reset: add TI SYSCON based reset driver

Add a reset-controller driver for performing reset management of
various devices present on the SoC, with the reset registers shared
between devices in a common register memory space. This driver uses
the syscon/regmap frameworks to actually implement the various reset
functionalities needed by the reset consumer devices.

Signed-off-by: Andrew F. Davis <afd@ti.com>
[s-anna@ti.com: add documentation, syscon name change]
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

3 files changed, 248 insertions, 0 deletions

diff --git a/drivers/reset/Kconfig b/drivers/reset/Kconfig
index ab37f4db9642..4be1b8c21f6f 100644
--- a/drivers/reset/Kconfig
+++ b/drivers/reset/Kconfig
@@ -17,6 +17,16 @@ if RESET_CONTROLLER
 config RESET_OXNAS
         bool
 
+config TI_SYSCON_RESET
+        tristate "TI SYSCON Reset Driver"
+        depends on HAS_IOMEM
+        select MFD_SYSCON
+        help
+          This enables the reset driver support for TI devices with
+          memory-mapped reset registers as part of a syscon device node. If
+          you wish to use the reset framework for such memory-mapped devices,
+          say Y here. Otherwise, say N.
+
 source "drivers/reset/sti/Kconfig"
 source "drivers/reset/hisilicon/Kconfig"
 
