Adds an interface for slave device multiplexing, and an implementation
for GPIO-based multiplexers.
Signed-off-by: Ulrich Hecht <ulrich.hecht+renesas@xxxxxxxxx>
---
drivers/tty/serdev/Kconfig | 3 ++
drivers/tty/serdev/Makefile | 1 +
drivers/tty/serdev/core.c | 43 ++++++++++++++++++++++-
drivers/tty/serdev/mux-gpio.c | 80 +++++++++++++++++++++++++++++++++++++++++++
include/linux/serdev.h | 26 ++++++++++++--
5 files changed, 149 insertions(+), 4 deletions(-)
create mode 100644 drivers/tty/serdev/mux-gpio.c
diff --git a/drivers/tty/serdev/Kconfig b/drivers/tty/serdev/Kconfig
index cdc6b82..7946eeb 100644
--- a/drivers/tty/serdev/Kconfig
+++ b/drivers/tty/serdev/Kconfig
@@ -13,4 +13,7 @@ config SERIAL_DEV_CTRL_TTYPORT
depends on TTY
depends on SERIAL_DEV_BUS != m
+config SERIAL_DEV_MUX_GPIO
+ bool "Serial device GPIO multiplexer"
+
endif
diff --git a/drivers/tty/serdev/Makefile b/drivers/tty/serdev/Makefile
index 0cbdb94..08a90fa 100644
--- a/drivers/tty/serdev/Makefile
+++ b/drivers/tty/serdev/Makefile
@@ -1,5 +1,6 @@
serdev-objs := core.o
obj-$(CONFIG_SERIAL_DEV_BUS) += serdev.o
+obj-$(CONFIG_SERIAL_DEV_MUX_GPIO) += mux-gpio.o
obj-$(CONFIG_SERIAL_DEV_CTRL_TTYPORT) += serdev-ttyport.o
diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
index 1fbaa4c..9a2c76b 100644
--- a/drivers/tty/serdev/core.c
+++ b/drivers/tty/serdev/core.c
@@ -305,7 +305,8 @@ struct serdev_device *serdev_device_alloc(struct serdev_controller *ctrl)
return NULL;
serdev->ctrl = ctrl;
- ctrl->serdev = serdev;
+ if (!ctrl->serdev)
+ ctrl->serdev = serdev;
device_initialize(&serdev->dev);
serdev->dev.parent = &ctrl->dev;
serdev->dev.bus = &serdev_bus_type;
@@ -368,6 +369,8 @@ static int of_serdev_register_devices(struct serdev_controller *ctrl)
struct serdev_device *serdev = NULL;
int err;
bool found = false;
+ int nr = 0;
+ u32 reg;
for_each_available_child_of_node(ctrl->dev.of_node, node) {
if (!of_get_property(node, "compatible", NULL))
@@ -380,6 +383,10 @@ static int of_serdev_register_devices(struct serdev_controller *ctrl)
continue;
serdev->dev.of_node = node;
+ serdev->nr = nr++;
+
+ if (!of_property_read_u32(node, "reg", ®))
+ serdev->mux_addr = reg;
err = serdev_device_add(serdev);
if (err) {
@@ -395,6 +402,36 @@ static int of_serdev_register_devices(struct serdev_controller *ctrl)
return 0;
}
+int serdev_device_mux_select(struct serdev_device *serdev)
+{
+ struct serdev_mux *mux = serdev->ctrl->mux;
+
+ if (!mux || !mux->ops || !mux->ops->select)
+ return -EINVAL;
+
+ rt_mutex_lock(&mux->mux_lock);
+
+ mux->ops->select(serdev);
+ serdev->ctrl->serdev = serdev;
+
+ return 0;
+}
+
+int serdev_device_mux_deselect(struct serdev_device *serdev)
+{
+ struct serdev_mux *mux = serdev->ctrl->mux;
+
+ if (!mux || serdev->ctrl->serdev != serdev)
+ return -EINVAL;
+
+ if (mux->ops->deselect)
+ mux->ops->deselect(serdev);
+
+ rt_mutex_unlock(&mux->mux_lock);
+
+ return 0;
+}
+
/**
* serdev_controller_add() - Add an serdev controller
* @ctrl: controller to be registered.
