[PATCH 08/12] regmap: indirect: Add indirect regmap support

["Ilpo Järvinen" <ilpo.jarvinen@linux.intel.com>]

Add support for indirect register access via a regmap interface.

Indirect register access is a generic way to access registers directly.
One use case is accessing registers on Intel FPGA IPs with e.g. PMCI or
HSSI.

Co-developed-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/base/regmap/Kconfig           |   3 +
 drivers/base/regmap/Makefile          |   1 +
 drivers/base/regmap/regmap-indirect.c | 128 ++++++++++++++++++++++++++
 include/linux/regmap.h                |  55 +++++++++++
 4 files changed, 187 insertions(+)
 create mode 100644 drivers/base/regmap/regmap-indirect.c

diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
index 159bac6c5046..94e5ca5434cf 100644
--- a/drivers/base/regmap/Kconfig
+++ b/drivers/base/regmap/Kconfig
@@ -65,3 +65,6 @@ config REGMAP_I3C
 config REGMAP_SPI_AVMM
 	tristate
 	depends on SPI
+
+config REGMAP_INDIRECT
+	tristate
diff --git a/drivers/base/regmap/Makefile b/drivers/base/regmap/Makefile
index 11facb32a027..6221a4740806 100644
--- a/drivers/base/regmap/Makefile
+++ b/drivers/base/regmap/Makefile
@@ -20,3 +20,4 @@ obj-$(CONFIG_REGMAP_SCCB) += regmap-sccb.o
 obj-$(CONFIG_REGMAP_I3C) += regmap-i3c.o
 obj-$(CONFIG_REGMAP_SPI_AVMM) += regmap-spi-avmm.o
 obj-$(CONFIG_REGMAP_MDIO) += regmap-mdio.o
+obj-$(CONFIG_REGMAP_INDIRECT) += regmap-indirect.o
diff --git a/drivers/base/regmap/regmap-indirect.c b/drivers/base/regmap/regmap-indirect.c
new file mode 100644
index 000000000000..3ceb0c044c7c
--- /dev/null
+++ b/drivers/base/regmap/regmap-indirect.c
@@ -0,0 +1,128 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Indirect Register Access.
+ *
+ * Copyright (C) 2020-2022 Intel Corporation, Inc.
+ */
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/regmap.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+
+struct indirect_ctx {
+	void __iomem *base;
+	struct device *dev;
+	const struct regmap_indirect_cfg *indirect_cfg;
+};
+
+static int indirect_bus_idle_cmd(struct indirect_ctx *ctx)
+{
+	unsigned int cmd;
+	int ret;
+
+	writel(ctx->indirect_cfg->idle_cmd, ctx->base + ctx->indirect_cfg->cmd_offset);
+
+	ret = readl_poll_timeout(ctx->base + ctx->indirect_cfg->cmd_offset, cmd,
+				 cmd == ctx->indirect_cfg->idle_cmd,
+				 ctx->indirect_cfg->sleep_us, ctx->indirect_cfg->timeout_us);
+	if (ret)
+		dev_err(ctx->dev, "timed out waiting idle cmd (residual cmd=0x%x)\n", cmd);
+
+	return ret;
+}
+
+static int indirect_bus_reg_read(void *context, unsigned int reg,
+				     unsigned int *val)
+{
+	struct indirect_ctx *ctx = context;
+	unsigned int cmd, ack, tmpval;
+	int ret;
+
+	cmd = readl(ctx->base + ctx->indirect_cfg->cmd_offset);
+	if (cmd != ctx->indirect_cfg->idle_cmd)
+		dev_warn(ctx->dev, "residual cmd 0x%x on read entry\n", cmd);
+
+	writel(reg, ctx->base + ctx->indirect_cfg->addr_offset);
+	writel(ctx->indirect_cfg->read_cmd, ctx->base + ctx->indirect_cfg->cmd_offset);
+
+	ret = readl_poll_timeout(ctx->base + ctx->indirect_cfg->ack_offset, ack,
+				 (ack & ctx->indirect_cfg->ack_mask) == ctx->indirect_cfg->ack_mask,
+				 ctx->indirect_cfg->sleep_us, ctx->indirect_cfg->timeout_us);
+	if (ret) {
+		dev_err(ctx->dev, "read timed out on reg 0x%x ack 0x%x\n", reg, ack);
+		goto out;
+	}
+
+	tmpval = readl(ctx->base + ctx->indirect_cfg->read_offset);
+
+	if (indirect_bus_idle_cmd(ctx)) {
+		if (!ret)
+			ret = -ETIMEDOUT;
+		goto out;
+	}
+
+	*val = tmpval;
+out:
+	return ret;
+}
+
+static int indirect_bus_reg_write(void *context, unsigned int reg,
+				      unsigned int val)
+{
+	struct indirect_ctx *ctx = context;
+	unsigned int cmd, ack;
+	int ret;
+
+	cmd = readl(ctx->base + ctx->indirect_cfg->cmd_offset);
+	if (cmd != ctx->indirect_cfg->idle_cmd)
+		dev_warn(ctx->dev, "residual cmd 0x%x on write entry\n", cmd);
+
+	writel(val, ctx->base + ctx->indirect_cfg->write_offset);
+	writel(reg, ctx->base + ctx->indirect_cfg->addr_offset);
+	writel(ctx->indirect_cfg->write_cmd, ctx->base + ctx->indirect_cfg->cmd_offset);
+
+	ret = readl_poll_timeout(ctx->base + ctx->indirect_cfg->ack_offset, ack,
+				 (ack & ctx->indirect_cfg->ack_mask) == ctx->indirect_cfg->ack_mask,
+				 ctx->indirect_cfg->sleep_us, ctx->indirect_cfg->timeout_us);
+	if (ret)
+		dev_err(ctx->dev, "write timed out on reg 0x%x ack 0x%x\n", reg, ack);
+
+	if (indirect_bus_idle_cmd(ctx)) {
+		if (!ret)
+			ret = -ETIMEDOUT;
+	}
+
+	return ret;
+}
+
+static const struct regmap_bus indirect_bus = {
+	.reg_write = indirect_bus_reg_write,
+	.reg_read =  indirect_bus_reg_read,
+};
+
+struct regmap *__devm_regmap_init_indirect(struct device *dev,
+					   void __iomem *base,
+					   struct regmap_config *cfg,
+					   struct lock_class_key *lock_key,
+					   const char *lock_name)
+{
+	struct indirect_ctx *ctx;
+
+	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
+	if (!ctx)
+		return NULL;
+
+	ctx->base = base;
+	ctx->dev = dev;
+	ctx->indirect_cfg = cfg->indirect_cfg;
+
+	return __devm_regmap_init(dev, &indirect_bus, ctx, cfg, lock_key, lock_name);
+}
+EXPORT_SYMBOL_GPL(__devm_regmap_init_indirect);
+
+MODULE_DESCRIPTION("Indirect Register Access");
+MODULE_AUTHOR("Intel Corporation");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/regmap.h b/include/linux/regmap.h
index ca3434dca3a0..adaa7bca4f60 100644
--- a/include/linux/regmap.h
+++ b/include/linux/regmap.h
@@ -190,6 +190,41 @@ enum regmap_endian {
 	REGMAP_ENDIAN_NATIVE,
 };
 
