[RFC PATCH 1/7] soundwire: Add sysfs support for master(s)

[Pierre-Louis Bossart]

For each master N, add a device sdw-master:N and add the
master properties as attributes.

Credits: this patch is based on an earlier internal contribution by
Vinod Koul, Sanyog Kale, Shreyas Nc and Hardik Shah.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>
---
 drivers/soundwire/Makefile    |   3 +-
 drivers/soundwire/bus.c       |   6 ++
 drivers/soundwire/sysfs.c     | 162 ++++++++++++++++++++++++++++++++++
 include/linux/soundwire/sdw.h |  10 +++
 4 files changed, 180 insertions(+), 1 deletion(-)
 create mode 100644 drivers/soundwire/sysfs.c

diff --git a/drivers/soundwire/Makefile b/drivers/soundwire/Makefile
index 5817beaca0e1..787f1cbf342c 100644
--- a/drivers/soundwire/Makefile
+++ b/drivers/soundwire/Makefile
@@ -3,7 +3,8 @@
 #
 
 #Bus Objs
-soundwire-bus-objs := bus_type.o bus.o slave.o mipi_disco.o stream.o
+soundwire-bus-objs := bus_type.o bus.o slave.o mipi_disco.o stream.o \
+			sysfs.o
 obj-$(CONFIG_SOUNDWIRE_BUS) += soundwire-bus.o
 
 #Cadence Objs
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index fe745830a261..38de7071e135 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -49,6 +49,10 @@ int sdw_add_bus_master(struct sdw_bus *bus)
 		}
 	}
 
