask, ctx->value);
+	regmap_update_bits(ctx->map, mode_bits->offset, mode_bits->mask,
+			   mode_bits->value);
 
 	mdelay(1000);
 
@@ -42,7 +67,6 @@ static int syscon_reboot_probe(struct platform_device *pdev)
 {
 	struct syscon_reboot_context *ctx;
 	struct device *dev = &pdev->dev;
-	int mask_err, value_err;
 	int priority;
 	int err;
 
@@ -60,24 +84,33 @@ static int syscon_reboot_probe(struct platform_device *pdev)
 	if (of_property_read_s32(pdev->dev.of_node, "priority", &priority))
 		priority = 192;
 
-	if (of_property_read_u32(pdev->dev.of_node, "offset", &ctx->offset))
-		if (of_property_read_u32(pdev->dev.of_node, "reg", &ctx->offset))
-			return -EINVAL;
+	ctx->rd = of_device_get_match_data(dev);
+	if (!ctx->rd) {
+		int mask_err, value_err;
 
-	value_err = of_property_read_u32(pdev->dev.of_node, "value", &ctx->value);
-	mask_err = of_property_read_u32(pdev->dev.of_node, "mask", &ctx->mask);
-	if (value_err && mask_err) {
-		dev_err(dev, "unable to read 'value' and 'mask'");
-		return -EINVAL;
-	}
+		if (of_property_read_u32(pdev->dev.of_node, "offset",
+					 &ctx->catchall.offset) &&
+		    of_property_read_u32(pdev->dev.of_node, "reg",
+					 &ctx->catchall.offset))
+			return -EINVAL;
 
-	if (value_err) {
-		/* support old binding */
-		ctx->value = ctx->mask;
-		ctx->mask = 0xFFFFFFFF;
-	} else if (mask_err) {
-		/* support value without mask*/
-		ctx->mask = 0xFFFFFFFF;
+		value_err = of_property_read_u32(pdev->dev.of_node, "value",
+						 &ctx->catchall.value);
+		mask_err = of_property_read_u32(pdev->dev.of_node, "mask",
+						&ctx->catchall.mask);
+		if (value_err && mask_err) {
+			dev_err(dev, "unable to read 'value' and 'mask'");
+			return -EINVAL;
+		}
+
+		if (value_err) {
+			/* support old binding */
+			ctx->catchall.value = ctx->catchall.mask;
+			ctx->catchall.mask = 0xFFFFFFFF;
+		} else if (mask_err) {
+			/* support value without mask */
+			ctx->catchall.mask = 0xFFFFFFFF;
+		}
 	}
 
 	ctx->restart_handler.notifier_call = syscon_restart_handle;
@@ -89,7 +122,30 @@ static int syscon_reboot_probe(struct platform_device *pdev)
 	return err;
 }
 
+static const struct reboot_data gs101_reboot_data = {
+	.mode_bits = {
+		[REBOOT_WARM] = {
+			.offset = 0x3a00, /* SYSTEM_CONFIGURATION */
+			.mask = 0x00000002, /* SWRESET_SYSTEM */
+			.value = 0x00000002,
+			.valid = true,
+		},
+		[REBOOT_SOFT] = {
+			.offset = 0x3a00, /* SYSTEM_CONFIGURATION */
+			.mask = 0x00000002, /* SWRESET_SYSTEM */
+			.value = 0x00000002,
+			.valid = true,
+		},
+	},
+	.catchall = {
+		.offset = 0x3e9c, /* PAD_CTRL_PWR_HOLD */
+		.mask = 0x00000100,
+		.value = 0x00000000,
+	},
+};
+
 static const struct of_device_id syscon_reboot_of_match[] = {
+	{ .compatible = "google,gs101-reboot", .data = &gs101_reboot_data  },
 	{ .compatible = "syscon-reboot" },
 	{}
 };

-- 
2.49.0.472.ge94155a9ec-goog

Re: [PATCH v4 1/3] dt-bindings: power: reset: google,gs101-reboot: add Google GS101 specific reset

[Krzysztof Kozlowski]

On Fri, Mar 28, 2025 at 03:15:19PM +0000, André Draszik wrote:
> GS101 supports a couple different reset types via certain registers in
> the SYSCON register map.
> 
> Add a binding for this.
> 
> Signed-off-by: André Draszik <andre.draszik@linaro.org>
> ---
>  .../bindings/power/reset/google,gs101-reboot.yaml  | 32 ++++++++++++++++++++++
>  MAINTAINERS                                        |  1 +
>  2 files changed, 33 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml b/Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml
> new file mode 100644
> index 0000000000000000000000000000000000000000..cbd0a1d9b45af0cb994d616c56b96440c43ab971
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/reset/google,gs101-reboot.yaml
> @@ -0,0 +1,32 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/power/reset/google,gs101-reboot.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Google GS101 syscon-mapped reset
> +
> +maintainers:
> +  - André Draszik <andre.draszik@linaro.org>
> +
> +description:
> +  GS101 supports a couple different reset types via certain registers in the
> +  SYSCON register map. This map is retrieved from the parental dt-node. So the
> +  gs101-reboot node should be represented as a sub-node of such a node.
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:

Just const instead of these two


> +          - const: google,gs101-reboot
> +
> +  priority:
> +    default: 192
> +
> +required:
> +  - compatible
> +
> +additionalProperties: false
> +
> +allOf:
> +  - $ref: restart-handler.yaml#

Missing example... unless you are adding it in the other patch to the
parent node. but then separate schema for just two properties and allOf:
is really too much. Altough let me comment on the other patch.

Best regards,
Krzysztof

Re: [PATCH v4 2/3] dt-bindings: soc: samsung: exynos-pmu: update reset for gs101

[Krzysztof Kozlowski]

On Fri, Mar 28, 2025 at 03:15:20PM +0000, André Draszik wrote:
> Add the gs101-specific reset node, allow it on gs101, and disallow it
> on !gs101. Similarly, disallow the generic 'syscon-reboot' on gs101, as
> we want the specific one in that case.
> 
> Signed-off-by: André Draszik <andre.draszik@linaro.org>
> ---
>  .../devicetree/bindings/soc/samsung/exynos-pmu.yaml | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml b/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml
> index 204da6fe458d2d4bfeee1471ebc5c38247477ae2..8c7362cf3eeab11f6bb13a27eb295d5ee6721b71 100644
> --- a/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml
> +++ b/Documentation/devicetree/bindings/soc/samsung/exynos-pmu.yaml
> @@ -97,6 +97,12 @@ properties:
>      $ref: /schemas/phy/samsung,dp-video-phy.yaml
>      unevaluatedProperties: false
>  
> +  gs101-reboot:

syscon-reboot

> +    $ref: /schemas/power/reset/google,gs101-reboot.yaml#

... which leads us to the existing node. Just use oneOf:

oneOf:
  - $ref: /schemas/power/reset/syscon-reboot.yaml#
  - $ref: /schemas/power/reset/google,gs101-reboot.yaml#

or actually better:

additionalProperties: true
properties:
  compatible:
    enum:
      - syscon-reboot
      - google,gs101-reboot

Best regards,
Krzysztof