@@ -414,6 +451,10 @@ int serdev_controller_add(struct serdev_controller *ctrl)
if (ret)
return ret;
+#ifdef CONFIG_SERIAL_DEV_MUX_GPIO
+ of_serdev_register_gpio_mux(ctrl);
+#endif
+
ret = of_serdev_register_devices(ctrl);
if (ret)
goto out_dev_del;
diff --git a/drivers/tty/serdev/mux-gpio.c b/drivers/tty/serdev/mux-gpio.c
new file mode 100644
index 0000000..5bedff1
--- /dev/null
+++ b/drivers/tty/serdev/mux-gpio.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (C) 2017 Ulrich Hecht
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/of_gpio.h>
+#include <linux/serdev.h>
+#include <linux/slab.h>
+
+static int serdev_device_mux_select_gpio(struct serdev_device *serdev)
+{
+ int i;
+ u32 addr;
+ struct serdev_mux *mux = serdev->ctrl->mux;
+
+ addr = serdev->mux_addr;
+ for (i = 0; i < mux->ngpios; ++i, addr >>= 1) {
+ gpio_request_one(mux->gpios[i], GPIOF_DIR_OUT |
+ (addr & 1) ? GPIOF_INIT_HIGH : GPIOF_INIT_LOW,
+ "mux-enable-gpio");
+ }
+
+ return 0;
+}
+
+static int serdev_device_mux_deselect_gpio(struct serdev_device *serdev)
+{
+ int i;
+ struct serdev_mux *mux = serdev->ctrl->mux;
+
+ for (i = 0; i < mux->ngpios; ++i)
+ gpio_free(mux->gpios[i]);
+
+ return 0;
+}
+
+static const struct serdev_mux_ops gpio_mux_ops = {
+ .select = serdev_device_mux_select_gpio,
+ .deselect = serdev_device_mux_deselect_gpio,
+};
+
+int of_serdev_register_gpio_mux(struct serdev_controller *ctrl)
+{
+ int i, ngpios;
+ struct serdev_mux *mux;
+ struct device_node *np = ctrl->dev.of_node;
+
+ ngpios = of_gpio_named_count(np, "mux-select-gpios");
+ if (ngpios <= 0)
+ return -ENODEV;
+
+ mux = kzalloc(sizeof(*mux), GFP_KERNEL);
+ if (!mux)
+ return -ENOMEM;
+
+ rt_mutex_init(&mux->mux_lock);
+ mux->ops = &gpio_mux_ops;
+
+ mux->ngpios = ngpios;
+
+ mux->gpios = kcalloc(ngpios, sizeof(int), GFP_KERNEL);
+ if (!mux->gpios)
+ return -ENOMEM;
+
+ for (i = 0; i < ngpios; ++i)
+ mux->gpios[i] = of_get_named_gpio(np, "mux-select-gpios", i);
+
+ ctrl->mux = mux;
+
+ return 0;
+}
+
diff --git a/include/linux/serdev.h b/include/linux/serdev.h
index 8b67fcd..e86a0ad 100644
--- a/include/linux/serdev.h
+++ b/include/linux/serdev.h
@@ -17,6 +17,7 @@
#include <linux/device.h>
#include <linux/termios.h>
#include <linux/delay.h>
+#include <linux/rtmutex.h>
struct serdev_controller;
struct serdev_device;
@@ -51,6 +52,7 @@ struct serdev_device {
const struct serdev_device_ops *ops;
struct completion write_comp;
struct mutex write_lock;
+ int mux_addr;
};
static inline struct serdev_device *to_serdev_device(struct device *d)
@@ -76,6 +78,20 @@ static inline struct serdev_device_driver *to_serdev_device_driver(struct device
return container_of(d, struct serdev_device_driver, driver);
}
+struct serdev_mux_ops {
+ int (*select)(struct serdev_device *);
+ int (*deselect)(struct serdev_device *);
+};
+
+struct serdev_mux {
+ int ngpios;
+ int *gpios;
+ struct rt_mutex mux_lock;
+ const struct serdev_mux_ops *ops;
+};
+
+int of_serdev_register_gpio_mux(struct serdev_controller *ctrl);
+
/*
* serdev controller structures
*/
@@ -97,14 +113,16 @@ struct serdev_controller_ops {
* struct serdev_controller - interface to the serdev controller
* @dev: Driver model representation of the device.
* @nr: number identifier for this controller/bus.
- * @serdev: Pointer to slave device for this controller.
+ * @serdev: Pointer to active slave device for this controller.
* @ops: Controller operations.
+ * @mux: Slave multiplexer.
*/
struct serdev_controller {
struct device dev;
unsigned int nr;
struct serdev_device *serdev;
const struct serdev_controller_ops *ops;
+ struct serdev_mux *mux;
};
static inline struct serdev_controller *to_serdev_controller(struct device *d)
@@ -172,7 +190,7 @@ static inline void serdev_controller_write_wakeup(struct serdev_controller *ctrl
{
struct serdev_device *serdev = ctrl->serdev;
- if (!serdev || !serdev->ops->write_wakeup)
+ if (!serdev || !serdev->ops || !serdev->ops->write_wakeup)
return;
serdev->ops->write_wakeup(serdev);
@@ -184,7 +202,7 @@ static inline int serdev_controller_receive_buf(struct serdev_controller *ctrl,
{
struct serdev_device *serdev = ctrl->serdev;
- if (!serdev || !serdev->ops->receive_buf)
+ if (!serdev || !serdev->ops || !serdev->ops->receive_buf)
return -EINVAL;
return serdev->ops->receive_buf(serdev, data, count);
@@ -204,6 +222,8 @@ void serdev_device_write_wakeup(struct serdev_device *);
int serdev_device_write(struct serdev_device *, const unsigned char *, size_t, unsigned long);
void serdev_device_write_flush(struct serdev_device *);
int serdev_device_write_room(struct serdev_device *);
+int serdev_device_mux_select(struct serdev_device *);
+int serdev_device_mux_deselect(struct serdev_device *);
/*
* serdev device driver functions
--
2.7.4
