soc: apple: Add driver for Apple PMGR power state controls

Implements genpd and reset providers for downstream devices. Each
instance of the driver binds to a single register and represents a
single SoC power domain.

The driver does not currently implement all features (clockgate-only
state, misc flags), but we declare the respective registers for
documentation purposes. These features will be added as they become
useful for downstream devices.

This also creates the apple/soc tree and Kconfig submenu.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Hector Martin <marcan@marcan.st>

drivers/soc/Kconfig

@@ -3,6 +3,7 @@ menu "SOC (System On Chip) specific Drivers"
 
 source "drivers/soc/actions/Kconfig"
 source "drivers/soc/amlogic/Kconfig"
+source "drivers/soc/apple/Kconfig"
 source "drivers/soc/aspeed/Kconfig"
 source "drivers/soc/atmel/Kconfig"
 source "drivers/soc/bcm/Kconfig"

drivers/soc/Makefile

@@ -4,6 +4,7 @@
 #
 
 obj-$(CONFIG_ARCH_ACTIONS)	+= actions/
+obj-$(CONFIG_ARCH_APPLE)	+= apple/
 obj-y				+= aspeed/
 obj-$(CONFIG_ARCH_AT91)		+= atmel/
 obj-y				+= bcm/

drivers/soc/apple/Kconfig

+# SPDX-License-Identifier: GPL-2.0-only
+
+if ARCH_APPLE || COMPILE_TEST
+
+menu "Apple SoC drivers"
+
+config APPLE_PMGR_PWRSTATE
+	tristate "Apple SoC PMGR power state control"
+	depends on PM
+	select REGMAP
+	select MFD_SYSCON
+	select PM_GENERIC_DOMAINS
+	select RESET_CONTROLLER
+	default ARCH_APPLE
+	help
+	  The PMGR block in Apple SoCs provides high-level power state
+	  controls for SoC devices. This driver manages them through the
+	  generic power domain framework, and also provides reset support.
+
+endmenu
+
+endif

drivers/soc/apple/Makefile

+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_APPLE_PMGR_PWRSTATE)	+= apple-pmgr-pwrstate.o

