[PATCH v3 0/4] firmware: raspberrypi: Add support for the tryboot mode

[PATCH v3 0/4] firmware: raspberrypi: Add support for the tryboot mode

[Gregor Herburger]

This adds support for the tryboot mode on Raspberry Pis. As there is no
documentation other than the downstream implementation [0] the
implementation is based on this.

I tested this on Raspberry Pi 5 and therefore I only added the
properties to this devicetree. But afaik this should work on all
Raspberry Pis. I will add it to the correspondings dts if I get some
hardware to test it.

[0] https://github.com/raspberrypi/linux/commit/eb56da0c1925c07e8929ce4c9fe8aeafa7cb8c7b

---
Changes in v3:
- fix use-after-free error by using devm_add_action_or_reset
- ensure endianness of magic byte
- refactor reboot mode registration into separate function
- Link to v2: https://patch.msgid.link/20260630-rpi-tryboot-v2-0-f68d2dc6aa27@linutronix.de

Changes in v2:
- Remove unnecessary reboot_mode_unregister().
- dt-binding: restrict to mode-{normal,tryboot} and only allow 32bit value.
- Link to v1: https://patch.msgid.link/20260626-rpi-tryboot-v1-0-490b1c4c4970@linutronix.de

---
Gregor Herburger (4):
      firmware: raspberrypi: reorder rpi_firmware_property_tag enum
      dt-bindings: raspberrypi,bcm2835-firmware: Include 'reboot-mode.yaml'
      firmware: raspberrypi: Add reboot mode support
      arm64: dts: broadcom: bcm2712: Add reboot modes to firmware node

 .../arm/bcm/raspberrypi,bcm2835-firmware.yaml      |  9 +++++
 .../boot/dts/broadcom/bcm2712-rpi-5-b-base.dtsi    |  2 ++
 drivers/firmware/Kconfig                           |  2 ++
 drivers/firmware/raspberrypi.c                     | 40 +++++++++++++++++++---
 include/soc/bcm2835/raspberrypi-firmware.h         | 22 ++++++------
 5 files changed, 60 insertions(+), 15 deletions(-)
---
base-commit: 8cd9520d35a6c38db6567e97dd93b1f11f185dc6
change-id: 20260623-rpi-tryboot-4292c92b0727

Best regards,
--  
Gregor Herburger <gregor.herburger@linutronix.de>

[PATCH v3 1/4] firmware: raspberrypi: reorder rpi_firmware_property_tag enum

[Gregor Herburger]

The enum was once ordered by tag values. The later added tags were added
in a different order. Reorder the tags again.

No functional change intended.

Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
---
 include/soc/bcm2835/raspberrypi-firmware.h | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index e1f87fbfe5542..66cc5a426c3c5 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -72,26 +72,26 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_GET_EDID_BLOCK =                         0x00030020,
 	RPI_FIRMWARE_GET_CUSTOMER_OTP =                       0x00030021,
 	RPI_FIRMWARE_GET_DOMAIN_STATE =                       0x00030030,
+	RPI_FIRMWARE_GET_GPIO_STATE =                         0x00030041,
+	RPI_FIRMWARE_GET_GPIO_CONFIG =                        0x00030043,
+	RPI_FIRMWARE_GET_PERIPH_REG =                         0x00030045,
 	RPI_FIRMWARE_GET_THROTTLED =                          0x00030046,
 	RPI_FIRMWARE_GET_CLOCK_MEASURED =                     0x00030047,
 	RPI_FIRMWARE_NOTIFY_REBOOT =                          0x00030048,
+	RPI_FIRMWARE_GET_POE_HAT_VAL =                        0x00030049,
+	RPI_FIRMWARE_SET_POE_HAT_VAL =                        0x00030050,
+	RPI_FIRMWARE_NOTIFY_XHCI_RESET =                      0x00030058,
+	RPI_FIRMWARE_NOTIFY_DISPLAY_DONE =                    0x00030066,
 	RPI_FIRMWARE_SET_CLOCK_STATE =                        0x00038001,
 	RPI_FIRMWARE_SET_CLOCK_RATE =                         0x00038002,
 	RPI_FIRMWARE_SET_VOLTAGE =                            0x00038003,
 	RPI_FIRMWARE_SET_TURBO =                              0x00038009,
 	RPI_FIRMWARE_SET_CUSTOMER_OTP =                       0x00038021,
 	RPI_FIRMWARE_SET_DOMAIN_STATE =                       0x00038030,
-	RPI_FIRMWARE_GET_GPIO_STATE =                         0x00030041,
 	RPI_FIRMWARE_SET_GPIO_STATE =                         0x00038041,
 	RPI_FIRMWARE_SET_SDHOST_CLOCK =                       0x00038042,
-	RPI_FIRMWARE_GET_GPIO_CONFIG =                        0x00030043,
 	RPI_FIRMWARE_SET_GPIO_CONFIG =                        0x00038043,
-	RPI_FIRMWARE_GET_PERIPH_REG =                         0x00030045,
 	RPI_FIRMWARE_SET_PERIPH_REG =                         0x00038045,
-	RPI_FIRMWARE_GET_POE_HAT_VAL =                        0x00030049,
-	RPI_FIRMWARE_SET_POE_HAT_VAL =                        0x00030050,
-	RPI_FIRMWARE_NOTIFY_XHCI_RESET =                      0x00030058,
-	RPI_FIRMWARE_NOTIFY_DISPLAY_DONE =                    0x00030066,
 
