diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c
index a200a2174611..a13558154ac3 100644
--- a/drivers/firmware/raspberrypi.c
+++ b/drivers/firmware/raspberrypi.c
@@ -1,12 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Defines interfaces for interacting wtih the Raspberry Pi firmware's
  * property channel.
  *
  * Copyright © 2015 Broadcom
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 
 #include <linux/dma-mapping.h>
@@ -14,6 +11,7 @@
 #include <linux/module.h>
 #include <linux/of_platform.h>
 #include <linux/platform_device.h>
+#include <linux/slab.h>
 #include <soc/bcm2835/raspberrypi-firmware.h>
 
 #define MBOX_MSG(chan, data28)		(((data28) & ~0xf) | ((chan) & 0xf))
@@ -21,8 +19,6 @@
 #define MBOX_DATA28(msg)		((msg) & ~0xf)
 #define MBOX_CHAN_PROPERTY		8
 
-#define MAX_RPI_FW_PROP_BUF_SIZE	32
-
 static struct platform_device *rpi_hwmon;
 
 struct rpi_firmware {
@@ -56,8 +52,12 @@ rpi_firmware_transaction(struct rpi_firmware *fw, u32 chan, u32 data)
 	reinit_completion(&fw->c);
 	ret = mbox_send_message(fw->chan, &message);
 	if (ret >= 0) {
-		wait_for_completion(&fw->c);
-		ret = 0;
+		if (wait_for_completion_timeout(&fw->c, HZ)) {
+			ret = 0;
+		} else {
+			ret = -ETIMEDOUT;
+			WARN_ONCE(1, "Firmware transaction timeout");
+		}
 	} else {
 		dev_err(fw->cl.dev, "mbox_send_message returned %d\n", ret);
 	}
@@ -144,28 +144,30 @@ EXPORT_SYMBOL_GPL(rpi_firmware_property_list);
 int rpi_firmware_property(struct rpi_firmware *fw,
 			  u32 tag, void *tag_data, size_t buf_size)
 {
-	/* Single tags are very small (generally 8 bytes), so the
-	 * stack should be safe.
-	 */
-	u8 data[sizeof(struct rpi_firmware_property_tag_header) +
-		MAX_RPI_FW_PROP_BUF_SIZE];
-	struct rpi_firmware_property_tag_header *header =
-		(struct rpi_firmware_property_tag_header *)data;
+	struct rpi_firmware_property_tag_header *header;
 	int ret;
 
-	if (WARN_ON(buf_size > sizeof(data) - sizeof(*header)))
-		return -EINVAL;
+	/* Some mailboxes can use over 1k bytes. Rather than checking
+	 * size and using stack or kmalloc depending on requirements,
+	 * just use kmalloc. Mailboxes don't get called enough to worry
+	 * too much about the time taken in the allocation.
+	 */
+	void *data = kmalloc(sizeof(*header) + buf_size, GFP_KERNEL);
 
+	if (!data)
+		return -ENOMEM;
+
+	header = data;
 	header->tag = tag;
 	header->buf_size = buf_size;
 	header->req_resp_size = 0;
-	memcpy(data + sizeof(struct rpi_firmware_property_tag_header),
-	       tag_data, buf_size);
+	memcpy(data + sizeof(*header), tag_data, buf_size);
 
-	ret = rpi_firmware_property_list(fw, &data, buf_size + sizeof(*header));
-	memcpy(tag_data,
-	       data + sizeof(struct rpi_firmware_property_tag_header),
-	       buf_size);
+	ret = rpi_firmware_property_list(fw, data, buf_size + sizeof(*header));
+
+	memcpy(tag_data, data + sizeof(*header), buf_size);
+
+	kfree(data);
 
 	return ret;
 }
diff --git a/drivers/soc/bcm/raspberrypi-power.c b/drivers/soc/bcm/raspberrypi-power.c
index a78dfe0a2b50..5d1aacdd84ef 100644
--- a/drivers/soc/bcm/raspberrypi-power.c
+++ b/drivers/soc/bcm/raspberrypi-power.c
@@ -1,8 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
 /* (C) 2015 Pengutronix, Alexander Aring <aar@pengutronix.de>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  *
  * Authors:
  * Alexander Aring <aar@pengutronix.de>
diff --git a/include/dt-bindings/power/raspberrypi-power.h b/include/dt-bindings/power/raspberrypi-power.h
index b3ff8e09a78f..3575f9f4b0bd 100644
--- a/include/dt-bindings/power/raspberrypi-power.h
+++ b/include/dt-bindings/power/raspberrypi-power.h
@@ -1,9 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  *  Copyright © 2015 Broadcom
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 
 #ifndef _DT_BINDINGS_ARM_BCM2835_RPI_POWER_H
diff --git a/include/soc/bcm2835/raspberrypi-firmware.h b/include/soc/bcm2835/raspberrypi-firmware.h
index c4a5c9e9fb47..4be1aa4435ae 100644
--- a/include/soc/bcm2835/raspberrypi-firmware.h
+++ b/include/soc/bcm2835/raspberrypi-firmware.h
@@ -1,9 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  *  Copyright © 2015 Broadcom
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
  */
 
 #ifndef __SOC_RASPBERRY_FIRMWARE_H__