drivers/soc/apple/apple-pmgr-pwrstate.c

+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+/*
+ * Apple SoC PMGR device power state driver
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/bitops.h>
+#include <linux/bitfield.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+#include <linux/reset-controller.h>
+#include <linux/module.h>
+
+#define APPLE_PMGR_RESET        BIT(31)
+#define APPLE_PMGR_AUTO_ENABLE  BIT(28)
+#define APPLE_PMGR_PS_AUTO      GENMASK(27, 24)
+#define APPLE_PMGR_PARENT_OFF   BIT(11)
+#define APPLE_PMGR_DEV_DISABLE  BIT(10)
+#define APPLE_PMGR_WAS_CLKGATED BIT(9)
+#define APPLE_PMGR_WAS_PWRGATED BIT(8)
+#define APPLE_PMGR_PS_ACTUAL    GENMASK(7, 4)
+#define APPLE_PMGR_PS_TARGET    GENMASK(3, 0)
+
+#define APPLE_PMGR_FLAGS        (APPLE_PMGR_WAS_CLKGATED | APPLE_PMGR_WAS_PWRGATED)
+
+#define APPLE_PMGR_PS_ACTIVE    0xf
+#define APPLE_PMGR_PS_CLKGATE   0x4
+#define APPLE_PMGR_PS_PWRGATE   0x0
+
+#define APPLE_PMGR_PS_SET_TIMEOUT 100
+#define APPLE_PMGR_RESET_TIME 1
+
+struct apple_pmgr_ps {
+	struct device *dev;
+	struct generic_pm_domain genpd;
+	struct reset_controller_dev rcdev;
+	struct regmap *regmap;
+	u32 offset;
+};
+
+#define genpd_to_apple_pmgr_ps(_genpd) container_of(_genpd, struct apple_pmgr_ps, genpd)
+#define rcdev_to_apple_pmgr_ps(_rcdev) container_of(_rcdev, struct apple_pmgr_ps, rcdev)
+
+static int apple_pmgr_ps_set(struct generic_pm_domain *genpd, u32 pstate, bool auto_enable)
+{
+	int ret;
+	struct apple_pmgr_ps *ps = genpd_to_apple_pmgr_ps(genpd);
+	u32 reg;
+
+	ret = regmap_read(ps->regmap, ps->offset, &reg);
+	if (ret < 0)
+		return ret;
+
+	/* Resets are synchronous, and only work if the device is powered and clocked. */
+	if (reg & APPLE_PMGR_RESET && pstate != APPLE_PMGR_PS_ACTIVE)
+		dev_err(ps->dev, "PS %s: powering off with RESET active\n",
+			genpd->name);
+
+	reg &= ~(APPLE_PMGR_AUTO_ENABLE | APPLE_PMGR_FLAGS | APPLE_PMGR_PS_TARGET);
+	reg |= FIELD_PREP(APPLE_PMGR_PS_TARGET, pstate);
+
+	dev_dbg(ps->dev, "PS %s: pwrstate = 0x%x: 0x%x\n", genpd->name, pstate, reg);
+
+	regmap_write(ps->regmap, ps->offset, reg);
+
+	ret = regmap_read_poll_timeout_atomic(
+		ps->regmap, ps->offset, reg,
+		(FIELD_GET(APPLE_PMGR_PS_ACTUAL, reg) == pstate), 1,
+		APPLE_PMGR_PS_SET_TIMEOUT);
+	if (ret < 0)
+		dev_err(ps->dev, "PS %s: Failed to reach power state 0x%x (now: 0x%x)\n",
+			genpd->name, pstate, reg);
+
+	if (auto_enable) {
+		/* Not all devices implement this; this is a no-op where not implemented. */
+		reg &= ~APPLE_PMGR_FLAGS;
+		reg |= APPLE_PMGR_AUTO_ENABLE;
+		regmap_write(ps->regmap, ps->offset, reg);
+	}
+
+	return ret;
+}
+
+static bool apple_pmgr_ps_is_active(struct apple_pmgr_ps *ps)
+{
+	u32 reg = 0;
+
+	regmap_read(ps->regmap, ps->offset, &reg);
+	/*
+	 * We consider domains as active if they are actually on, or if they have auto-PM
+	 * enabled and the intended target is on.
+	 */
+	return (FIELD_GET(APPLE_PMGR_PS_ACTUAL, reg) == APPLE_PMGR_PS_ACTIVE ||
+		(FIELD_GET(APPLE_PMGR_PS_TARGET, reg) == APPLE_PMGR_PS_ACTIVE &&
+		 reg & APPLE_PMGR_AUTO_ENABLE));
+}
+
+static int apple_pmgr_ps_power_on(struct generic_pm_domain *genpd)
+{
+	return apple_pmgr_ps_set(genpd, APPLE_PMGR_PS_ACTIVE, true);
+}
+
+static int apple_pmgr_ps_power_off(struct generic_pm_domain *genpd)
+{
+	return apple_pmgr_ps_set(genpd, APPLE_PMGR_PS_PWRGATE, false);
+}
+
+static int apple_pmgr_reset_assert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct apple_pmgr_ps *ps = rcdev_to_apple_pmgr_ps(rcdev);
+
+	mutex_lock(&ps->genpd.mlock);
+
+	if (ps->genpd.status == GENPD_STATE_OFF)
+		dev_err(ps->dev, "PS 0x%x: asserting RESET while powered down\n", ps->offset);
+
+	dev_dbg(ps->dev, "PS 0x%x: assert reset\n", ps->offset);
+	/* Quiesce device before asserting reset */
+	regmap_update_bits(ps->regmap, ps->offset, APPLE_PMGR_FLAGS | APPLE_PMGR_DEV_DISABLE,
+			   APPLE_PMGR_DEV_DISABLE);
+	regmap_update_bits(ps->regmap, ps->offset, APPLE_PMGR_FLAGS | APPLE_PMGR_RESET,
+			   APPLE_PMGR_RESET);
+
+	mutex_unlock(&ps->genpd.mlock);
+
+	return 0;
+}
+
+static int apple_pmgr_reset_deassert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct apple_pmgr_ps *ps = rcdev_to_apple_pmgr_ps(rcdev);
+
+	mutex_lock(&ps->genpd.mlock);
+
+	dev_dbg(ps->dev, "PS 0x%x: deassert reset\n", ps->offset);
+	regmap_update_bits(ps->regmap, ps->offset, APPLE_PMGR_FLAGS | APPLE_PMGR_RESET, 0);
+	regmap_update_bits(ps->regmap, ps->offset, APPLE_PMGR_FLAGS | APPLE_PMGR_DEV_DISABLE, 0);
