[PATCH 2/4] reset: eyeq5: add driver

[Théo Lebrun]

Add the Mobileye EyeQ5 reset controller driver. See the header comment
for more information on how it works. This driver is specific to this
platform; it might grow to add later support of other platforms from
Mobileye.

Signed-off-by: Théo Lebrun <theo.lebrun@xxxxxxxxxxx>
---
 MAINTAINERS                 |   1 +
 drivers/reset/Kconfig       |  13 ++
 drivers/reset/Makefile      |   1 +
 drivers/reset/reset-eyeq5.c | 323 ++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 338 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 9096a940b425..138e0303c5da 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -14557,6 +14557,7 @@ F:	Documentation/devicetree/bindings/reset/mobileye,eyeq5-reset.yaml
 F:	arch/mips/boot/dts/mobileye/
 F:	arch/mips/configs/generic/board-eyeq5.config
 F:	arch/mips/generic/board-epm5.its.S
+F:	drivers/reset/reset-eyeq5.c
 F:	include/dt-bindings/reset/mobileye,eyeq5-reset.h
 F:	include/dt-bindings/soc/mobileye,eyeq5.h
 
diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index ccd59ddd7610..488f2f38a2e2 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -66,6 +66,19 @@ config RESET_BRCMSTB_RESCAL
 	  This enables the RESCAL reset controller for SATA, PCIe0, or PCIe1 on
 	  BCM7216.
 
