Like I2C busses SPI devices can also sit behind multiplexers.
This patch adds is based off the I2C implementation and allows
description in the devicetree.
Signed-off-by: Ben Whitten <ben.whit...@gmail.com>
---
drivers/spi/Kconfig | 10 +++
drivers/spi/Makefile | 3 +
drivers/spi/spi-mux.c | 181 ++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/spi-mux.h | 55 +++++++++++++++
4 files changed, 249 insertions(+)
create mode 100644 drivers/spi/spi-mux.c
create mode 100644 include/linux/spi-mux.h
diff --git a/drivers/spi/Kconfig b/drivers/spi/Kconfig
index a75f2a2..58eba70 100644
--- a/drivers/spi/Kconfig
+++ b/drivers/spi/Kconfig
@@ -51,6 +51,16 @@ config SPI_MASTER
if SPI_MASTER
+config SPI_MUX
+ tristate "SPI bus multiplexing support"
+ help
+ Say Y here if you want the SPI core to support the ability to
+ handle multiplexed SPI bus topologies, by presenting each
+ multiplexed segment as an SPI controller.
+
+ This support is also available as a module. If so, the module
+ will be called spi-mux.
+
comment "SPI Master Controller Drivers"
config SPI_ALTERA
diff --git a/drivers/spi/Makefile b/drivers/spi/Makefile
index 8e0cda7..ef525fe 100644
--- a/drivers/spi/Makefile
+++ b/drivers/spi/Makefile
@@ -109,6 +109,9 @@ obj-$(CONFIG_SPI_XLP) += spi-xlp.o
obj-$(CONFIG_SPI_XTENSA_XTFPGA) += spi-xtensa-xtfpga.o
obj-$(CONFIG_SPI_ZYNQMP_GQSPI) += spi-zynqmp-gqspi.o
+# SPI muxs
+obj-$(CONFIG_SPI_MUX) += spi-mux.o
+
# SPI slave protocol handlers
obj-$(CONFIG_SPI_SLAVE_TIME) += spi-slave-time.o
obj-$(CONFIG_SPI_SLAVE_SYSTEM_CONTROL) += spi-slave-system-control.o
diff --git a/drivers/spi/spi-mux.c b/drivers/spi/spi-mux.c
new file mode 100644
index 0000000..a2008c1
--- /dev/null
+++ b/drivers/spi/spi-mux.c
@@ -0,0 +1,181 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for an SPI multiplexer
+ *
+ * Copyright (c) 2018 Ben Whitten
+ */
+
+#include <linux/spi/spi.h>
+#include <linux/spi-mux.h>
+#include <linux/of.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+struct spi_mux_priv {
+ struct spi_controller *controller;
+ struct spi_mux_core *muxc;
+ u32 chan_id;
+};
+
+struct spi_mux_core *spi_mux_alloc(struct spi_controller *parent,
+ struct device *dev,
+ int max_controllers,
+ int sizeof_priv,
+ int (*select)(struct spi_mux_core *, u32),
+ int (*deselect)(struct spi_mux_core *, u32),
+ int (*transfer_one_message)
+ (struct spi_controller *controller,
+ struct spi_message *msg))
+{
+ struct spi_mux_core *muxc;
+
+ muxc = devm_kzalloc(dev, sizeof(*muxc)
+ + max_controllers * sizeof(muxc->controller[0])
+ + sizeof_priv, GFP_KERNEL);
+ if (!muxc)
+ return NULL;
+ if (sizeof_priv)
+ muxc->priv = &muxc->controller[max_controllers];
+
+ muxc->parent = parent;
+ muxc->dev = dev;
+
+ muxc->select = select;
+ muxc->deselect = deselect;
+ muxc->transfer_one_message = transfer_one_message;
+ muxc->max_controllers = max_controllers;
+
+ return muxc;
+}
+EXPORT_SYMBOL_GPL(spi_mux_alloc);
+
+u32 spi_mux_get_chan_id(struct spi_controller *controller)
+{
+ struct spi_mux_priv *priv = spi_controller_get_devdata(controller);
+
+ return priv->chan_id;
+}
+EXPORT_SYMBOL_GPL(spi_mux_get_chan_id);
+
+static int spi_mux_transfer_one_message(struct spi_controller *controller,
+ struct spi_message *msg)
+{
+ struct spi_mux_priv *priv = spi_controller_get_devdata(controller);
+ struct spi_mux_core *muxc = priv->muxc;
+ struct spi_device *spi = to_spi_device(muxc->dev);
+ int ret;
+
+ ret = muxc->select(muxc, priv->chan_id);
+ if (ret < 0)
+ return ret;
+
+ /* If we have a custom transfer, use it */
+ if (muxc->transfer_one_message)
+ ret = muxc->transfer_one_message(controller, msg);
+ else
+ ret = spi_sync(spi, msg);
+
+ if (muxc->deselect)
+ muxc->deselect(muxc, priv->chan_id);
+
+ return ret;
+}
+
+static int spi_mux_add_controller(struct spi_mux_core *muxc, u32 chan_id)
+{
+ struct spi_controller *controller;
+ struct spi_mux_priv *priv;
+ int ret;