+
+	if (ps->genpd.status == GENPD_STATE_OFF)
+		dev_err(ps->dev, "PS 0x%x: RESET was deasserted while powered down\n", ps->offset);
+
+	mutex_unlock(&ps->genpd.mlock);
+
+	return 0;
+}
+
+static int apple_pmgr_reset_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	int ret;
+
+	ret = apple_pmgr_reset_assert(rcdev, id);
+	if (ret)
+		return ret;
+
+	usleep_range(APPLE_PMGR_RESET_TIME, 2 * APPLE_PMGR_RESET_TIME);
+
+	return apple_pmgr_reset_deassert(rcdev, id);
+}
+
+static int apple_pmgr_reset_status(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct apple_pmgr_ps *ps = rcdev_to_apple_pmgr_ps(rcdev);
+	u32 reg = 0;
+
+	regmap_read(ps->regmap, ps->offset, &reg);
+
+	return !!(reg & APPLE_PMGR_RESET);
+}
+
+const struct reset_control_ops apple_pmgr_reset_ops = {
+	.assert		= apple_pmgr_reset_assert,
+	.deassert	= apple_pmgr_reset_deassert,
+	.reset		= apple_pmgr_reset_reset,
+	.status		= apple_pmgr_reset_status,
+};
+
+static int apple_pmgr_reset_xlate(struct reset_controller_dev *rcdev,
+				  const struct of_phandle_args *reset_spec)
+{
+	return 0;
+}
+
+static int apple_pmgr_ps_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
+	struct apple_pmgr_ps *ps;
+	struct regmap *regmap;
+	struct of_phandle_iterator it;
+	int ret;
+	const char *name;
+	bool active;
+
+	regmap = syscon_node_to_regmap(node->parent);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	ps = devm_kzalloc(dev, sizeof(*ps), GFP_KERNEL);
+	if (!ps)
+		return -ENOMEM;
+
+	ps->dev = dev;
+	ps->regmap = regmap;
+
+	ret = of_property_read_string(node, "label", &name);
+	if (ret < 0) {
+		dev_err(dev, "missing label property\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(node, "reg", &ps->offset);
+	if (ret < 0) {
+		dev_err(dev, "missing reg property\n");
+		return ret;
+	}
+
+	ps->genpd.name = name;
+	ps->genpd.power_on = apple_pmgr_ps_power_on;
+	ps->genpd.power_off = apple_pmgr_ps_power_off;
+
+	active = apple_pmgr_ps_is_active(ps);
+	if (of_property_read_bool(node, "apple,always-on")) {
+		ps->genpd.flags |= GENPD_FLAG_ALWAYS_ON;
+		if (!active) {
+			dev_warn(dev, "always-on domain %s is not on at boot\n", name);
+			/* Turn it on so pm_genpd_init does not fail */
+			active = apple_pmgr_ps_power_on(&ps->genpd) == 0;
+		}
+	}
+
+	/* Turn on auto-PM if the domain is already on */
+	if (active)
+		regmap_update_bits(regmap, ps->offset, APPLE_PMGR_FLAGS | APPLE_PMGR_AUTO_ENABLE,
+				   APPLE_PMGR_AUTO_ENABLE);
+
+	ret = pm_genpd_init(&ps->genpd, NULL, !active);
+	if (ret < 0) {
+		dev_err(dev, "pm_genpd_init failed\n");
+		return ret;
+	}
+
+	ret = of_genpd_add_provider_simple(node, &ps->genpd);
+	if (ret < 0) {
+		dev_err(dev, "of_genpd_add_provider_simple failed\n");
+		return ret;
+	}
+
+	of_for_each_phandle(&it, ret, node, "power-domains", "#power-domain-cells", -1) {
+		struct of_phandle_args parent, child;
+
+		parent.np = it.node;
+		parent.args_count = of_phandle_iterator_args(&it, parent.args, MAX_PHANDLE_ARGS);
+		child.np = node;
+		child.args_count = 0;
+		ret = of_genpd_add_subdomain(&parent, &child);
+
+		if (ret == -EPROBE_DEFER) {
+			of_node_put(parent.np);
+			goto err_remove;
+		} else if (ret < 0) {
+			dev_err(dev, "failed to add to parent domain: %d (%s -> %s)\n",
+				ret, it.node->name, node->name);
+			of_node_put(parent.np);
+			goto err_remove;
+		}
+	}
+
+	/*
+	 * Do not participate in regular PM; parent power domains are handled via the
+	 * genpd hierarchy.
+	 */
+	pm_genpd_remove_device(dev);
+
+	ps->rcdev.owner = THIS_MODULE;
+	ps->rcdev.nr_resets = 1;
+	ps->rcdev.ops = &apple_pmgr_reset_ops;
+	ps->rcdev.of_node = dev->of_node;
+	ps->rcdev.of_reset_n_cells = 0;
+	ps->rcdev.of_xlate = apple_pmgr_reset_xlate;
+
+	ret = devm_reset_controller_register(dev, &ps->rcdev);
+	if (ret < 0)
+		goto err_remove;
+
+	return 0;
+err_remove:
+	of_genpd_del_provider(node);
+	pm_genpd_remove(&ps->genpd);
+	return ret;
+}
+
+static const struct of_device_id apple_pmgr_ps_of_match[] = {
+	{ .compatible = "apple,pmgr-pwrstate" },
+	{}
+};
+
+MODULE_DEVICE_TABLE(of, apple_pmgr_ps_of_match);
+
+static struct platform_driver apple_pmgr_ps_driver = {
+	.probe = apple_pmgr_ps_probe,
+	.driver = {
+		.name = "apple-pmgr-pwrstate",
+		.of_match_table = apple_pmgr_ps_of_match,
+	},
+};
+
+MODULE_AUTHOR("Hector Martin <marcan@marcan.st>");
+MODULE_DESCRIPTION("PMGR power state driver for Apple SoCs");
+MODULE_LICENSE("GPL v2");
+
+module_platform_driver(apple_pmgr_ps_driver);