[PATCH v4 08/42] power: reset: Add a driver for the ep93xx reset

[Nikita Shubin via B4 Relay <devnull+nikita.shubin.maquefel.me@kernel.org>]

From: Nikita Shubin <nikita.shubin@maquefel.me>

Implement the reset behaviour of the various EP93xx SoCS in drivers/power/reset.

It used to be located in arch/arm/mach-ep93xx.

Signed-off-by: Nikita Shubin <nikita.shubin@maquefel.me>
Acked-by: Sebastian Reichel <sre@kernel.org>
---
 drivers/power/reset/Kconfig          | 10 +++++
 drivers/power/reset/Makefile         |  1 +
 drivers/power/reset/ep93xx-restart.c | 85 ++++++++++++++++++++++++++++++++++++
 3 files changed, 96 insertions(+)

diff --git a/drivers/power/reset/Kconfig b/drivers/power/reset/Kconfig
index fff07b2bd77b..9c2aa9218841 100644
--- a/drivers/power/reset/Kconfig
+++ b/drivers/power/reset/Kconfig
@@ -75,6 +75,16 @@ config POWER_RESET_BRCMSTB
 	  Say Y here if you have a Broadcom STB board and you wish
 	  to have restart support.
 
+config POWER_RESET_EP93XX
+	bool "Cirrus EP93XX reset driver" if COMPILE_TEST
+	depends on MFD_SYSCON
+	default ARCH_EP93XX
+	help
+	  This driver provides restart support for Cirrus EP93XX SoC.
+
+	  Say Y here if you have a Cirrus EP93XX SoC and you wish
+	  to have restart support.
+
 config POWER_RESET_GEMINI_POWEROFF
 	bool "Cortina Gemini power-off driver"
 	depends on ARCH_GEMINI || COMPILE_TEST
diff --git a/drivers/power/reset/Makefile b/drivers/power/reset/Makefile
index d763e6735ee3..61f4e11619b2 100644
--- a/drivers/power/reset/Makefile
+++ b/drivers/power/reset/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_POWER_RESET_ATC260X) += atc260x-poweroff.o
 obj-$(CONFIG_POWER_RESET_AXXIA) += axxia-reset.o
 obj-$(CONFIG_POWER_RESET_BRCMKONA) += brcm-kona-reset.o
 obj-$(CONFIG_POWER_RESET_BRCMSTB) += brcmstb-reboot.o
+obj-$(CONFIG_POWER_RESET_EP93XX) += ep93xx-restart.o
 obj-$(CONFIG_POWER_RESET_GEMINI_POWEROFF) += gemini-poweroff.o
 obj-$(CONFIG_POWER_RESET_GPIO) += gpio-poweroff.o
 obj-$(CONFIG_POWER_RESET_GPIO_RESTART) += gpio-restart.o
diff --git a/drivers/power/reset/ep93xx-restart.c b/drivers/power/reset/ep93xx-restart.c
new file mode 100644
index 000000000000..4da456d45d29
--- /dev/null
+++ b/drivers/power/reset/ep93xx-restart.c
@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Cirrus EP93xx SoC reset driver
+ *
+ * Copyright (C) 2021 Nikita Shubin <nikita.shubin@maquefel.me>
+ */
+
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/mfd/syscon.h>
+#include <linux/notifier.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/reboot.h>
+
+#include <linux/soc/cirrus/ep93xx.h>
+
+#define EP93XX_SYSCON_DEVCFG		0x80
+#define EP93XX_SYSCON_DEVCFG_SWRST	BIT(31)
+
+struct ep93xx_restart {
+	struct regmap *map;
+	struct notifier_block restart_handler;
+};
+
+static int ep93xx_restart_handle(struct notifier_block *this,
+				 unsigned long mode, void *cmd)
+{
+	struct ep93xx_restart *priv =
+		container_of(this, struct ep93xx_restart, restart_handler);
+
+	/* Issue the reboot */
+	ep93xx_regmap_update_bits(priv->map, EP93XX_SYSCON_DEVCFG,
+				  EP93XX_SYSCON_DEVCFG_SWRST, EP93XX_SYSCON_DEVCFG_SWRST);
+	ep93xx_regmap_update_bits(priv->map, EP93XX_SYSCON_DEVCFG,
+				  EP93XX_SYSCON_DEVCFG_SWRST, 0);
+
+	return NOTIFY_DONE;
+}
+
+static int ep93xx_reboot_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct ep93xx_restart *priv;
+	struct device_node *parent;
+	int err;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	parent = of_get_parent(dev->of_node);
+	if (!parent)
+		return dev_err_probe(dev, -EINVAL, "no syscon parent for reboot node\n");
+
+	priv->map = syscon_node_to_regmap(parent);
+	of_node_put(parent);
+	if (IS_ERR(priv->map))
+		return dev_err_probe(dev, -EINVAL, "no syscon regmap\n");
+
+	priv->restart_handler.notifier_call = ep93xx_restart_handle;
+	priv->restart_handler.priority = 128;
+
+	err = register_restart_handler(&priv->restart_handler);
+	if (err)
+		return dev_err_probe(dev, err, "can't register restart notifier\n");
+
+	return 0;
+}
+
+static const struct of_device_id ep93xx_reboot_of_match[] = {
+	{
+		.compatible = "cirrus,ep9301-reboot",
+	},
+	{ /* sentinel */ }
+};
+
+static struct platform_driver ep93xx_reboot_driver = {
+	.probe = ep93xx_reboot_probe,
+	.driver = {
+		.name = "ep9301-reboot",
+		.of_match_table = ep93xx_reboot_of_match,
+	},
+};
+builtin_platform_driver(ep93xx_reboot_driver);

-- 
2.39.2