 	/* Dispmanx TAGS */
 	RPI_FIRMWARE_FRAMEBUFFER_ALLOCATE =                   0x00040001,
@@ -107,7 +107,6 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_FRAMEBUFFER_GET_PALETTE =                0x0004000b,
 	RPI_FIRMWARE_FRAMEBUFFER_GET_TOUCHBUF =               0x0004000f,
 	RPI_FIRMWARE_FRAMEBUFFER_GET_GPIOVIRTBUF =            0x00040010,
-	RPI_FIRMWARE_FRAMEBUFFER_RELEASE =                    0x00048001,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_PHYSICAL_WIDTH_HEIGHT = 0x00044003,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_VIRTUAL_WIDTH_HEIGHT =  0x00044004,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_DEPTH =                 0x00044005,
@@ -117,6 +116,7 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_OVERSCAN =              0x0004400a,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_PALETTE =               0x0004400b,
 	RPI_FIRMWARE_FRAMEBUFFER_TEST_VSYNC =                 0x0004400e,
+	RPI_FIRMWARE_FRAMEBUFFER_RELEASE =                    0x00048001,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_PHYSICAL_WIDTH_HEIGHT =  0x00048003,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_VIRTUAL_WIDTH_HEIGHT =   0x00048004,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_DEPTH =                  0x00048005,
@@ -125,10 +125,10 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_FRAMEBUFFER_SET_VIRTUAL_OFFSET =         0x00048009,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_OVERSCAN =               0x0004800a,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_PALETTE =                0x0004800b,
-	RPI_FIRMWARE_FRAMEBUFFER_SET_TOUCHBUF =               0x0004801f,
-	RPI_FIRMWARE_FRAMEBUFFER_SET_GPIOVIRTBUF =            0x00048020,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_VSYNC =                  0x0004800e,
 	RPI_FIRMWARE_FRAMEBUFFER_SET_BACKLIGHT =              0x0004800f,
+	RPI_FIRMWARE_FRAMEBUFFER_SET_TOUCHBUF =               0x0004801f,
+	RPI_FIRMWARE_FRAMEBUFFER_SET_GPIOVIRTBUF =            0x00048020,
 
 	RPI_FIRMWARE_VCHIQ_INIT =                             0x00048010,
 

-- 
2.47.3

[PATCH v3 2/4] dt-bindings: raspberrypi,bcm2835-firmware: Include 'reboot-mode.yaml'

[Gregor Herburger]

The Raspberry Pi firmware allows to set a reboot mode called tryboot
that allows to try booting from a different partition to allow updating
of the boot partition. Allow reboot mode properties by referencing the
reboot-mode schema. The firmware allows a 32bit value to be sent as
reboot flag so restrict the maxItems to 1.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
---
 .../bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml           | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml b/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml
index 983ea80eaec97..28c5713860468 100644
--- a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml
+++ b/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.yaml
@@ -133,6 +133,15 @@ properties:
     required:
       - compatible
 
+  mode-normal:
+    maxItems: 1
+
+  mode-tryboot:
+    maxItems: 1
+
+allOf:
+  - $ref: /schemas/power/reset/reboot-mode.yaml#
+
 required:
   - compatible
   - mboxes

-- 
2.47.3

[PATCH v3 3/4] firmware: raspberrypi: Add reboot mode support

[Gregor Herburger]

The Raspberry Pi firmware has a tryboot mode where it tries to boot from
another partition. This can be used to create a A/B update scheme.

To enable this on the next boot, the RPI_FIRMWARE_SET_REBOOT_FLAGS
message must be sent to the firmware. Add support for this by
registering a reboot mode driver.

Furthermore, safely registering the reboot mode requires adjusting the
teardown sequence. Replace the manually called rpi_firmware_put() with a
devres-managed called (devm_add_action_or_reset). Without this, the
cleanup function of devm_reboot_mode_register() would trigger a
use-after-free error by attempting to access the firmware context after
it had already been freed by rpi_firmware_remove().

Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
---
 drivers/firmware/Kconfig                   |  2 ++
 drivers/firmware/raspberrypi.c             | 40 ++++++++++++++++++++++++++----
 include/soc/bcm2835/raspberrypi-firmware.h |  2 ++
 3 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
index bbd2155d84838..34605bf7c9734 100644
--- a/drivers/firmware/Kconfig
+++ b/drivers/firmware/Kconfig
@@ -115,6 +115,8 @@ config ISCSI_IBFT
 config RASPBERRYPI_FIRMWARE
 	tristate "Raspberry Pi Firmware Driver"
 	depends on BCM2835_MBOX
+	select POWER_RESET
+	select REBOOT_MODE
 	help
 	  This option enables support for communicating with the firmware on the
 	  Raspberry Pi.
diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
index 0aa322e9a2e73..2a0c40b8052e5 100644
--- a/drivers/firmware/raspberrypi.c
+++ b/drivers/firmware/raspberrypi.c
@@ -14,6 +14,7 @@
 #include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/reboot-mode.h>
 #include <linux/slab.h>
 #include <soc/bcm2835/raspberrypi-firmware.h>
 
@@ -29,6 +30,7 @@ struct rpi_firmware {
 	struct mbox_client cl;
 	struct mbox_chan *chan; /* The property channel. */
 	struct completion c;
+	struct reboot_mode_driver reboot_mode;
 	u32 enabled;
 
 	struct kref consumers;
@@ -273,10 +275,37 @@ static void devm_rpi_firmware_put(void *data)
 	rpi_firmware_put(fw);
 }
 
+static int rpi_firmware_reboot_mode_write(struct reboot_mode_driver *reboot,
+					  unsigned int magic)
+{
+	struct rpi_firmware *fw = container_of(reboot, struct rpi_firmware,
+					       reboot_mode);
+	__le32 fw_magic = cpu_to_le32(magic);
+
+	if (!magic)
+		return 0;
+
+	return rpi_firmware_property(fw, RPI_FIRMWARE_SET_REBOOT_FLAGS,
+				     &fw_magic, sizeof(fw_magic));
+}
+
+static void rpi_register_reboot_mode(struct device *dev, struct rpi_firmware *fw)
+{
+	int ret;
+
+	fw->reboot_mode.dev = dev;
+	fw->reboot_mode.write = rpi_firmware_reboot_mode_write;
+	ret = devm_reboot_mode_register(dev, &fw->reboot_mode);
+	if (ret)
+		dev_err(dev, "Failed to register reboot mode: %d\n", ret);
+
+}
+
 static int rpi_firmware_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct rpi_firmware *fw;
+	int ret;
 
 	/*
 	 * Memory will be freed by rpi_firmware_delete() once all users have
@@ -292,7 +321,7 @@ static int rpi_firmware_probe(struct platform_device *pdev)
 
 	fw->chan = mbox_request_channel(&fw->cl, 0);
 	if (IS_ERR(fw->chan)) {
-		int ret = PTR_ERR(fw->chan);
+		ret = PTR_ERR(fw->chan);
 		kfree(fw);
 		return dev_err_probe(dev, ret, "Failed to get mbox channel\n");
 	}
@@ -302,9 +331,14 @@ static int rpi_firmware_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, fw);
 
+	ret = devm_add_action_or_reset(dev, devm_rpi_firmware_put, fw);
+	if (ret)
+		return ret;
+
 	rpi_firmware_print_firmware_revision(fw);
 	rpi_register_hwmon_driver(dev, fw);
 	rpi_register_clk_driver(dev);
+	rpi_register_reboot_mode(dev, fw);
 
 	return 0;
 }
@@ -321,14 +355,10 @@ static void rpi_firmware_shutdown(struct platform_device *pdev)
 
 static void rpi_firmware_remove(struct platform_device *pdev)
 {
-	struct rpi_firmware *fw = platform_get_drvdata(pdev);
-
 	platform_device_unregister(rpi_hwmon);
 	rpi_hwmon = NULL;
 	platform_device_unregister(rpi_clk);
 	rpi_clk = NULL;
-
-	rpi_firmware_put(fw);
 }
 
