Re: [PATCH v20 06/10] power: reset: Add psci-reboot-mode driver
From: Shivendra Pratap
Date: Tue Mar 31 2026 - 14:09:17 EST
On 27-03-2026 19:25, Lorenzo Pieralisi wrote:
On Wed, Mar 04, 2026 at 11:33:06PM +0530, Shivendra Pratap wrote:
PSCI supports different types of resets like COLD reset, ARCH WARM
reset, vendor-specific resets. Currently there is no common driver that
handles all supported psci resets at one place. Additionally, there is
no common mechanism to issue the supported psci resets from userspace.
Add a PSCI reboot mode driver and define two types of PSCI resets in the
driver as reboot-modes: predefined resets controlled by Linux
reboot_mode and customizable resets defined by SoC vendors in their
device tree under the psci:reboot-mode node.
Register the driver with the reboot-mode framework to interface these
resets to userspace. When userspace initiates a supported command, pass
the reset arguments to the PSCI driver to enable command-based reset.
This change allows userspace to issue supported PSCI reset commands
using the standard reboot system calls while enabling SoC vendors to
define their specific resets for PSCI.
Signed-off-by: Shivendra Pratap <shivendra.pratap@xxxxxxxxxxxxxxxx>
---
drivers/power/reset/Kconfig | 10 +++
drivers/power/reset/Makefile | 1 +
drivers/power/reset/psci-reboot-mode.c | 119 +++++++++++++++++++++++++++++++++
3 files changed, 130 insertions(+)
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index f6c1bcbb57deff3568d6b1b326454add3b3bbf06..529d6c7d3555601f7b7e6199acd29838030fcef2 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -348,6 +348,16 @@ config NVMEM_REBOOT_MODE
then the bootloader can read it and take different
action according to the mode.
+config PSCI_REBOOT_MODE
+ bool "PSCI reboot mode driver"
+ depends on OF && ARM_PSCI_FW
+ select REBOOT_MODE
+ help
+ Say y here will enable PSCI reboot mode driver. This gets
+ the PSCI reboot mode arguments and passes them to psci
+ driver. psci driver uses these arguments for issuing
+ device reset into different boot states.
+
config POWER_MLXBF
tristate "Mellanox BlueField power handling driver"
depends on (GPIO_MLXBF2 || GPIO_MLXBF3) && ACPI
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 0e4ae6f6b5c55729cf60846d47e6fe0fec24f3cc..49774b42cdf61fd57a5b70f286c65c9d66bbc0cb 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -40,4 +40,5 @@ obj-$(CONFIG_REBOOT_MODE) += reboot-mode.o
obj-$(CONFIG_SYSCON_REBOOT_MODE) += syscon-reboot-mode.o
obj-$(CONFIG_POWER_RESET_SC27XX) += sc27xx-poweroff.o
obj-$(CONFIG_NVMEM_REBOOT_MODE) += nvmem-reboot-mode.o
+obj-$(CONFIG_PSCI_REBOOT_MODE) += psci-reboot-mode.o
obj-$(CONFIG_POWER_MLXBF) += pwr-mlxbf.o
diff --git a/drivers/power/reset/psci-reboot-mode.c b/drivers/power/reset/psci-reboot-mode.c
new file mode 100644
index 0000000000000000000000000000000000000000..86bef195228b0924704c2936b99f6801c14ff1b1
--- /dev/null
+++ b/drivers/power/reset/psci-reboot-mode.c
@@ -0,0 +1,119 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#include <linux/device/faux.h>
+#include <linux/device.h>
Nit: swap the two.
Ack. thanks.
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/psci.h>
+#include <linux/reboot.h>
+#include <linux/reboot-mode.h>
+#include <linux/types.h>
+
+/*
+ * Predefined reboot-modes are defined as per the values
+ * of enum reboot_mode defined in the kernel: reboot.c.