+
+ if (muxc->num_controllers >= muxc->max_controllers) {
+ dev_err(muxc->dev, "No room for more spi-mux controllers");
+ return -EINVAL;
+ }
+
+ controller = spi_alloc_master(muxc->dev, sizeof(*priv));
+ if (!controller)
+ return -ENOMEM;
+ priv = spi_controller_get_devdata(controller);
+
+ /* Setup private controller data */
+ priv->muxc = muxc;
+ priv->controller = controller;
+ priv->chan_id = chan_id;
+
+ priv->controller->transfer_one_message = spi_mux_transfer_one_message;
+
+ /* Look for the child of this controller */
+ if (muxc->dev->of_node) {
+ struct device_node *dev_node = muxc->dev->of_node;
+ struct device_node *mux_node, *child = NULL;
+ u32 reg;
+
+ mux_node = of_get_child_by_name(dev_node, "spi-mux");
+ if (!mux_node)
+ mux_node = of_node_get(dev_node);
+
+ for_each_child_of_node(mux_node, child) {
+ ret = of_property_read_u32(child, "reg", ®);
+ if (ret)
+ continue;
+ if (chan_id == reg)
+ break;
+ }
+
+ priv->controller->dev.of_node = child;
+ of_node_put(mux_node);
+ }
+
+ ret = devm_spi_register_controller(muxc->dev, priv->controller);
+ if (ret) {
+ spi_controller_put(priv->controller);
+ dev_err(muxc->dev, "Problem registering spi controller: %d\n",
+ ret);
+ return ret;
+ }
+
+ muxc->controller[muxc->num_controllers++] = priv->controller;
+
+ return ret;
+}
+
+static void spi_mux_del_controllers(struct spi_mux_core *muxc)
+{
+ struct spi_controller *controller =
+ muxc->controller[--muxc->num_controllers];
+ struct device_node *np = controller->dev.of_node;
+
+ muxc->controller[muxc->num_controllers] = NULL;
+ of_node_put(np);
+}
+
+static void devm_spi_mux_del_controllers(struct device *dev, void *res)
+{
+ spi_mux_del_controllers(*(struct spi_mux_core **)res);
+}
+
+int devm_spi_mux_add_controller(struct spi_mux_core *muxc, u32 chan_id)
+{
+ struct spi_mux_core **ptr;
+ int ret;
+
+ ptr = devres_alloc(devm_spi_mux_del_controllers, sizeof(*ptr),
+ GFP_KERNEL);
+ if (!ptr)
+ return -ENOMEM;
+
+ ret = spi_mux_add_controller(muxc, chan_id);
+ if (!ret) {
+ *ptr = muxc;
+ devres_add(muxc->dev, ptr);
+ } else {
+ devres_free(ptr);
+ }
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(devm_spi_mux_add_controller);
+
+MODULE_AUTHOR("Ben Whitten <ben.whit...@gmail.com>");
+MODULE_DESCRIPTION("SPI driver for multiplexed SPI busses");
+MODULE_LICENSE("GPL v2");
diff --git a/include/linux/spi-mux.h b/include/linux/spi-mux.h
new file mode 100644
index 0000000..5978f86
--- /dev/null
+++ b/include/linux/spi-mux.h
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for an SPI multiplexer
+ *
+ * Copyright (c) 2018 Ben Whitten
+ */
+
+#ifndef _LINUX_SPI_MUX_H_
+#define _LINUX_SPI_MUX_H_
+
+#ifdef __KERNEL__
+
+struct spi_mux_core {
+ struct spi_controller *parent;
+ struct device *dev;
+
+ void *priv;
+
+ int (*select)(struct spi_mux_core *, u32 chan_id);
+ int (*deselect)(struct spi_mux_core *, u32 chan_id);
+ int (*transfer_one_message)(struct spi_controller *controller,
+ struct spi_message *msg);
+
+ int num_controllers;
+ int max_controllers;
+ struct spi_controller *controller[0];
+};
+
+struct spi_mux_core *spi_mux_alloc(struct spi_controller *parent,
+ struct device *dev,
+ int max_controllers,
+ int sizeof_priv,
+ int (*select)(struct spi_mux_core *, u32),
+ int (*deselect)(struct spi_mux_core *, u32),
+ int (*transfer_one_message)
+ (struct spi_controller *controller,
+ struct spi_message *msg));
+
+static inline void *spi_mux_priv(struct spi_mux_core *muxc)
+{
+ return muxc->priv;
+}
+
+u32 spi_mux_get_chan_id(struct spi_controller *controller);
+
+/*
+ * Called to create an spi bus on a multiplexed bus segment.
+ * The chan_id parameter is passed to the select and deselect
+ * callback functions to perform hardware-specific mux control.
+ */
+int devm_spi_mux_add_controller(struct spi_mux_core *muxc, u32 chan_id);
+
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_SPI_MUX_H_ */
--
2.7.4