+config RESET_EYEQ5
+	bool "Mobileye EyeQ5 reset controller"
+	depends on MFD_SYSCON
+	depends on SOC_EYEQ5 || COMPILE_TEST
+	default SOC_EYEQ5
+	help
+	  This enables the Mobileye EyeQ5 reset controller; a custom IP block
+	  for this platform.
+
+	  It has three domains, with a varying number of resets in each of them.
+	  Registers are located in a shared register region called OLB accessed
+	  through a syscon & regmap.
+
 config RESET_HSDK
 	bool "Synopsys HSDK Reset Driver"
 	depends on HAS_IOMEM
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 8270da8a4baa..4fabe0070390 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -11,6 +11,7 @@ obj-$(CONFIG_RESET_BCM6345) += reset-bcm6345.o
 obj-$(CONFIG_RESET_BERLIN) += reset-berlin.o
 obj-$(CONFIG_RESET_BRCMSTB) += reset-brcmstb.o
 obj-$(CONFIG_RESET_BRCMSTB_RESCAL) += reset-brcmstb-rescal.o
+obj-$(CONFIG_RESET_EYEQ5) += reset-eyeq5.o
 obj-$(CONFIG_RESET_HSDK) += reset-hsdk.o
 obj-$(CONFIG_RESET_IMX7) += reset-imx7.o
 obj-$(CONFIG_RESET_INTEL_GW) += reset-intel-gw.o
diff --git a/drivers/reset/reset-eyeq5.c b/drivers/reset/reset-eyeq5.c
new file mode 100644
index 000000000000..45bb330f35ed
--- /dev/null
+++ b/drivers/reset/reset-eyeq5.c
@@ -0,0 +1,323 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Reset driver for the Mobileye EyeQ5 platform.
+ *
+ * The registers are located in a syscon region called OLB. We handle three
+ * reset domains. Domains 0 and 2 look similar in that they both use one bit
+ * per reset line. Domain 1 has a register per reset.
+ *
+ * We busy-wait after updating a reset in domains 0 or 1. The reason is hardware
+ * logic built-in self-test (LBIST) that might be enabled.
+ *
+ * We use eq5r_ as prefix, as-in "EyeQ5 Reset", but way shorter.
+ *
+ * Copyright (C) 2023 Mobileye Vision Technologies Ltd.
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+#include <linux/mutex.h>
+
+/* Offsets into the OLB region as well as masks for domain 1 registers. */
+#define EQ5R_OLB_SARCR0			(0x004)
+#define EQ5R_OLB_SARCR1			(0x008)
+#define EQ5R_OLB_PCIE_GP		(0x120)
+#define EQ5R_OLB_ACRP_REG(n)		(0x200 + 4 * (n)) // n=0..12
+#define EQ5R_OLB_ACRP_PD_REQ		BIT(0)
+#define EQ5R_OLB_ACRP_ST_POWER_DOWN	BIT(27)
+#define EQ5R_OLB_ACRP_ST_ACTIVE		BIT(29)
+
+/* Vendor-provided values. D1 has a long timeout because of LBIST. */
+#define D0_TIMEOUT_POLL			10
+#define D1_TIMEOUT_POLL			40000
+
+/* Masks for valid reset lines in each domain. This array is also used to get
+ * the domain and reset counts.
+ */
+static const u32 eq5r_valid_masks[] = { 0x0FFFFFF8, 0x00001FFF, 0x0007BFFF };
+
+#define EQ5R_DOMAIN_COUNT ARRAY_SIZE(eq5r_valid_masks)
+
+struct eq5r_private {
+	struct mutex mutexes[EQ5R_DOMAIN_COUNT]; /* We serialize all reset operations. */
+	struct regmap *olb;			 /* Writes go to a syscon regmap. */
+	struct reset_controller_dev rcdev;
+};
+
+static int _eq5r_busy_wait(struct eq5r_private *priv, struct device *dev,
+			   u32 domain, u32 offset, bool assert)
+{
+	unsigned int val, mask;
+	int i;
+
+	lockdep_assert_held(&priv->mutexes[domain]);
+
+	switch (domain) {
+	case 0:
+		for (i = 0; i < D0_TIMEOUT_POLL; i++) {
+			regmap_read(priv->olb, EQ5R_OLB_SARCR1, &val);
+			val = !(val & BIT(offset));
+			if (val == assert)
+				return 0;
+			__udelay(1);
+		}
+		break;
+	case 1:
+		mask = assert ? EQ5R_OLB_ACRP_ST_POWER_DOWN : EQ5R_OLB_ACRP_ST_ACTIVE;
+		for (i = 0; i < D1_TIMEOUT_POLL; i++) {
+			regmap_read(priv->olb, EQ5R_OLB_ACRP_REG(offset), &val);
+			if (val & mask)
+				return 0;
+			__udelay(1);
+		}
+		break;
+	case 2:
+		return 0; /* No busy waiting for domain 2. */
+	default:
+		WARN_ON(1);
+		return -EINVAL;
+	}
+
+	dev_dbg(dev, "%u-%u: timeout\n", domain, offset);
+	return -ETIMEDOUT;
+}
+
+static void _eq5r_assert(struct eq5r_private *priv, u32 domain, u32 offset)
+{
+	lockdep_assert_held(&priv->mutexes[domain]);
+
+	switch (domain) {
+	case 0:
+		regmap_clear_bits(priv->olb, EQ5R_OLB_SARCR0, BIT(offset));
+		break;
+	case 1:
+		regmap_set_bits(priv->olb, EQ5R_OLB_ACRP_REG(offset),
+				EQ5R_OLB_ACRP_PD_REQ);
+		break;
+	case 2:
+		regmap_clear_bits(priv->olb, EQ5R_OLB_PCIE_GP, BIT(offset));
+		break;
+	default:
+		WARN_ON(1);
+	}
+}
+
+static int eq5r_assert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct eq5r_private *priv = dev_get_drvdata(rcdev->dev);
+	u32 offset = id & GENMASK(7, 0);
+	u32 domain = id >> 8;
+	int ret;
+
+	if (WARN_ON(domain >= EQ5R_DOMAIN_COUNT))
+		return -EINVAL;
+
+	dev_dbg(rcdev->dev, "%u-%u: assert request\n", domain, offset);
+
+	mutex_lock(&priv->mutexes[domain]);
+	_eq5r_assert(priv, domain, offset);
+	ret = _eq5r_busy_wait(priv, rcdev->dev, domain, offset, true);
+	mutex_unlock(&priv->mutexes[domain]);
+
+	return ret;
+}
+
