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+/*
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+ * Texas Instrument's System Control Interface (TI-SCI) reset driver
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+ *
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+ * Copyright (C) 2015-2017 Texas Instruments Incorporated - http://www.ti.com/
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+ * Andrew F. Davis <afd@ti.com>
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+ *
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+ * This program is free software; you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License version 2 as
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+ * published by the Free Software Foundation.
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+ *
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+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
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+ * kind, whether express or implied; without even the implied warranty
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+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ */
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+
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+#include <linux/idr.h>
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+#include <linux/module.h>
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+#include <linux/mutex.h>
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+#include <linux/of.h>
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+#include <linux/platform_device.h>
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+#include <linux/reset-controller.h>
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+#include <linux/soc/ti/ti_sci_protocol.h>
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+
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+/**
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+ * struct ti_sci_reset_control - reset control structure
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+ * @dev_id: SoC-specific device identifier
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+ * @reset_mask: reset mask to use for toggling reset
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+ * @lock: synchronize reset_mask read-modify-writes
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+ */
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+struct ti_sci_reset_control {
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+ u32 dev_id;
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+ u32 reset_mask;
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+ struct mutex lock;
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+};
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+
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+/**
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+ * struct ti_sci_reset_data - reset controller information structure
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+ * @rcdev: reset controller entity
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+ * @dev: reset controller device pointer
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+ * @sci: TI SCI handle used for communication with system controller
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+ * @idr: idr structure for mapping ids to reset control structures
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+ */
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+struct ti_sci_reset_data {
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+ struct reset_controller_dev rcdev;
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+ struct device *dev;
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+ const struct ti_sci_handle *sci;
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+ struct idr idr;
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+};
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+
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+#define to_ti_sci_reset_data(p) \
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+ container_of((p), struct ti_sci_reset_data, rcdev)
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+
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+/**
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+ * ti_sci_reset_set() - program a device's reset
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+ * @rcdev: reset controller entity
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+ * @id: ID of the reset to toggle
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+ * @assert: boolean flag to indicate assert or deassert
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+ *
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+ * This is a common internal function used to assert or deassert a device's
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+ * reset using the TI SCI protocol. The device's reset is asserted if the
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+ * @assert argument is true, or deasserted if @assert argument is false.
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+ * The mechanism itself is a read-modify-write procedure, the current device
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+ * reset register is read using a TI SCI device operation, the new value is
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+ * set or un-set using the reset's mask, and the new reset value written by
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+ * using another TI SCI device operation.
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+ *
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+ * Return: 0 for successful request, else a corresponding error value
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+ */
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+static int ti_sci_reset_set(struct reset_controller_dev *rcdev,
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+ unsigned long id, bool assert)
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+{
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+ struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
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+ const struct ti_sci_handle *sci = data->sci;
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+ const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
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+ struct ti_sci_reset_control *control;
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+ u32 reset_state;
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+ int ret;
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+
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+ control = idr_find(&data->idr, id);
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+ if (!control)
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+ return -EINVAL;
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+
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+ mutex_lock(&control->lock);
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+
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+ ret = dev_ops->get_device_resets(sci, control->dev_id, &reset_state);
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+ if (ret)
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+ goto out;
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+
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+ if (assert)
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+ reset_state |= control->reset_mask;
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+ else
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+ reset_state &= ~control->reset_mask;
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+
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+ ret = dev_ops->set_device_resets(sci, control->dev_id, reset_state);
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+out:
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+ mutex_unlock(&control->lock);
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+
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+ return ret;
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+}
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+
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+/**
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+ * ti_sci_reset_assert() - assert device reset
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+ * @rcdev: reset controller entity
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+ * @id: ID of the reset to be asserted
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+ *
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+ * This function implements the reset driver op to assert a device's reset
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+ * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
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+ * with the corresponding parameters as passed in, but with the @assert
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+ * argument set to true for asserting the reset.
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+ *
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+ * Return: 0 for successful request, else a corresponding error value
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+ */
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+static int ti_sci_reset_assert(struct reset_controller_dev *rcdev,
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+ unsigned long id)
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+{
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+ return ti_sci_reset_set(rcdev, id, true);
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+}
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+
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+/**
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+ * ti_sci_reset_deassert() - deassert device reset
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+ * @rcdev: reset controller entity
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+ * @id: ID of the reset to be deasserted
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+ *
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+ * This function implements the reset driver op to deassert a device's reset
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+ * using the TI SCI protocol. This invokes the function ti_sci_reset_set()
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+ * with the corresponding parameters as passed in, but with the @assert
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+ * argument set to false for deasserting the reset.
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+ *
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+ * Return: 0 for successful request, else a corresponding error value
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+ */
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+static int ti_sci_reset_deassert(struct reset_controller_dev *rcdev,
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+ unsigned long id)
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+{
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+ return ti_sci_reset_set(rcdev, id, false);
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+}
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+
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+/**
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+ * ti_sci_reset_status() - check device reset status
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+ * @rcdev: reset controller entity
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+ * @id: ID of reset to be checked
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+ *
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+ * This function implements the reset driver op to return the status of a
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+ * device's reset using the TI SCI protocol. The reset register value is read
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+ * by invoking the TI SCI device operation .get_device_resets(), and the
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+ * status of the specific reset is extracted and returned using this reset's
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+ * reset mask.
