Prepare a single regmap covering the entire SPI address space of the
SJA1105 and SJA1110 switches which can be given to MDIO buses, XPCS,
irqchip drivers etc.

This regmap is zero-based, can access the entire switch address space,
and child devices are supposed to access their respective memory region
with the help of struct resource (IORESOURCE_REG, to be precise).

Nothing is currently done with the regmap, it is just allocated and
added to the device's devres list, so it doesn't need to be freed.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
 drivers/net/dsa/sja1105/sja1105.h      |  4 ++
 drivers/net/dsa/sja1105/sja1105_main.c |  6 +++
 drivers/net/dsa/sja1105/sja1105_spi.c  | 58 ++++++++++++++++++++++++++
 3 files changed, 68 insertions(+)

diff --git a/drivers/net/dsa/sja1105/sja1105.h b/drivers/net/dsa/sja1105/sja1105.h
index dceb96ae9c83..e952917b67b6 100644
--- a/drivers/net/dsa/sja1105/sja1105.h
+++ b/drivers/net/dsa/sja1105/sja1105.h
@@ -11,6 +11,8 @@
 #include <linux/dsa/8021q.h>
 #include <net/dsa.h>
 #include <linux/mutex.h>
+#include <linux/regmap.h>
+
 #include "sja1105_static_config.h"
 
 #define SJA1105ET_FDB_BIN_SIZE		4
@@ -273,6 +275,7 @@ struct sja1105_private {
 	u8 ts_id;
 	/* Serializes access to the dynamic config interface */
 	struct mutex dynamic_config_lock;
+	struct regmap *regmap;
 	struct devlink_region **regions;
 	struct sja1105_cbs_entry *cbs;
 	struct mii_bus *mdio_base_t1;
@@ -338,6 +341,7 @@ int static_config_buf_prepare_for_upload(struct sja1105_private *priv,
 int sja1105_static_config_upload(struct sja1105_private *priv);
 int sja1105_inhibit_tx(const struct sja1105_private *priv,
 		       unsigned long port_bitmap, bool tx_inhibited);
+int sja1105_create_regmap(struct sja1105_private *priv);
 
 extern const struct sja1105_info sja1105e_info;
 extern const struct sja1105_info sja1105t_info;
diff --git a/drivers/net/dsa/sja1105/sja1105_main.c b/drivers/net/dsa/sja1105/sja1105_main.c
index 9f62cc7e1bd1..622264c13fdb 100644
--- a/drivers/net/dsa/sja1105/sja1105_main.c
+++ b/drivers/net/dsa/sja1105/sja1105_main.c
@@ -3318,6 +3318,12 @@ static int sja1105_probe(struct spi_device *spi)
 
 	priv->info = of_device_get_match_data(dev);
 
+	rc = sja1105_create_regmap(priv);
+	if (rc < 0) {
+		dev_err(dev, "Failed to create regmap: %pe\n", ERR_PTR(rc));
+		return rc;
+	}
+
 	/* Detect hardware device */
 	rc = sja1105_check_device_id(priv);
 	if (rc < 0) {
diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
index 834b5c1b4db0..cfc76af8a65b 100644
--- a/drivers/net/dsa/sja1105/sja1105_spi.c
+++ b/drivers/net/dsa/sja1105/sja1105_spi.c
@@ -408,6 +408,64 @@ int sja1105_static_config_upload(struct sja1105_private *priv)
 	return rc;
 }
 
+static int sja1105_regmap_bus_reg_read(void *ctx, unsigned int reg,
+				       unsigned int *val)
+{
+	struct sja1105_private *priv = ctx;
+	u32 tmp;
+	int rc;
+
+	rc = sja1105_xfer_u32(priv, SPI_READ, SJA1110_SPI_ADDR(reg), &tmp,
+			      NULL);
+	if (rc)
+		return rc;
+
+	*val = tmp;
+
+	return 0;
+}
+
+static int sja1105_regmap_bus_reg_write(void *ctx, unsigned int reg,
+					unsigned int val)
+{
+	struct sja1105_private *priv = ctx;
+	u32 tmp = val;
+
+	return sja1105_xfer_u32(priv, SPI_WRITE, SJA1110_SPI_ADDR(reg), &tmp,
+				NULL);
+}
+
+static struct regmap_bus sja1105_regmap_bus = {
+	.reg_read = sja1105_regmap_bus_reg_read,
+	.reg_write = sja1105_regmap_bus_reg_write,
+	.reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
+	.val_format_endian_default = REGMAP_ENDIAN_NATIVE,
+};
+
+/* The primary purpose of this is to pass it to child devices,
+ * not to abstract SPI access for the main driver.
+ */
+int sja1105_create_regmap(struct sja1105_private *priv)
+{
+	struct device *dev = &priv->spidev->dev;
+	struct regmap_config regmap_config = {
+		.name = "switch",
+		.reg_bits = 32,
+		.val_bits = 32,
+		.reg_stride = 4,
+	};
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init(dev, &sja1105_regmap_bus, priv,
+				  &regmap_config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	priv->regmap = regmap;
+
+	return 0;
+}
+
 static const struct sja1105_regs sja1105et_regs = {
 	.device_id = 0x0,
 	.prod_id = 0x100BC3,
-- 
2.34.1