power: reset: Add a driver for the Microsemi Ocelot reset

The Microsemi Ocelot SoC has a register allowing to reset the MIPS core.
Unfortunately, the syscon-reboot driver can't be used directly (but almost)
as the reset control may be disabled using another register.

Cc: linux-pm@vger.kernel.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>

3 files changed, 96 insertions, 0 deletions

diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index a102e74ab24e..176bd6df1238 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -104,6 +104,13 @@ config POWER_RESET_MSM
         help
           Power off and restart support for Qualcomm boards.
 
+config POWER_RESET_OCELOT_RESET
+        bool "Microsemi Ocelot reset driver"
+        depends on MSCC_OCELOT || COMPILE_TEST
+        select MFD_SYSCON
+        help
+          This driver supports restart for Microsemi Ocelot SoC.
+
 config POWER_RESET_PIIX4_POWEROFF
         tristate "Intel PIIX4 power-off driver"
         depends on PCI
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index dcc92f5f7a37..6b9eb1393179 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
 obj-$(CONFIG_POWER_RESET_GPIO_RESTART) += gpio-restart.o
 obj-$(CONFIG_POWER_RESET_HISI) += hisi-reboot.o
 obj-$(CONFIG_POWER_RESET_MSM) += msm-poweroff.o
+obj-$(CONFIG_POWER_RESET_OCELOT_RESET) += ocelot-reset.o
 obj-$(CONFIG_POWER_RESET_PIIX4_POWEROFF) += piix4-poweroff.o
 obj-$(CONFIG_POWER_RESET_LTC2952) += ltc2952-poweroff.o
 obj-$(CONFIG_POWER_RESET_QNAP) += qnap-poweroff.o
diff --git a/drivers/power/reset/ocelot-reset.c b/drivers/power/reset/ocelot-reset.c
new file mode 100644
index 000000000000..5a13a5cc8188
--- /dev/null
+++ b/drivers/power/reset/ocelot-reset.c
@@ -0,0 +1,88 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Microsemi MIPS SoC reset driver
+ *
+ * License: Dual MIT/GPL
+ * Copyright (c) 2017 Microsemi Corporation
+ */
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/notifier.h>
+#include <linux/mfd/syscon.h>
+#include <linux/of_address.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+#include <linux/regmap.h>
+
+struct ocelot_reset_context {
+        void __iomem *base;
+        struct regmap *cpu_ctrl;
+        struct notifier_block restart_handler;
+};
+
+#define ICPU_CFG_CPU_SYSTEM_CTRL_RESET 0x20
+#define CORE_RST_PROTECT BIT(2)
+
+#define SOFT_CHIP_RST BIT(0)
+
+static int ocelot_restart_handle(struct notifier_block *this,
+                                 unsigned long mode, void *cmd)
+{
+        struct ocelot_reset_context *ctx = container_of(this, struct
+                                                        ocelot_reset_context,
+                                                        restart_handler);
+
+        /* Make sure the core is not protected from reset */
+        regmap_update_bits(ctx->cpu_ctrl, ICPU_CFG_CPU_SYSTEM_CTRL_RESET,
+                           CORE_RST_PROTECT, 0);
+
+        writel(SOFT_CHIP_RST, ctx->base);
+
+        pr_emerg("Unable to restart system\n");
+        return NOTIFY_DONE;
+}
+
+static int ocelot_reset_probe(struct platform_device *pdev)
+{
+        struct ocelot_reset_context *ctx;
+        struct resource *res;
+
+        struct device *dev = &pdev->dev;
+        int err;
+
+        ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
+        if (!ctx)
+                return -ENOMEM;
+
+        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+        ctx->base = devm_ioremap_resource(dev, res);
+        if (IS_ERR(ctx->base))
+                return PTR_ERR(ctx->base);
+
+        ctx->cpu_ctrl = syscon_regmap_lookup_by_compatible("mscc,ocelot-cpu-syscon");
+        if (IS_ERR(ctx->cpu_ctrl))
+                return PTR_ERR(ctx->cpu_ctrl);
+
+        ctx->restart_handler.notifier_call = ocelot_restart_handle;
+        ctx->restart_handler.priority = 192;
+        err = register_restart_handler(&ctx->restart_handler);
+        if (err)
+                dev_err(dev, "can't register restart notifier (err=%d)\n", err);
+
+        return err;
+}
+
+static const struct of_device_id ocelot_reset_of_match[] = {
+        { .compatible = "mscc,ocelot-chip-reset" },
+        {}
+};
+
+static struct platform_driver ocelot_reset_driver = {
+        .probe = ocelot_reset_probe,
+        .driver = {
+                .name = "ocelot-chip-reset",
+                .of_match_table = ocelot_reset_of_match,
+        },
+};
+builtin_platform_driver(ocelot_reset_driver);