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+ *
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+ * Return: 0 if reset is deasserted, or a non-zero value if reset is asserted
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+ */
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+static int ti_sci_reset_status(struct reset_controller_dev *rcdev,
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+ unsigned long id)
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+{
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+ struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
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+ const struct ti_sci_handle *sci = data->sci;
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+ const struct ti_sci_dev_ops *dev_ops = &sci->ops.dev_ops;
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+ struct ti_sci_reset_control *control;
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+ u32 reset_state;
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+ int ret;
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+
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+ control = idr_find(&data->idr, id);
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+ if (!control)
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+ return -EINVAL;
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+
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+ ret = dev_ops->get_device_resets(sci, control->dev_id, &reset_state);
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+ if (ret)
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+ return ret;
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+
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+ return reset_state & control->reset_mask;
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+}
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+
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+static const struct reset_control_ops ti_sci_reset_ops = {
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+ .assert = ti_sci_reset_assert,
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+ .deassert = ti_sci_reset_deassert,
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+ .status = ti_sci_reset_status,
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+};
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+
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+/**
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+ * ti_sci_reset_of_xlate() - translate a set of OF arguments to a reset ID
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+ * @rcdev: reset controller entity
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+ * @reset_spec: OF reset argument specifier
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+ *
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+ * This function performs the translation of the reset argument specifier
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+ * values defined in a reset consumer device node. The function allocates a
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+ * reset control structure for that device reset, and will be used by the
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+ * driver for performing any reset functions on that reset. An idr structure
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+ * is allocated and used to map to the reset control structure. This idr
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+ * is used by the driver to do reset lookups.
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+ *
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+ * Return: 0 for successful request, else a corresponding error value
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+ */
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+static int ti_sci_reset_of_xlate(struct reset_controller_dev *rcdev,
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+ const struct of_phandle_args *reset_spec)
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+{
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+ struct ti_sci_reset_data *data = to_ti_sci_reset_data(rcdev);
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+ struct ti_sci_reset_control *control;
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+
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+ if (WARN_ON(reset_spec->args_count != rcdev->of_reset_n_cells))
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+ return -EINVAL;
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+
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+ control = devm_kzalloc(data->dev, sizeof(*control), GFP_KERNEL);
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+ if (!control)
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+ return -ENOMEM;
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+
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+ control->dev_id = reset_spec->args[0];
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+ control->reset_mask = reset_spec->args[1];
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+ mutex_init(&control->lock);
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+
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+ return idr_alloc(&data->idr, control, 0, 0, GFP_KERNEL);
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+}
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+
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+static const struct of_device_id ti_sci_reset_of_match[] = {
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+ { .compatible = "ti,sci-reset", },
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+ { /* sentinel */ },
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+};
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+MODULE_DEVICE_TABLE(of, ti_sci_reset_of_match);
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+
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+static int ti_sci_reset_probe(struct platform_device *pdev)
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+{
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+ struct ti_sci_reset_data *data;
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+
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+ if (!pdev->dev.of_node)
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+ return -ENODEV;
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+
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+ data = devm_kzalloc(&pdev->dev, sizeof(*data), GFP_KERNEL);
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+ if (!data)
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+ return -ENOMEM;
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+
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+ data->sci = devm_ti_sci_get_handle(&pdev->dev);
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+ if (IS_ERR(data->sci))
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+ return PTR_ERR(data->sci);
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+
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+ data->rcdev.ops = &ti_sci_reset_ops;
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+ data->rcdev.owner = THIS_MODULE;
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+ data->rcdev.of_node = pdev->dev.of_node;
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+ data->rcdev.of_reset_n_cells = 2;
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+ data->rcdev.of_xlate = ti_sci_reset_of_xlate;
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+ data->dev = &pdev->dev;
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+ idr_init(&data->idr);
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+
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+ platform_set_drvdata(pdev, data);
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+
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+ return reset_controller_register(&data->rcdev);
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+}
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+
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+static int ti_sci_reset_remove(struct platform_device *pdev)
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+{
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+ struct ti_sci_reset_data *data = platform_get_drvdata(pdev);
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+
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+ reset_controller_unregister(&data->rcdev);
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+
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+ idr_destroy(&data->idr);
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+
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+ return 0;
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+}
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+
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+static struct platform_driver ti_sci_reset_driver = {
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+ .probe = ti_sci_reset_probe,
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+ .remove = ti_sci_reset_remove,
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+ .driver = {
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+ .name = "ti-sci-reset",
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+ .of_match_table = ti_sci_reset_of_match,
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+ },
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+};
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+module_platform_driver(ti_sci_reset_driver);
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+
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+MODULE_AUTHOR("Andrew F. Davis <afd@ti.com>");
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+MODULE_DESCRIPTION("TI System Control Interface (TI SCI) Reset driver");
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+MODULE_LICENSE("GPL v2");
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Olof Johansson