+static void _eq5r_deassert(struct eq5r_private *priv, u32 domain, u32 offset)
+{
+	lockdep_assert_held(&priv->mutexes[domain]);
+
+	switch (domain) {
+	case 0:
+		regmap_set_bits(priv->olb, EQ5R_OLB_SARCR0, BIT(offset));
+		break;
+	case 1:
+		regmap_clear_bits(priv->olb, EQ5R_OLB_ACRP_REG(offset),
+				  EQ5R_OLB_ACRP_PD_REQ);
+		break;
+	case 2:
+		regmap_set_bits(priv->olb, EQ5R_OLB_PCIE_GP, BIT(offset));
+		break;
+	default:
+		WARN_ON(1);
+	}
+}
+
+static int eq5r_deassert(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct eq5r_private *priv = dev_get_drvdata(rcdev->dev);
+	u32 offset = id & GENMASK(7, 0);
+	u32 domain = id >> 8;
+	int ret;
+
+	if (WARN_ON(domain >= EQ5R_DOMAIN_COUNT))
+		return -EINVAL;
+
+	dev_dbg(rcdev->dev, "%u-%u: deassert request\n", domain, offset);
+
+	mutex_lock(&priv->mutexes[domain]);
+	_eq5r_deassert(priv, domain, offset);
+	ret = _eq5r_busy_wait(priv, rcdev->dev, domain, offset, false);
+	mutex_unlock(&priv->mutexes[domain]);
+
+	return ret;
+}
+
+static int eq5r_reset(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct device *dev = rcdev->dev;
+	struct eq5r_private *priv = dev_get_drvdata(dev);
+	u32 offset = id & GENMASK(7, 0);
+	u32 domain = id >> 8;
+	int ret;
+
+	if (WARN_ON(domain >= EQ5R_DOMAIN_COUNT))
+		return -EINVAL;
+
+	dev_dbg(dev, "%u-%u: reset request\n", domain, offset);
+
+	mutex_lock(&priv->mutexes[domain]);
+
+	_eq5r_assert(priv, domain, offset);
+	ret = _eq5r_busy_wait(priv, dev, domain, offset, true);
+	if (ret) /* don't let an error disappear silently */
+		dev_warn(dev, "%u-%u: reset assert failed: %d\n",
+			 domain, offset, ret);
+
+	_eq5r_deassert(priv, domain, offset);
+	ret = _eq5r_busy_wait(priv, dev, domain, offset, false);
+
+	mutex_unlock(&priv->mutexes[domain]);
+
+	return ret;
+}
+
+static int eq5r_status(struct reset_controller_dev *rcdev, unsigned long id)
+{
+	struct eq5r_private *priv = dev_get_drvdata(rcdev->dev);
+	u32 offset = id & GENMASK(7, 0);
+	u32 domain = id >> 8;
+	unsigned int val;
+	int ret;
+
+	if (WARN_ON(domain >= EQ5R_DOMAIN_COUNT))
+		return -EINVAL;
+
+	dev_dbg(rcdev->dev, "%u-%u: status request\n", domain, offset);
+
+	mutex_lock(&priv->mutexes[domain]);
+
+	switch (domain) {
+	case 0:
+		regmap_read(priv->olb, EQ5R_OLB_SARCR1, &val);
+		ret = !(val & BIT(offset));
+		break;
+	case 1:
+		regmap_read(priv->olb, EQ5R_OLB_ACRP_REG(offset), &val);
+		ret = !(val & EQ5R_OLB_ACRP_ST_ACTIVE);
+		break;
+	case 2:
+		regmap_read(priv->olb, EQ5R_OLB_PCIE_GP, &val);
+		ret = !(val & BIT(offset));
+		break;
+	}
+
+	mutex_unlock(&priv->mutexes[domain]);
+
+	return ret;
+}
+
+static const struct reset_control_ops eq5r_ops = {
+	.reset	  = eq5r_reset,
+	.assert	  = eq5r_assert,
+	.deassert = eq5r_deassert,
+	.status	  = eq5r_status,
+};
+
+static int eq5r_of_xlate(struct reset_controller_dev *rcdev,
+			 const struct of_phandle_args *reset_spec)
+{
+	u32 domain, offset;
+
+	if (WARN_ON(reset_spec->args_count != 2))
+		return -EINVAL;
+
+	domain = reset_spec->args[0];
+	offset = reset_spec->args[1];
+
+	if (domain >= EQ5R_DOMAIN_COUNT || offset > 31 ||
+	    !(eq5r_valid_masks[domain] & BIT(offset))) {
+		dev_err(rcdev->dev, "%u-%u: invalid reset\n", domain, offset);
+		return -EINVAL;
+	}
+
+	return (domain << 8) | offset;
+}
+
+static int eq5r_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct device_node *parent_np = of_get_parent(np);
+	struct eq5r_private *priv;
+	int ret, i;
+
+	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, priv);
+
+	priv->olb = ERR_PTR(-ENODEV);
+	if (parent_np)
+		priv->olb = syscon_node_to_regmap(parent_np);
+	if (IS_ERR(priv->olb))
+		priv->olb = syscon_regmap_lookup_by_phandle(np, "mobileye,olb");
+	if (IS_ERR(priv->olb))
+		return PTR_ERR(priv->olb);
+
+	for (i = 0; i < EQ5R_DOMAIN_COUNT; i++)
+		mutex_init(&priv->mutexes[i]);
+
+	priv->rcdev.ops = &eq5r_ops;
+	priv->rcdev.owner = THIS_MODULE;
+	priv->rcdev.dev = dev;
+	priv->rcdev.of_node = np;
+	priv->rcdev.of_reset_n_cells = 2;
+	priv->rcdev.of_xlate = eq5r_of_xlate;
+
+	priv->rcdev.nr_resets = 0;
+	for (i = 0; i < EQ5R_DOMAIN_COUNT; i++)
+		priv->rcdev.nr_resets += __builtin_popcount(eq5r_valid_masks[i]);
+
+	ret = reset_controller_register(&priv->rcdev);
+	if (ret) {
+		dev_err(dev, "Failed registering reset controller: %d\n", ret);
+		return ret;
+	}
+
+	dev_info(dev, "probed\n");
+
+	return 0;
+}
+
+static const struct of_device_id eq5r_match_table[] = {
+	{ .compatible = "mobileye,eyeq5-reset" },
+	{}
+};
+
+static struct platform_driver eq5r_driver = {
+	.probe = eq5r_probe,
+	.driver = {
+		.name = "eyeq5-reset",
+		.of_match_table = eq5r_match_table,
+	},
+};
+
+static int __init eq5r_init(void)
+{
+	return platform_driver_register(&eq5r_driver);
+}
+
+arch_initcall(eq5r_init);

-- 
2.43.0