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authorStephen Warren <swarren@nvidia.com>2016-06-17 09:43:58 -0600
committerSimon Glass <sjg@chromium.org>2016-06-19 17:05:55 -0600
commit89c1e2da78f82a09685006291ce8bb44f635fa25 (patch)
tree4962e19a65e7cf8caf997ee92ec16030dead512a /include/reset.h
parent0f67e2395be44db2c1bef17b6ada2e46221908ed (diff)
Add a reset driver framework/uclass
A reset controller is a hardware module that controls reset signals that affect other hardware modules or chips. This patch defines a standard API that connects reset clients (i.e. the drivers for devices affected by reset signals) to drivers for reset controllers/providers. Initially, DT is the only supported method for connecting the two. The DT binding specification (reset.txt) was taken from Linux kernel v4.5's Documentation/devicetree/bindings/reset/reset.txt. Signed-off-by: Stephen Warren <swarren@nvidia.com> Acked-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'include/reset.h')
-rw-r--r--include/reset.h135
1 files changed, 135 insertions, 0 deletions
diff --git a/include/reset.h b/include/reset.h
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+/*
+ * Copyright (c) 2016, NVIDIA CORPORATION.
+ *
+ * SPDX-License-Identifier: GPL-2.0
+ */
+
+#ifndef _RESET_H
+#define _RESET_H
+
+/**
+ * A reset is a hardware signal indicating that a HW module (or IP block, or
+ * sometimes an entire off-CPU chip) reset all of its internal state to some
+ * known-good initial state. Drivers will often reset HW modules when they
+ * begin execution to ensure that hardware correctly responds to all requests,
+ * or in response to some error condition. Reset signals are often controlled
+ * externally to the HW module being reset, by an entity this API calls a reset
+ * controller. This API provides a standard means for drivers to request that
+ * reset controllers set or clear reset signals.
+ *
+ * A driver that implements UCLASS_RESET is a reset controller or provider. A
+ * controller will often implement multiple separate reset signals, since the
+ * hardware it manages often has this capability. reset-uclass.h describes the
+ * interface which reset controllers must implement.
+ *
+ * Reset consumers/clients are the HW modules affected by reset signals. This
+ * header file describes the API used by drivers for those HW modules.
+ */
+
+struct udevice;
+
+/**
+ * struct reset_ctl - A handle to (allowing control of) a single reset signal.
+ *
+ * Clients provide storage for reset control handles. The content of the
+ * structure is managed solely by the reset API and reset drivers. A reset
+ * control struct is initialized by "get"ing the reset control struct. The
+ * reset control struct is passed to all other reset APIs to identify which
+ * reset signal to operate upon.
+ *
+ * @dev: The device which implements the reset signal.
+ * @id: The reset signal ID within the provider.
+ *
+ * Currently, the reset API assumes that a single integer ID is enough to
+ * identify and configure any reset signal for any reset provider. If this
+ * assumption becomes invalid in the future, the struct could be expanded to
+ * either (a) add more fields to allow reset providers to store additional
+ * information, or (b) replace the id field with an opaque pointer, which the
+ * provider would dynamically allocated during its .of_xlate op, and process
+ * during is .request op. This may require the addition of an extra op to clean
+ * up the allocation.
+ */
+struct reset_ctl {
+ struct udevice *dev;
+ /*
+ * Written by of_xlate. We assume a single id is enough for now. In the
+ * future, we might add more fields here.
+ */
+ unsigned long id;
+};
+
+/**
+ * reset_get_by_index - Get/request a reset signal by integer index.
+ *
+ * This looks up and requests a reset signal. The index is relative to the
+ * client device; each device is assumed to have n reset signals associated
+ * with it somehow, and this function finds and requests one of them. The
+ * mapping of client device reset signal indices to provider reset signals may
+ * be via device-tree properties, board-provided mapping tables, or some other
+ * mechanism.
+ *
+ * @dev: The client device.
+ * @index: The index of the reset signal to request, within the client's
+ * list of reset signals.
+ * @reset_ctl A pointer to a reset control struct to initialize.
+ * @return 0 if OK, or a negative error code.
+ */
+int reset_get_by_index(struct udevice *dev, int index,
+ struct reset_ctl *reset_ctl);
+
+/**
+ * reset_get_by_name - Get/request a reset signal by name.
+ *
+ * This looks up and requests a reset signal. The name is relative to the
+ * client device; each device is assumed to have n reset signals associated
+ * with it somehow, and this function finds and requests one of them. The
+ * mapping of client device reset signal names to provider reset signal may be
+ * via device-tree properties, board-provided mapping tables, or some other
+ * mechanism.
+ *
+ * @dev: The client device.
+ * @name: The name of the reset signal to request, within the client's
+ * list of reset signals.
+ * @reset_ctl: A pointer to a reset control struct to initialize.
+ * @return 0 if OK, or a negative error code.
+ */
+int reset_get_by_name(struct udevice *dev, const char *name,
+ struct reset_ctl *reset_ctl);
+
+/**
+ * reset_free - Free a previously requested reset signal.
+ *
+ * @reset_ctl: A reset control struct that was previously successfully
+ * requested by reset_get_by_*().
+ * @return 0 if OK, or a negative error code.
+ */
+int reset_free(struct reset_ctl *reset_ctl);
+
+/**
+ * reset_assert - Assert a reset signal.
+ *
+ * This function will assert the specified reset signal, thus resetting the
+ * affected HW module(s). Depending on the reset controller hardware, the reset
+ * signal will either stay asserted until reset_deassert() is called, or the
+ * hardware may autonomously clear the reset signal itself.
+ *
+ * @reset_ctl: A reset control struct that was previously successfully
+ * requested by reset_get_by_*().
+ * @return 0 if OK, or a negative error code.
+ */
+int reset_assert(struct reset_ctl *reset_ctl);
+
+/**
+ * reset_deassert - Deassert a reset signal.
+ *
+ * This function will deassert the specified reset signal, thus releasing the
+ * affected HW modules() from reset, and allowing them to continue normal
+ * operation.
+ *
+ * @reset_ctl: A reset control struct that was previously successfully
+ * requested by reset_get_by_*().
+ * @return 0 if OK, or a negative error code.
+ */
+int reset_deassert(struct reset_ctl *reset_ctl);
+
+#endif