--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Reset driver for the StarFive JH7100 SoC
+ *
+ * Copyright (C) 2021 Emil Renner Berthing <kernel@esmil.dk>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/mod_devicetable.h>
+#include <linux/platform_device.h>
+#include <linux/reset-controller.h>
+#include <linux/spinlock.h>
+
+#include <dt-bindings/reset/starfive-jh7100.h>
+
+/* register offsets */
+#define JH7100_RESET_ASSERT0 0x00
+#define JH7100_RESET_ASSERT1 0x04
+#define JH7100_RESET_ASSERT2 0x08
+#define JH7100_RESET_ASSERT3 0x0c
+#define JH7100_RESET_STATUS0 0x10
+#define JH7100_RESET_STATUS1 0x14
+#define JH7100_RESET_STATUS2 0x18
+#define JH7100_RESET_STATUS3 0x1c
+
+/*
+ * Writing a 1 to the n'th bit of the m'th ASSERT register asserts
+ * line 32m + n, and writing a 0 deasserts the same line.
+ * Most reset lines have their status inverted so a 0 bit in the STATUS
+ * register means the line is asserted and a 1 means it's deasserted. A few
+ * lines don't though, so store the expected value of the status registers when
+ * all lines are asserted.
+ */
+static const u64 jh7100_reset_asserted[2] = {
+ /* STATUS0 */
+ BIT_ULL_MASK(JH7100_RST_U74) |
+ BIT_ULL_MASK(JH7100_RST_VP6_DRESET) |
+ BIT_ULL_MASK(JH7100_RST_VP6_BRESET) |
+ /* STATUS1 */
+ BIT_ULL_MASK(JH7100_RST_HIFI4_DRESET) |
+ BIT_ULL_MASK(JH7100_RST_HIFI4_BRESET),
+ /* STATUS2 */
+ BIT_ULL_MASK(JH7100_RST_E24) |
+ /* STATUS3 */
+ 0,
+};
+
+struct jh7100_reset {
+ struct reset_controller_dev rcdev;
+ /* protect registers against concurrent read-modify-write */
+ spinlock_t lock;
+ void __iomem *base;
+};
+
+static inline struct jh7100_reset *
+jh7100_reset_from(struct reset_controller_dev *rcdev)
+{
+ return container_of(rcdev, struct jh7100_reset, rcdev);
+}
+
+static int jh7100_reset_update(struct reset_controller_dev *rcdev,
+ unsigned long id, bool assert)
+{
+ struct jh7100_reset *data = jh7100_reset_from(rcdev);
+ unsigned long offset = BIT_ULL_WORD(id);
+ u64 mask = BIT_ULL_MASK(id);
+ void __iomem *reg_assert = data->base + JH7100_RESET_ASSERT0 + offset * sizeof(u64);
+ void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + offset * sizeof(u64);
+ u64 done = jh7100_reset_asserted[offset] & mask;
+ u64 value;
+ unsigned long flags;
+ int ret;
+
+ if (!assert)
+ done ^= mask;
+
+ spin_lock_irqsave(&data->lock, flags);
+
+ value = readq(reg_assert);
+ if (assert)
+ value |= mask;
+ else
+ value &= ~mask;
+ writeq(value, reg_assert);
+
+ /* if the associated clock is gated, deasserting might otherwise hang forever */
+ ret = readq_poll_timeout_atomic(reg_status, value, (value & mask) == done, 0, 1000);
+
+ spin_unlock_irqrestore(&data->lock, flags);
+ return ret;
+}
+
+static int jh7100_reset_assert(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ return jh7100_reset_update(rcdev, id, true);
+}
+
+static int jh7100_reset_deassert(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ return jh7100_reset_update(rcdev, id, false);
+}
+
+static int jh7100_reset_reset(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ int ret;
+
+ ret = jh7100_reset_assert(rcdev, id);
+ if (ret)
+ return ret;
+
+ return jh7100_reset_deassert(rcdev, id);
+}
+
+static int jh7100_reset_status(struct reset_controller_dev *rcdev,
+ unsigned long id)
+{
+ struct jh7100_reset *data = jh7100_reset_from(rcdev);
+ unsigned long offset = BIT_ULL_WORD(id);
+ u64 mask = BIT_ULL_MASK(id);
+ void __iomem *reg_status = data->base + JH7100_RESET_STATUS0 + offset * sizeof(u64);
+ u64 value = readq(reg_status);
+
+ return !((value ^ jh7100_reset_asserted[offset]) & mask);
+}
+
+static const struct reset_control_ops jh7100_reset_ops = {
+ .assert = jh7100_reset_assert,
+ .deassert = jh7100_reset_deassert,
+ .reset = jh7100_reset_reset,
+ .status = jh7100_reset_status,
+};
+
+static int __init jh7100_reset_probe(struct platform_device *pdev)
+{
+ struct jh7100_reset *data;
+
+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->base = devm_platform_ioremap_resource(pdev, 0);
+ if (IS_ERR(data->base))
+ return PTR_ERR(data->base);
+
+ data->rcdev.ops = &jh7100_reset_ops;
+ data->rcdev.owner = THIS_MODULE;
+ data->rcdev.nr_resets = JH7100_RSTN_END;
+ data->rcdev.dev = &pdev->dev;
+ data->rcdev.of_node = pdev->dev.of_node;
+ spin_lock_init(&data->lock);
+
+ return devm_reset_controller_register(&pdev->dev, &data->rcdev);
+}
+
+static const struct of_device_id jh7100_reset_dt_ids[] = {
+ { .compatible = "starfive,jh7100-reset" },
+ { /* sentinel */ }
+};
+
+static struct platform_driver jh7100_reset_driver = {
+ .driver = {
+ .name = "jh7100-reset",
+ .of_match_table = jh7100_reset_dt_ids,
+ .suppress_bind_attrs = true,
+ },
+};
+builtin_platform_driver_probe(jh7100_reset_driver, jh7100_reset_probe);
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