--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+//
+// Register cache access API - maple tree based cache
+//
+// Copyright 2023 Arm, Ltd
+//
+// Author: Mark Brown <broonie@kernel.org>
+
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/maple_tree.h>
+#include <linux/slab.h>
+
+#include "internal.h"
+
+static int regcache_maple_read(struct regmap *map,
+ unsigned int reg, unsigned int *value)
+{
+ struct maple_tree *mt = map->cache;
+ MA_STATE(mas, mt, reg, reg);
+ unsigned long *entry;
+
+ rcu_read_lock();
+
+ entry = mas_find(&mas, reg);
+ if (!entry) {
+ rcu_read_unlock();
+ return -ENOENT;
+ }
+
+ *value = entry[reg - mas.index];
+
+ rcu_read_unlock();
+
+ return 0;
+}
+
+static int regcache_maple_write(struct regmap *map, unsigned int reg,
+ unsigned int val)
+{
+ struct maple_tree *mt = map->cache;
+ MA_STATE(mas, mt, reg, reg);
+ unsigned long *entry, *upper, *lower;
+ unsigned long index, last;
+ size_t lower_sz, upper_sz;
+ int ret;
+
+ rcu_read_lock();
+
+ entry = mas_find(&mas, reg);
+ if (entry) {
+ entry[reg - mas.index] = val;
+ rcu_read_unlock();
+ return 0;
+ }
+
+ /* Any adjacent entries to extend/merge? */
+ mas_set_range(&mas, reg - 1, reg + 1);
+ index = reg;
+ last = reg;
+
+ lower = mas_find(&mas, reg - 1);
+ if (lower) {
+ index = mas.index;
+ lower_sz = (mas.last - mas.index + 1) * sizeof(unsigned long);
+ }
+
+ upper = mas_find(&mas, reg + 1);
+ if (upper) {
+ last = mas.last;
+ upper_sz = (mas.last - mas.index + 1) * sizeof(unsigned long);
+ }
+
+ rcu_read_unlock();
+
+ entry = kmalloc((last - index + 1) * sizeof(unsigned long),
+ GFP_KERNEL);
+ if (!entry)
+ return -ENOMEM;
+
+ if (lower)
+ memcpy(entry, lower, lower_sz);
+ entry[reg - index] = val;
+ if (upper)
+ memcpy(&entry[reg - index + 1], upper, upper_sz);
+
+ /*
+ * This is safe because the regmap lock means the Maple lock
+ * is redundant, but we need to take it due to lockdep asserts
+ * in the maple tree code.
+ */
+ mas_lock(&mas);
+
+ mas_set_range(&mas, index, last);
+ ret = mas_store_gfp(&mas, entry, GFP_KERNEL);
+
+ mas_unlock(&mas);
+
+ if (ret == 0) {
+ kfree(lower);
+ kfree(upper);
+ }
+
+ return ret;
+}
+
+static int regcache_maple_drop(struct regmap *map, unsigned int min,
+ unsigned int max)
+{
+ struct maple_tree *mt = map->cache;
+ MA_STATE(mas, mt, min, max);
+ unsigned long *entry, *lower, *upper;
+ unsigned long lower_index, lower_last;
+ unsigned long upper_index, upper_last;
+ int ret;
+
+ lower = NULL;
+ upper = NULL;
+
+ mas_lock(&mas);
+
+ mas_for_each(&mas, entry, max) {
+ /*
+ * This is safe because the regmap lock means the
+ * Maple lock is redundant, but we need to take it due
+ * to lockdep asserts in the maple tree code.
+ */
+ mas_unlock(&mas);
+
+ /* Do we need to save any of this entry? */
+ if (mas.index < min) {
+ lower_index = mas.index;
+ lower_last = min -1;
+
+ lower = kmemdup(entry, ((min - mas.index) *
+ sizeof(unsigned long)),
+ GFP_KERNEL);
+ if (!lower) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
+
+ if (mas.last > max) {
+ upper_index = max + 1;
+ upper_last = mas.last;
+
+ upper = kmemdup(&entry[max + 1],
+ ((mas.last - max) *
+ sizeof(unsigned long)),
+ GFP_KERNEL);
+ if (!upper) {
+ ret = -ENOMEM;
+ goto out;
+ }
+ }
+
+ kfree(entry);
+ mas_lock(&mas);
+ mas_erase(&mas);
+
+ /* Insert new nodes with the saved data */
+ if (lower) {
+ mas_set_range(&mas, lower_index, lower_last);
+ ret = mas_store_gfp(&mas, lower, GFP_KERNEL);
+ if (ret != 0)
+ goto out;
+ lower = NULL;
+ }
+
+ if (upper) {
+ mas_set_range(&mas, upper_index, upper_last);
+ ret = mas_store_gfp(&mas, upper, GFP_KERNEL);
+ if (ret != 0)
+ goto out;
+ upper = NULL;
+ }
+ }
+
+out:
+ mas_unlock(&mas);
+ kfree(lower);
+ kfree(upper);
+
+ return ret;
+}
+
+static int regcache_maple_sync(struct regmap *map, unsigned int min,
+ unsigned int max)
+{
+ struct maple_tree *mt = map->cache;
+ unsigned long *entry;
+ MA_STATE(mas, mt, min, max);
+ unsigned long lmin = min;
+ unsigned long lmax = max;
+ unsigned int r;
+ int ret;
+
+ map->cache_bypass = true;
+
+ rcu_read_lock();
+
+ mas_for_each(&mas, entry, max) {
+ for (r = max(mas.index, lmin); r <= min(mas.last, lmax); r++) {
+ ret = regcache_sync_val(map, r, entry[r - mas.index]);
+ if (ret != 0)
+ goto out;
+ }
+ }
+
+out:
+ rcu_read_unlock();
+
+ map->cache_bypass = false;
+
+ return ret;
+}
+
+static int regcache_maple_exit(struct regmap *map)
+{
+ struct maple_tree *mt = map->cache;
+ MA_STATE(mas, mt, 0, UINT_MAX);
+ unsigned int *entry;;
+
+ /* if we've already been called then just return */
+ if (!mt)
+ return 0;
+
+ mas_lock(&mas);
+ mas_for_each(&mas, entry, UINT_MAX)
+ kfree(entry);
+ __mt_destroy(mt);
+ mas_unlock(&mas);
+
+ kfree(mt);
+ map->cache = NULL;
+
+ return 0;
+}
+
+static int regcache_maple_init(struct regmap *map)
+{
+ struct maple_tree *mt;
+ int i;
+ int ret;
+
+ mt = kmalloc(sizeof(*mt), GFP_KERNEL);
+ if (!mt)
+ return -ENOMEM;
+ map->cache = mt;
+
+ mt_init(mt);
+
+ for (i = 0; i < map->num_reg_defaults; i++) {
+ ret = regcache_maple_write(map,
+ map->reg_defaults[i].reg,
+ map->reg_defaults[i].def);
+ if (ret)
+ goto err;
+ }
+
+ return 0;
+
+err:
+ regcache_maple_exit(map);
+ return ret;
+}
+
+struct regcache_ops regcache_maple_ops = {
+ .type = REGCACHE_MAPLE,
+ .name = "maple",
+ .init = regcache_maple_init,
+ .exit = regcache_maple_exit,
+ .read = regcache_maple_read,
+ .write = regcache_maple_write,
+ .drop = regcache_maple_drop,
+ .sync = regcache_maple_sync,
+};
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