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Subject[PATCH 1/1] power: reset: nvmem-reboot-mode: use NVMEM as reboot mode write interface
Date
Add a new reboot mode write interface that is using a NVMEM cell,
called "reboot-mode", to store the reboot mode magic.

Signed-off-by: Nandor Han <nandor.han@vaisala.com>
---

Description
-----------
Extend the reboot mode driver to use a NVMEM cell as writing interface.

Testing
-------
The testing is done by configuring DT from a custom board.
The NVMEM cell is configured in an RTC non-volatile memory.

DT configurations:
`
...
reboot-mode-nvmem@0 {
compatible = "simple-mfd";
reboot-mode {
compatible = "nvmem-reboot-mode";
nvmem-cells = <&reboot_mode>;
nvmem-cell-names = "reboot-mode";

mode-test = <0x21969147>;
};
};
...
reboot_mode: nvmem_reboot_mode@0 {
reg = <0x00 0x4>;
};
...
`

1. Reboot the system using the command `reboot test`

2. Verify that kernel logs show that reboot was done in mode `test`:
PASS
`[ 413.957172] reboot: Restarting system with command 'test' `

3. Stop in U-Boot and verify that mode `test` magic value is present
in RTCs non-volatile memory: PASS

.../power/reset/nvmem-reboot-mode.txt | 32 ++++++++
drivers/power/reset/Kconfig | 9 +++
drivers/power/reset/Makefile | 1 +
drivers/power/reset/nvmem-reboot-mode.c | 75 +++++++++++++++++++
4 files changed, 117 insertions(+)
create mode 100644 Documentation/devicetree/bindings/power/reset/nvmem-reboot-mode.txt
create mode 100644 drivers/power/reset/nvmem-reboot-mode.c

diff --git a/Documentation/devicetree/bindings/power/reset/nvmem-reboot-mode.txt b/Documentation/devicetree/bindings/power/reset/nvmem-reboot-mode.txt
new file mode 100644
index 000000000000..2e1b86c31cb3
--- /dev/null
+++ b/Documentation/devicetree/bindings/power/reset/nvmem-reboot-mode.txt
@@ -0,0 +1,32 @@
+NVMEM reboot mode driver
+
+This driver gets reboot mode magic value from reboot-mode driver
+and stores it in a NVMEM cell named "reboot-mode". Then the bootloader
+can read it and take different action according to the magic
+value stored.
+
+This DT node should be represented as a sub-node of a "simple-mfd"
+node.
+
+Required properties:
+- compatible: should be "nvmem-reboot-mode".
+- nvmem-cells: A phandle to the reboot mode provided by a nvmem device.
+- nvmem-cell-names: Should be "reboot-mode".
+
+The rest of the properties should follow the generic reboot-mode description
+found in reboot-mode.txt
+
+Example:
+ reboot-mode-nvmem@0 {
+ compatible = "simple-mfd";
+ reboot-mode {
+ compatible = "nvmem-reboot-mode";
+ nvmem-cells = <&reboot_mode>;
+ nvmem-cell-names = "reboot-mode";
+
+ mode-normal = <0xAAAA5501>;
+ mode-bootloader = <0xBBBB5500>;
+ mode-recovery = <0xCCCC5502>;
+ mode-test = <0xDDDD5503>;
+ };
+ };
diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index 6533aa560aa1..bb4a4e854f96 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -245,5 +245,14 @@ config POWER_RESET_SC27XX
PMICs includes the SC2720, SC2721, SC2723, SC2730
and SC2731 chips.

+config NVMEM_REBOOT_MODE
+ tristate "Generic NVMEM reboot mode driver"
+ select REBOOT_MODE
+ help
+ Say y here will enable reboot mode driver. This will
+ get reboot mode arguments and store it in a NVMEM cell,
+ then the bootloader can read it and take different
+ action according to the mode.
+
endif

diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index 0aebee954ac1..85da3198e4e0 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -29,3 +29,4 @@ obj-$(CONFIG_POWER_RESET_ZX) += zx-reboot.o
obj-$(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
diff --git a/drivers/power/reset/nvmem-reboot-mode.c b/drivers/power/reset/nvmem-reboot-mode.c
new file mode 100644
index 000000000000..31b73c7a0dad
--- /dev/null
+++ b/drivers/power/reset/nvmem-reboot-mode.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) Vaisala Oyj. All rights reserved.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/nvmem-consumer.h>
+#include <linux/platform_device.h>
+#include <linux/reboot-mode.h>
+
+struct nvmem_reboot_mode {
+ struct reboot_mode_driver reboot;
+ struct nvmem_cell *cell;
+};
+
+static int nvmem_reboot_mode_write(struct reboot_mode_driver *reboot,
+ unsigned int magic)
+{
+ int ret;
+ struct nvmem_reboot_mode *nvmem_rbm;
+
+ nvmem_rbm = container_of(reboot, struct nvmem_reboot_mode, reboot);
+
+ ret = nvmem_cell_write(nvmem_rbm->cell, &magic, sizeof(magic));
+ if (ret < 0)
+ dev_err(reboot->dev, "update reboot mode bits failed\n");
+
+ return ret;
+}
+
+static int nvmem_reboot_mode_probe(struct platform_device *pdev)
+{
+ int ret;
+ struct nvmem_reboot_mode *nvmem_rbm;
+
+ nvmem_rbm = devm_kzalloc(&pdev->dev, sizeof(*nvmem_rbm), GFP_KERNEL);
+ if (!nvmem_rbm)
+ return -ENOMEM;
+
+ nvmem_rbm->reboot.dev = &pdev->dev;
+ nvmem_rbm->reboot.write = nvmem_reboot_mode_write;
+
+ nvmem_rbm->cell = devm_nvmem_cell_get(&pdev->dev, "reboot-mode");
+ if (IS_ERR(nvmem_rbm->cell)) {
+ dev_err(&pdev->dev, "failed to get the nvmem cell reboot-mode\n");
+ return PTR_ERR(nvmem_rbm->cell);
+ }
+
+ ret = devm_reboot_mode_register(&pdev->dev, &nvmem_rbm->reboot);
+ if (ret)
+ dev_err(&pdev->dev, "can't register reboot mode\n");
+
+ return ret;
+}
+
+static const struct of_device_id nvmem_reboot_mode_of_match[] = {
+ { .compatible = "nvmem-reboot-mode" },
+ {}
+};
+MODULE_DEVICE_TABLE(of, nvmem_reboot_mode_of_match);
+
+static struct platform_driver nvmem_reboot_mode_driver = {
+ .probe = nvmem_reboot_mode_probe,
+ .driver = {
+ .name = "nvmem-reboot-mode",
+ .of_match_table = nvmem_reboot_mode_of_match,
+ },
+};
+module_platform_driver(nvmem_reboot_mode_driver);
+
+MODULE_AUTHOR("Nandor Han <nandor.han@vaisala.com>");
+MODULE_DESCRIPTION("NVMEM reboot mode driver");
+MODULE_LICENSE("GPL v2");
--
2.17.2
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