+ */
+static struct mode_info psci_resets[] = {
+ { .mode = "warm", .magic = REBOOT_WARM},
+ { .mode = "soft", .magic = REBOOT_SOFT},
+ { .mode = "cold", .magic = REBOOT_COLD},
+};
+
+static void psci_reboot_mode_set_predefined_modes(struct reboot_mode_driver *reboot)
+{
+ INIT_LIST_HEAD(&reboot->predefined_modes);
+ for (u32 i = 0; i < ARRAY_SIZE(psci_resets); i++) {
+ /* Prepare the magic with arg1 as 0 and arg2 as per pre-defined mode */
+ psci_resets[i].magic = REBOOT_MODE_MAGIC(0, psci_resets[i].magic);
This looks weird to me, why can't we just initialize the array with the values
directly ?
Ack. The idea was to avoid Typecasting. Will check on this.
+ INIT_LIST_HEAD(&psci_resets[i].list);
+ list_add_tail(&psci_resets[i].list, &reboot->predefined_modes);
+ }
+}
+
+/*
+ * arg1 is reset_type(Low 32 bit of magic).
+ * arg2 is cookie(High 32 bit of magic).
+ * If reset_type is 0, cookie will be used to decide the reset command.
+ */
+static int psci_reboot_mode_write(struct reboot_mode_driver *reboot, u64 magic)
+{
+ u32 reset_type = REBOOT_MODE_ARG1(magic);
+ u32 cookie = REBOOT_MODE_ARG2(magic);
+
+ if (reset_type == 0) {
+ if (cookie == REBOOT_WARM || cookie == REBOOT_SOFT)
+ psci_set_reset_cmd(true, 0, 0);
+ else
+ psci_set_reset_cmd(false, 0, 0);
+ } else {
+ psci_set_reset_cmd(true, reset_type, cookie);
+ }
I don't think that psci_set_reset_cmd() has the right interface (and this
nested if is too complicated for my taste). All we need to pass is reset-type
and cookie (and if the reset is one of the predefined ones, reset-type is 0
and cookie is the REBOOT_* cookie).
Then the PSCI firmware driver will take the action according to what
resets are available.
How does it sound ?
So we mean these checks will move to the psci driver? Sorry for re-iterating the question.
Working on this via MFD. Some issue as again MFD framework does not allows a fwnode based driver registration. Will update.+
+ return NOTIFY_DONE;
+}
+
+static int psci_reboot_mode_register_device(struct faux_device *fdev)
+{
+ struct reboot_mode_driver *reboot;
+ int ret;
+
+ reboot = devm_kzalloc(&fdev->dev, sizeof(*reboot), GFP_KERNEL);
+ if (!reboot)
+ return -ENOMEM;
+
+ psci_reboot_mode_set_predefined_modes(reboot);
+ reboot->write = psci_reboot_mode_write;
+ reboot->dev = &fdev->dev;
+
+ ret = devm_reboot_mode_register(&fdev->dev, reboot);
+ if (ret) {
+ dev_err_probe(&fdev->dev, ret, "devm_reboot_mode_register failed %d\n", ret);
+ return ret;
+ }
+
+ return 0;
+}
+
+static int __init psci_reboot_mode_init(void)
+{
+ struct device_node *psci_np;
+ struct faux_device *fdev;
+ struct device_node *np;
+ int ret;
+
+ psci_np = of_find_compatible_node(NULL, NULL, "arm,psci-1.0");
+ if (!psci_np)
+ return -ENODEV;
+ /*
+ * Look for reboot-mode in the psci node. Even if the reboot-mode
+ * node is not defined in psci, continue to register with the
+ * reboot-mode driver and let the dev.ofnode be set as NULL.
+ */
+ np = of_find_node_by_name(psci_np, "reboot-mode");
+
+ fdev = faux_device_create("psci-reboot-mode", NULL, NULL);
Same comment as Bartosz (have you picked up his work and working towards
a solution) ?
thanks,
Shivendra