+	ret = sdw_sysfs_bus_init(bus);
+	if (ret < 0)
+		dev_warn(bus->dev, "Bus sysfs init failed:%d\n", ret);
+
 	/*
 	 * Device numbers in SoundWire are 0 through 15. Enumeration device
 	 * number (0), Broadcast device number (15), Group numbers (12 and
@@ -129,6 +133,8 @@ static int sdw_delete_slave(struct device *dev, void *data)
  */
 void sdw_delete_bus_master(struct sdw_bus *bus)
 {
+	sdw_sysfs_bus_exit(bus);
+
 	device_for_each_child(bus->dev, NULL, sdw_delete_slave);
 }
 EXPORT_SYMBOL(sdw_delete_bus_master);
diff --git a/drivers/soundwire/sysfs.c b/drivers/soundwire/sysfs.c
new file mode 100644
index 000000000000..7b6c3826a73a
--- /dev/null
+++ b/drivers/soundwire/sysfs.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
+// Copyright(c) 2015-19 Intel Corporation.
+
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/soundwire/sdw.h>
+#include <linux/soundwire/sdw_type.h>
+#include "bus.h"
+
+struct sdw_master_sysfs {
+	struct device dev;
+	struct sdw_bus *bus;
+};
+
+#define to_sdw_device(_dev) \
+	container_of(_dev, struct sdw_master_sysfs, dev)
+
+/*
+ * The sysfs for properties reflects the MIPI description as given
+ * in the MIPI DisCo spec
+ *
+ * Base file is:
+ *	sdw-master-N
+ *      |---- revision
+ *      |---- clk_stop_modes
+ *      |---- max_clk_freq
+ *      |---- clk_freq
+ *      |---- clk_gears
+ *      |---- default_row
+ *      |---- default_col
+ *      |---- dynamic_shape
+ *      |---- err_threshold
+ */
+
+#define sdw_master_attr(field, format_string)				\
+static ssize_t field##_show(struct device *dev,				\
+			    struct device_attribute *attr,		\
+			    char *buf)					\
+{									\
+	struct sdw_master_sysfs *master = to_sdw_device(dev);		\
+	return sprintf(buf, format_string, master->bus->prop.field);	\
+}									\
+static DEVICE_ATTR_RO(field)
+
+sdw_master_attr(revision, "0x%x\n");
+sdw_master_attr(clk_stop_modes, "0x%x\n");
+sdw_master_attr(max_clk_freq, "%d\n");
+sdw_master_attr(default_row, "%d\n");
+sdw_master_attr(default_col, "%d\n");
+sdw_master_attr(default_frame_rate, "%d\n");
+sdw_master_attr(dynamic_frame, "%d\n");
+sdw_master_attr(err_threshold, "%d\n");
+
+static ssize_t clock_frequencies_show(struct device *dev,
+				      struct device_attribute *attr, char *buf)
+{
+	struct sdw_master_sysfs *master = to_sdw_device(dev);
+	ssize_t size = 0;
+	int i;
+
+	for (i = 0; i < master->bus->prop.num_clk_freq; i++)
+		size += sprintf(buf + size, "%8d ",
+				master->bus->prop.clk_freq[i]);
+	size += sprintf(buf + size, "\n");
+
+	return size;
+}
+static DEVICE_ATTR_RO(clock_frequencies);
+
+static ssize_t clock_gears_show(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	struct sdw_master_sysfs *master = to_sdw_device(dev);
+	ssize_t size = 0;
+	int i;
+
+	for (i = 0; i < master->bus->prop.num_clk_gears; i++)
+		size += sprintf(buf + size, "%8d ",
+				master->bus->prop.clk_gears[i]);
+	size += sprintf(buf + size, "\n");
+
+	return size;
+}
+static DEVICE_ATTR_RO(clock_gears);
+
+static struct attribute *master_node_attrs[] = {
+	&dev_attr_revision.attr,
+	&dev_attr_clk_stop_modes.attr,
+	&dev_attr_max_clk_freq.attr,
+	&dev_attr_default_row.attr,
+	&dev_attr_default_col.attr,
+	&dev_attr_default_frame_rate.attr,
+	&dev_attr_dynamic_frame.attr,
+	&dev_attr_err_threshold.attr,
+	&dev_attr_clock_frequencies.attr,
+	&dev_attr_clock_gears.attr,
+	NULL,
+};
+
+static const struct attribute_group sdw_master_node_group = {
+	.attrs = master_node_attrs,
+};
+
+static const struct attribute_group *sdw_master_node_groups[] = {
+	&sdw_master_node_group,
+	NULL
+};
+
+static void sdw_device_release(struct device *dev)
+{
+	struct sdw_master_sysfs *master = to_sdw_device(dev);
+
+	kfree(master);
+}
+
+static struct device_type sdw_device_type = {
+	.name =	"sdw_device",
+	.release = sdw_device_release,
+};
+
+int sdw_sysfs_bus_init(struct sdw_bus *bus)
+{
+	struct sdw_master_sysfs *master;
+	int err;
+
+	if (bus->sysfs) {
+		dev_err(bus->dev, "SDW sysfs is already initialized\n");
+		return -EIO;
+	}
+
+	master = kzalloc(sizeof(*master), GFP_KERNEL);
+	if (!master)
+		return -ENOMEM;
+
+	bus->sysfs = master;
+	master->bus = bus;
+	master->dev.type = &sdw_device_type;
+	master->dev.bus = &sdw_bus_type;
+	master->dev.parent = bus->dev;
+	master->dev.groups = sdw_master_node_groups;
+	dev_set_name(&master->dev, "sdw-master:%x", bus->link_id);
+
+	err = device_register(&master->dev);
+	if (err)
+		put_device(&master->dev);
+
+	return err;
+}
+
+void sdw_sysfs_bus_exit(struct sdw_bus *bus)
+{
+	struct sdw_master_sysfs *master = bus->sysfs;
+
+	if (!master)
+		return;
+
+	master->bus = NULL;
+	put_device(&master->dev);
+	bus->sysfs = NULL;
+}
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index 3b231472464a..b64d46fed0c8 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -402,6 +402,14 @@ int sdw_slave_read_dp0(struct sdw_slave *slave,
 		       struct fwnode_handle *port,
 		       struct sdw_dp0_prop *dp0);
 
+/*
+ * SDW sysfs APIs
+ */
+struct sdw_master_sysfs;
+
+int sdw_sysfs_bus_init(struct sdw_bus *bus);
+void sdw_sysfs_bus_exit(struct sdw_bus *bus);
+
 /*
  * SDW Slave Structures and APIs
  */
@@ -731,6 +739,7 @@ struct sdw_master_ops {
  * @m_rt_list: List of Master instance of all stream(s) running on Bus. This
  * is used to compute and program bus bandwidth, clock, frame shape,
  * transport and port parameters
+ * @sysfs: Bus sysfs
  * @defer_msg: Defer message
  * @clk_stop_timeout: Clock stop timeout computed
  * @bank_switch_timeout: Bank switch timeout computed
@@ -750,6 +759,7 @@ struct sdw_bus {
 	struct sdw_bus_params params;
 	struct sdw_master_prop prop;
 	struct list_head m_rt_list;
+	struct sdw_master_sysfs *sysfs;
 	struct sdw_defer defer_msg;
 	unsigned int clk_stop_timeout;
 	u32 bank_switch_timeout;
-- 
2.17.1