 static const struct of_device_id rpi_firmware_of_match[] = {
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index 66cc5a426c3c5..f905bff0fb3ea 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -81,6 +81,7 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_GET_POE_HAT_VAL =                        0x00030049,
 	RPI_FIRMWARE_SET_POE_HAT_VAL =                        0x00030050,
 	RPI_FIRMWARE_NOTIFY_XHCI_RESET =                      0x00030058,
+	RPI_FIRMWARE_GET_REBOOT_FLAGS =                       0x00030064,
 	RPI_FIRMWARE_NOTIFY_DISPLAY_DONE =                    0x00030066,
 	RPI_FIRMWARE_SET_CLOCK_STATE =                        0x00038001,
 	RPI_FIRMWARE_SET_CLOCK_RATE =                         0x00038002,
@@ -92,6 +93,7 @@ enum rpi_firmware_property_tag {
 	RPI_FIRMWARE_SET_SDHOST_CLOCK =                       0x00038042,
 	RPI_FIRMWARE_SET_GPIO_CONFIG =                        0x00038043,
 	RPI_FIRMWARE_SET_PERIPH_REG =                         0x00038045,
+	RPI_FIRMWARE_SET_REBOOT_FLAGS =                       0x00038064,
 
 	/* Dispmanx TAGS */
 	RPI_FIRMWARE_FRAMEBUFFER_ALLOCATE =                   0x00040001,

-- 
2.47.3

[PATCH v3 4/4] arm64: dts: broadcom: bcm2712: Add reboot modes to firmware node

[Gregor Herburger]

The Raspberry Pi firmware driver allows the tryboot reboot mode. Add
this mode and normal boot mode to the node.

Signed-off-by: Gregor Herburger <gregor.herburger@linutronix.de>
---
 arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b-base.dtsi | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b-base.dtsi b/arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b-base.dtsi
index b7a6bc34ae1ab..67095c7ff770d 100644
--- a/arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b-base.dtsi
+++ b/arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b-base.dtsi
@@ -49,6 +49,8 @@ firmware: rpi-firmware {
 			compatible = "raspberrypi,bcm2835-firmware", "simple-mfd";
 
 			mboxes = <&mailbox>;
+			mode-normal = <0>;
+			mode-tryboot = <1>;
 
 			firmware_clocks: clocks {
 				compatible = "raspberrypi,firmware-clocks";

-- 
2.47.3

Re: [PATCH v3 3/4] firmware: raspberrypi: Add reboot mode support

[sashiko-bot]

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

Pre-existing issues:
- [High] TOCTOU race in `rpi_firmware_get` allows `kref_get_unless_zero` to execute on freed memory during concurrent driver unbinding.
--

--- Patch [3]: [PATCH v3 3/4] firmware: raspberrypi: Add reboot mode support ---
commit 0477b96e458c7ecca585d15b527bfef8d16f88fc
Author: Gregor Herburger <gregor.herburger@linutronix.de>
Subject: firmware: raspberrypi: Add reboot mode support

This commit adds tryboot mode support to the Raspberry Pi firmware driver to
enable an A/B update scheme. It registers a reboot mode driver to send the
RPI_FIRMWARE_SET_REBOOT_FLAGS message. Additionally, it transitions the
firmware context teardown to be devres-managed to safely register the reboot
mode.

> diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
> index 0aa322e9a2e73..2a0c40b8052e5 100644
> --- a/drivers/firmware/raspberrypi.c
> +++ b/drivers/firmware/raspberrypi.c
[ ... ]
> @@ -302,9 +331,14 @@ static int rpi_firmware_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, fw);
>  
> +	ret = devm_add_action_or_reset(dev, devm_rpi_firmware_put, fw);
> +	if (ret)
> +		return ret;
> +

[Severity: High]
This is a pre-existing issue, but modifying the teardown sequence brings up a
question about rpi_firmware_get().

Can a concurrent driver unbind and probe trigger a use-after-free in
rpi_firmware_get()?

If a privileged user triggers unbinding, the driver core executes
device_unbind_cleanup(). This calls devres_release_all(), which now triggers
devm_rpi_firmware_put(), dropping the kref to 0 and freeing the fw object.
Crucially, the driver core clears the drvdata after devres_release_all().

If another thread concurrently probes a dependent driver, rpi_firmware_get()
could locklessly read the drvdata pointer before it is cleared:

drivers/firmware/raspberrypi.c:rpi_firmware_get() {
    ...
    fw = platform_get_drvdata(pdev);
    if (!fw)
        goto err_put_device;

    if (!kref_get_unless_zero(&fw->consumers))
        goto err_put_device;
    ...
}

Since fw could already be freed by devm_rpi_firmware_put(), passing it to
kref_get_unless_zero() would access freed memory. Does the retrieval of
drvdata need synchronization to protect against concurrent unbinding?

>  	rpi_firmware_print_firmware_revision(fw);
>  	rpi_register_hwmon_driver(dev, fw);
>  	rpi_register_clk_driver(dev);
> +	rpi_register_reboot_mode(dev, fw);
>  
>  	return 0;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260707-rpi-tryboot-v3-0-fda82fe7ed76@linutronix.de?part=3