+/**
+ * struct regmap_indirect_cfg - A configuration for indirect register access
+ *
+ * @cmd_offset: Command register offset
+ * @idle_cmd: Idle command
+ * @read_cmd: Read command
+ * @write_cmd: Write command
+ *
+ * @ack_offset: Command acknowledgment register offset
+ * @ack_mask: Command acknowledgment bit mask
+ *
+ * @addr_offset: Address register offset
+ * @read_offset: Read register offset
+ * @write_offset: Write register offset
+ *
+ * @sleep_us: Command wait sleep (usecs)
+ * @timeout_us: Command timeout (usecs)
+ */
+struct regmap_indirect_cfg {
+	unsigned int cmd_offset;
+	u32 idle_cmd;
+	u32 read_cmd;
+	u32 write_cmd;
+
+	unsigned int ack_offset;
+	u32 ack_mask;
+
+	unsigned int addr_offset;
+	unsigned int read_offset;
+	unsigned int write_offset;
+
+	unsigned long sleep_us;
+	unsigned long timeout_us;
+};
+
 /**
  * struct regmap_range - A register range, used for access related checks
  *                       (readable/writeable/volatile/precious checks)
@@ -431,6 +466,8 @@ struct regmap_config {
 	const struct regmap_range_cfg *ranges;
 	unsigned int num_ranges;
 
+	const struct regmap_indirect_cfg *indirect_cfg;
+
 	bool use_hwlock;
 	bool use_raw_spinlock;
 	unsigned int hwlock_id;
@@ -693,6 +730,12 @@ struct regmap *__devm_regmap_init_spi_avmm(struct spi_device *spi,
 					   const struct regmap_config *config,
 					   struct lock_class_key *lock_key,
 					   const char *lock_name);
+struct regmap *__devm_regmap_init_indirect(struct device *dev,
+					   void __iomem *base,
+					   struct regmap_config *cfg,
+					   struct lock_class_key *lock_key,
+					   const char *lock_name);
+
 /*
  * Wrapper for regmap_init macros to include a unique lockdep key and name
  * for each call. No-op if CONFIG_LOCKDEP is not set.
@@ -1148,6 +1191,18 @@ bool regmap_ac97_default_volatile(struct device *dev, unsigned int reg);
 	__regmap_lockdep_wrapper(__devm_regmap_init_spi_avmm, #config,	\
 				 spi, config)
 
+/**
+ * devm_regmap_init_indirect - create a regmap for indirect register access
+ * @dev: device creating the regmap
+ * @base: __iomem point to base of memory with mailbox
+ * @cfg: regmap_config describing interface
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+#define devm_regmap_init_indirect(dev, base, config)			\
+	__regmap_lockdep_wrapper(__devm_regmap_init_indirect, #config,	\
+				 dev, base, config)
+
 int regmap_mmio_attach_clk(struct regmap *map, struct clk *clk);
 void regmap_mmio_detach_clk(struct regmap *map);
 void regmap_exit(struct regmap *map);
-- 
2.30.2