mux: mmio-based syscon mux controller

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

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 155 insertions, 0 deletions

diff --git a/drivers/mux/Kconfig b/drivers/mux/Kconfig
index c4d050645605..e8f1df74644c 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) || COMPILE_TEST
+        help
+          MMIO register bitfield-controlled Multiplexer controller.
+
+          The driver builds multiplexer controllers for bitfields 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 b00a7d37d2fb..6bac5b0fea13 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 000000000000..37c1de359a70
--- /dev/null
+++ b/drivers/mux/mux-mmio.c
@@ -0,0 +1,141 @@
+/*
+ * MMIO register bitfield-controlled multiplexer driver
+ *
+ * Copyright (C) 2017 Pengutronix, Philipp Zabel <kernel@pengutronix.de>
+ *
+ * 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/bitops.h>
+#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);
+
+        return regmap_field_write(fields[mux_control_get_index(mux)], 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;
+        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 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) {
+                dev_err(dev, "mux-reg-masks property missing or invalid: %d\n",
+                        ret);
+                return ret;
+        }
+        num_fields = ret / 2;
+
+        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;
+                s32 idle_state = MUX_IDLE_AS_IS;
+                u32 reg, mask;
+                int bits;
+
+                ret = of_property_read_u32_index(np, "mux-reg-masks",
+                                                 2 * i, &reg);
+                if (!ret)
+                        ret = of_property_read_u32_index(np, "mux-reg-masks",
+                                                         2 * i + 1, &mask);
+                if (ret < 0) {
+                        dev_err(dev, "bitfield %d: failed to read mux-reg-masks property: %d\n",
+                                i, ret);
+                        return ret;
+                }
+
+                field.reg = reg;
+                field.msb = fls(mask) - 1;
+                field.lsb = ffs(mask) - 1;
+
+                if (mask != GENMASK(field.msb, field.lsb)) {
+                        dev_err(dev, "bitfield %d: invalid mask 0x%x\n",
+                                i, mask);
+                        return -EINVAL;
+                }
+
+                fields[i] = devm_regmap_field_alloc(dev, regmap, field);
+                if (IS_ERR(fields[i])) {
+                        ret = PTR_ERR(fields[i]);
+                        dev_err(dev, "bitfield %d: failed allocate: %d\n",
+                                i, ret);
+                        return ret;
+                }
+
+                bits = 1 + field.msb - field.lsb;
+                mux->states = 1 << bits;
+
+                of_property_read_u32_index(np, "idle-states", i,
+                                           (u32 *)&idle_state);
+                if (idle_state != MUX_IDLE_AS_IS) {
+                        if (idle_state < 0 || idle_state >= mux->states) {
+                                dev_err(dev, "bitfield: %d: out of range idle state %d\n",
+                                        i, idle_state);
+                                return -EINVAL;
+                        }
+
+                        mux->idle_state = idle_state;
+                }
+        }
+
+        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@pengutronix.de>");
+MODULE_LICENSE("GPL v2");