[RFC v2 2/2] mux: mmio-based syscon mux controller

[Philipp Zabel]

This adds a driver for mmio-based syscon multiplexers controlled by a
single bitfield in a syscon register range.

Signed-off-by: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>
---
Changes since v1:
 - Renamed MUX_SYSCON to MUX_MMIO. Instead of obtaining the regmap via syscon,
   this could just as well map its own MMIO register range if a reg property
   was added.
 - Replaced reg, bit-mask, and bit-shift properties with mux-reg-masks array
   to allow defining multiple mux bit-fields per mmio-mux instance.
 - Changed mux-control-cells value to <1>, the cell value is an index into
   the mux-reg-masks array.
 - Replaced idle-state with idle-states array.
 - Stopped clobbering mux->cached_state, that is internal to the mux core.
---
 drivers/mux/Kconfig    |  13 ++++
 drivers/mux/Makefile   |   1 +
 drivers/mux/mux-mmio.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 176 insertions(+)
 create mode 100644 drivers/mux/mux-mmio.c

diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
index 34b8284d6d29e..e2bee25a1586e 100644
--- a/drivers/mux/Kconfig
+++ b/drivers/mux/Kconfig
@@ -43,4 +43,17 @@ config MUX_GPIO
 	  To compile the driver as a module, choose M here: the module will
 	  be called mux-gpio.
 
+config MUX_MMIO
+	tristate "MMIO register bitfield-controlled Multiplexer"
+	depends on OF && MFD_SYSCON
+	help
+	  MMIO register bitfield-controlled Multiplexer controller.
+
+	  The driver builds a single multiplexer controller using a bitfield
+	  in a syscon register. For N bit wide bitfields, there will be 2^N
+	  possible multiplexer states.
+
+	  To compile the driver as a module, choose M here: the module will
+	  be called mux-mmio.
+
 endif
diff --git a/drivers/mux/Makefile b/drivers/mux/Makefile
index b00a7d37d2fbe..6bac5b0fea137 100644
--- a/drivers/mux/Makefile
+++ b/drivers/mux/Makefile
@@ -5,3 +5,4 @@
 obj-$(CONFIG_MULTIPLEXER)	+= mux-core.o
 obj-$(CONFIG_MUX_ADG792A)	+= mux-adg792a.o
 obj-$(CONFIG_MUX_GPIO)		+= mux-gpio.o
+obj-$(CONFIG_MUX_MMIO)		+= mux-mmio.o
diff --git a/drivers/mux/mux-mmio.c b/drivers/mux/mux-mmio.c
new file mode 100644
index 0000000000000..0b011fb59f99b
--- /dev/null
+++ b/drivers/mux/mux-mmio.c
@@ -0,0 +1,162 @@
+/*
+ * MMIO register bitfield-controlled multiplexer driver
+ *
+ * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@xxxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/err.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/mux/driver.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/property.h>
+#include <linux/regmap.h>
+
+static int mux_mmio_set(struct mux_control *mux, int state)
+{
+	struct regmap_field **fields = mux_chip_priv(mux->chip);
+	int index = mux - mux->chip->mux;
+
+	return regmap_field_write(fields[index], state);
+}
+
+static const struct mux_control_ops mux_mmio_ops = {
+	.set = mux_mmio_set,
+};
+
+static const struct of_device_id mux_mmio_dt_ids[] = {
+	{ .compatible = "mmio-mux", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mux_mmio_dt_ids);
+
+static int mux_mmio_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct device_node *np = dev->of_node;
+	struct regmap_field **fields;
+	struct mux_chip *mux_chip;
+	struct regmap *regmap;
+	s32 *idle_states;
+	u32 *reg_masks;
+	int num_fields;
+	int ret;
+	int i;
+
+	regmap = syscon_node_to_regmap(np->parent);
+	if (IS_ERR(regmap)) {
+		ret = PTR_ERR(regmap);
+		dev_err(dev, "failed to get syscon regmap: %d\n", ret);
+		return ret;
+	}
+
+	ret = of_property_count_u32_elems(np, "mux-reg-masks");
+	if (ret == 0 || ret % 2)
+		ret = -EINVAL;
+	if (ret > 0) {
+		num_fields = ret / 2;
+
+		reg_masks = devm_kmalloc(dev, ret * sizeof(u32), GFP_KERNEL);
+		if (!reg_masks)
+			return -ENOMEM;
+
+		ret = of_property_read_u32_array(np, "mux-reg-masks",
+						 reg_masks, ret);
+	}
+	if (ret < 0) {
+		dev_err(dev, "mux-reg-masks property missing or invalid: %d\n",
+			ret);
+		return ret;
+	}
+
+	mux_chip = devm_mux_chip_alloc(dev, num_fields, num_fields *
+				       sizeof(*fields));
+	if (IS_ERR(mux_chip))
+		return PTR_ERR(mux_chip);
+
+	fields = mux_chip_priv(mux_chip);
+
+	for (i = 0; i < num_fields; i++) {
+		struct mux_control *mux = &mux_chip->mux[i];
+		struct reg_field field;
+		u32 *reg_mask = reg_masks + 2 * i;
+		int bits;
+
+		field.reg = reg_mask[0];
+		field.msb = fls(reg_mask[1]) - 1;
+		field.lsb = ffs(reg_mask[1]) - 1;
+		bits = 1 + field.msb - field.lsb;
+
+		fields[i] = devm_regmap_field_alloc(&pdev->dev, regmap, field);
+		if (IS_ERR(fields[i])) {
+			ret = PTR_ERR(fields[i]);
+			dev_err(&pdev->dev, "failed to get bit-field %d: %d\n",
+				i, ret);
+			return ret;
+		}
+
+		mux->states = 1 << bits;
+	}
+
+	devm_kfree(dev, reg_masks);
+
+	if (of_find_property(np, "idle-states", NULL)) {
+		ret = of_property_count_u32_elems(np, "idle-states");
+		if (ret == num_fields) {
+			idle_states = devm_kmalloc(dev, ret * sizeof(s32),
+						   GFP_KERNEL);
+			if (!idle_states)
+				return -ENOMEM;
+
+			ret = of_property_read_u32_array(np, "idle-states",
+							 idle_states, ret);
+		} else {
+			idle_states = NULL;
+			if (ret >= 0)
+				ret = -EINVAL;
+		}
+		if (ret < 0) {
+			dev_err(dev, "idle-states property invalid: %d\n", ret);
+			return ret;
+		}
+
+		for (i = 0; i < num_fields; i++) {
+			struct mux_control *mux = &mux_chip->mux[i];
+
+			if (idle_states[i] != MUX_IDLE_AS_IS) {
+				if (idle_states[i] < 0 ||
+				    idle_states[i] >= mux->states) {
+					dev_err(dev, "invalid idle-state %u\n",
+						idle_states[i]);
+					return -EINVAL;
+				}
+
+				mux->idle_state = idle_states[i];
+			}
+		}
+
+		devm_kfree(dev, idle_states);
+	}
+
+	mux_chip->ops = &mux_mmio_ops;
+
+	return devm_mux_chip_register(dev, mux_chip);
+}
+
+static struct platform_driver mux_mmio_driver = {
+	.driver = {
+		.name = "mmio-mux",
+		.of_match_table	= of_match_ptr(mux_mmio_dt_ids),
+	},
+	.probe = mux_mmio_probe,
+};
+module_platform_driver(mux_mmio_driver);
+
+MODULE_DESCRIPTION("MMIO register bitfield-controlled multiplexer driver");
+MODULE_AUTHOR("Philipp Zabel <p.zabel@xxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
-- 
2.11.0