diff --git a/drivers/reset/Makefile b/drivers/reset/Makefile
index 03dc1bb7649e..5d65a93d3c43 100644
--- a/drivers/reset/Makefile
+++ b/drivers/reset/Makefile
@@ -10,3 +10,4 @@ obj-$(CONFIG_ARCH_HISI) += hisilicon/
 obj-$(CONFIG_ARCH_ZYNQ) += reset-zynq.o
 obj-$(CONFIG_ATH79) += reset-ath79.o
 obj-$(CONFIG_RESET_OXNAS) += reset-oxnas.o
+obj-$(CONFIG_TI_SYSCON_RESET) += reset-ti-syscon.o
diff --git a/drivers/reset/reset-ti-syscon.c b/drivers/reset/reset-ti-syscon.c
new file mode 100644
index 000000000000..47f0ffd3b013
--- /dev/null
+++ b/drivers/reset/reset-ti-syscon.c
@@ -0,0 +1,237 @@
+/*
+ * TI SYSCON regmap reset driver
+ *
+ * Copyright (C) 2015-2016 Texas Instruments Incorporated - http://www.ti.com/
+ *      Andrew F. Davis <afd@ti.com>
+ *      Suman Anna <afd@ti.com>
+ *
+ * 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.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/reset-controller.h>
+
+#include <dt-bindings/reset/ti-syscon.h>
+
+/**
+ * struct ti_syscon_reset_control - reset control structure
+ * @assert_offset: reset assert control register offset from syscon base
+ * @assert_bit: reset assert bit in the reset assert control register
+ * @deassert_offset: reset deassert control register offset from syscon base
+ * @deassert_bit: reset deassert bit in the reset deassert control register
+ * @status_offset: reset status register offset from syscon base
+ * @status_bit: reset status bit in the reset status register
+ * @flags: reset flag indicating how the (de)assert and status are handled
+ */
+struct ti_syscon_reset_control {
+        unsigned int assert_offset;
+        unsigned int assert_bit;
+        unsigned int deassert_offset;
+        unsigned int deassert_bit;
+        unsigned int status_offset;
+        unsigned int status_bit;
+        u32 flags;
+};
+
+/**
+ * struct ti_syscon_reset_data - reset controller information structure
+ * @rcdev: reset controller entity
+ * @regmap: regmap handle containing the memory-mapped reset registers
+ * @controls: array of reset controls
+ * @nr_controls: number of controls in control array
+ */
+struct ti_syscon_reset_data {
+        struct reset_controller_dev rcdev;
+        struct regmap *regmap;
+        struct ti_syscon_reset_control *controls;
+        unsigned int nr_controls;
+};
+
+#define to_ti_syscon_reset_data(rcdev)  \
+        container_of(rcdev, struct ti_syscon_reset_data, rcdev)
+
+/**
+ * ti_syscon_reset_assert() - assert device reset
+ * @rcdev: reset controller entity
+ * @id: ID of the reset to be asserted
+ *
+ * This function implements the reset driver op to assert a device's reset.
+ * This asserts the reset in a manner prescribed by the reset flags.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int ti_syscon_reset_assert(struct reset_controller_dev *rcdev,
+                                  unsigned long id)
+{
+        struct ti_syscon_reset_data *data = to_ti_syscon_reset_data(rcdev);
+        struct ti_syscon_reset_control *control;
+        unsigned int mask, value;
+
+        if (id >= data->nr_controls)
+                return -EINVAL;
+
+        control = &data->controls[id];
+
+        if (control->flags & ASSERT_NONE)
+                return -ENOTSUPP; /* assert not supported for this reset */
+
+        mask = BIT(control->assert_bit);
+        value = (control->flags & ASSERT_SET) ? mask : 0x0;
+
+        return regmap_update_bits(data->regmap, control->assert_offset, mask, value);
+}
+
+/**
+ * ti_syscon_reset_deassert() - deassert device reset
+ * @rcdev: reset controller entity
+ * @id: ID of reset to be deasserted
+ *
+ * This function implements the reset driver op to deassert a device's reset.
+ * This deasserts the reset in a manner prescribed by the reset flags.
+ *
+ * Return: 0 for successful request, else a corresponding error value
+ */
+static int ti_syscon_reset_deassert(struct reset_controller_dev *rcdev,
+                                    unsigned long id)
+{
+        struct ti_syscon_reset_data *data = to_ti_syscon_reset_data(rcdev);
+        struct ti_syscon_reset_control *control;
+        unsigned int mask, value;
+
+        if (id >= data->nr_controls)
+                return -EINVAL;
+
+        control = &data->controls[id];
+
+        if (control->flags & DEASSERT_NONE)
+                return -ENOTSUPP; /* deassert not supported for this reset */
+
+        mask = BIT(control->deassert_bit);
+        value = (control->flags & DEASSERT_SET) ? mask : 0x0;
+
+        return regmap_update_bits(data->regmap, control->deassert_offset, mask, value);
+}
+
+/**
+ * ti_syscon_reset_status() - check device reset status
+ * @rcdev: reset controller entity
+ * @id: ID of the reset for which the status is being requested
+ *
+ * This function implements the reset driver op to return the status of a
+ * device's reset.
+ *
+ * Return: 0 if reset is deasserted, true if reset is asserted, else a
+ * corresponding error value
+ */
+static int ti_syscon_reset_status(struct reset_controller_dev *rcdev,
+                                  unsigned long id)
+{
+        struct ti_syscon_reset_data *data = to_ti_syscon_reset_data(rcdev);
+        struct ti_syscon_reset_control *control;
+        unsigned int reset_state;
+        int ret;
+
+        if (id >= data->nr_controls)
+                return -EINVAL;
+
+        control = &data->controls[id];
+
+        if (control->flags & STATUS_NONE)
+                return -ENOTSUPP; /* status not supported for this reset */
+
+        ret = regmap_read(data->regmap, control->status_offset, &reset_state);
+        if (ret)
+                return ret;
+
+        return (reset_state & BIT(control->status_bit)) &&
+                        (control->flags & STATUS_SET);
+}
+
+static struct reset_control_ops ti_syscon_reset_ops = {
+        .assert         = ti_syscon_reset_assert,
+        .deassert       = ti_syscon_reset_deassert,
+        .status         = ti_syscon_reset_status,
+};
+
+static int ti_syscon_reset_probe(struct platform_device *pdev)
+{
+        struct device *dev = &pdev->dev;
+        struct device_node *np = dev->of_node;
+        struct ti_syscon_reset_data *data;
+        struct regmap *regmap;
+        const __be32 *list;
+        struct ti_syscon_reset_control *controls;
+        int size, nr_controls, i;
+
+        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+
+        regmap = syscon_node_to_regmap(np->parent);
+        if (IS_ERR(regmap))
+                return PTR_ERR(regmap);
+
+        list = of_get_property(np, "ti,reset-bits", &size);
+        if (!list || (size / sizeof(*list)) % 7 != 0) {
+                dev_err(dev, "invalid DT reset description\n");
+                return -EINVAL;
+        }
+
+        nr_controls = (size / sizeof(*list)) / 7;
+        controls = devm_kzalloc(dev, nr_controls * sizeof(*controls), GFP_KERNEL);
+        if (!controls)
+                return -ENOMEM;
+
+        for (i = 0; i < nr_controls; i++) {
+                controls[i].assert_offset = be32_to_cpup(list++);
+                controls[i].assert_bit = be32_to_cpup(list++);
+                controls[i].deassert_offset = be32_to_cpup(list++);
+                controls[i].deassert_bit = be32_to_cpup(list++);
+                controls[i].status_offset = be32_to_cpup(list++);
+                controls[i].status_bit = be32_to_cpup(list++);
+                controls[i].flags = be32_to_cpup(list++);
+        }
+
+        data->rcdev.ops = &ti_syscon_reset_ops;
+        data->rcdev.owner = THIS_MODULE;
+        data->rcdev.of_node = np;
+        data->rcdev.nr_resets = nr_controls;
+        data->regmap = regmap;
+        data->controls = controls;
+        data->nr_controls = nr_controls;
+
+        platform_set_drvdata(pdev, data);
+
+        return devm_reset_controller_register(dev, &data->rcdev);
+}
+
+static const struct of_device_id ti_syscon_reset_of_match[] = {
+        { .compatible = "ti,syscon-reset", },
+        { /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, ti_syscon_reset_of_match);
+
+static struct platform_driver ti_syscon_reset_driver = {
+        .probe = ti_syscon_reset_probe,
+        .driver = {
+                .name = "ti-syscon-reset",
+                .of_match_table = ti_syscon_reset_of_match,
+        },
+};
+module_platform_driver(ti_syscon_reset_driver);
+
+MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
+MODULE_AUTHOR("Suman Anna <s-anna@ti.com>");
+MODULE_DESCRIPTION("TI SYSCON Regmap Reset Driver");
+MODULE_LICENSE("GPL v2");