power: reset: nvmem-reboot-mode: use NVMEM as reboot mode write interface

Add a new reboot mode write interface that is using an NVMEM cell
to store the reboot mode magic.

Signed-off-by: Nandor Han <nandor.han@vaisala.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

3 files changed, 86 insertions, 0 deletions

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..e229308d43e2
--- /dev/null
+++ b/drivers/power/reset/nvmem-reboot-mode.c
@@ -0,0 +1,76 @@
+// 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/of.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");