[PATCH RFC] clk: Introduce userspace clock driver
From: Soren Brinkmann
Date: Fri May 10 2013 - 13:32:09 EST
The userspace clock driver can be used to expose clock controls through
sysfs to userspace. The driver creates entries in /sys/class/clk.
Signed-off-by: Soren Brinkmann <soren.brinkmann@xxxxxxxxxx>
---
.../devicetree/bindings/clock/clk-userspace.txt | 7 +
drivers/clk/Kconfig | 9 ++
drivers/clk/Makefile | 1 +
drivers/clk/clk-userspace.c | 169 +++++++++++++++++++++
4 files changed, 186 insertions(+)
create mode 100644 Documentation/devicetree/bindings/clock/clk-userspace.txt
create mode 100644 drivers/clk/clk-userspace.c
diff --git a/Documentation/devicetree/bindings/clock/clk-userspace.txt b/Documentation/devicetree/bindings/clock/clk-userspace.txt
new file mode 100644
index 0000000..2d153c7
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/clk-userspace.txt
@@ -0,0 +1,7 @@
+
+Example:
+ usclk: usclk {
+ compatible = "clk-userspace";
+ clocks = <&foo 15>, <&bar>;
+ clock-count = <2>;
+ };
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 0357ac4..b35b62c 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -81,6 +81,15 @@ config COMMON_CLK_AXI_CLKGEN
Support for the Analog Devices axi-clkgen pcore clock generator for Xilinx
FPGAs. It is commonly used in Analog Devices' reference designs.
+config COMMON_CLK_USERSPACE
+ bool "Userspace Clock Controls"
+ depends on OF
+ depends on SYSFS
+ help
+ ---help---
+ Expose clock controls through sysfs to userspace. Clocks are selected
+ through the device tree and the controls are exposed in
+ /sys/class/clk.
endmenu
source "drivers/clk/mvebu/Kconfig"
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index fa435bc..f2f68c8 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-fixed-rate.o
obj-$(CONFIG_COMMON_CLK) += clk-gate.o
obj-$(CONFIG_COMMON_CLK) += clk-mux.o
obj-$(CONFIG_COMMON_CLK) += clk-composite.o
+obj-$(CONFIG_COMMON_CLK_USERSPACE) += clk-userspace.o
# SoCs specific
obj-$(CONFIG_ARCH_BCM2835) += clk-bcm2835.o
diff --git a/drivers/clk/clk-userspace.c b/drivers/clk/clk-userspace.c
new file mode 100644
index 0000000..931cf92
--- /dev/null
+++ b/drivers/clk/clk-userspace.c
@@ -0,0 +1,169 @@
+/*
+ * Userspace clock driver
+ *
+ * Copyright (C) 2013 Xilinx
+ *
+ * SÃren Brinkmann <soren.brinkmann@xxxxxxxxxx>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Expose clock controls through sysfs to userspace.
+ *
+ * By writing 0/1 to 'enable' the clock can be disabled/enabled. Reading
+ * that file returns the current state - 0 = disabled, 1 = enabled.
+ *
+ * Reading 'set_rate' returns the current clock frequency in Hz. Writing
+ * the file requests setting a new frequency in Hz.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+
+#define DRIVER_NAME "clk-userspace"
+
+struct usclk_data {
+ struct clk *clk;
+ int enabled;
+};
+
+static ssize_t enable_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct usclk_data *pdata = dev_get_drvdata(dev);
+
+ return scnprintf(buf, PAGE_SIZE, "%u\n", pdata->enabled);
+}
+
+static ssize_t enable_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ unsigned long enable;
+ int ret;
+ struct usclk_data *pdata = dev_get_drvdata(dev);
+
+ ret = kstrtoul(buf, 0, &enable);
+ if (ret)
+ return -EINVAL;
+
+ enable = !!enable;
+ if (enable == pdata->enabled)
+ return count;
+
+ if (enable)
+ ret = clk_prepare_enable(pdata->clk);
+ else
+ clk_disable_unprepare(pdata->clk);
+
+ if (ret)
+ return -EBUSY;
+
+ pdata->enabled = enable;
+ return count;
+}
+
+static DEVICE_ATTR(enable, 0644, enable_show, enable_store);
+
+static ssize_t set_rate_show(struct device *dev, struct device_attribute *attr,
+ char *buf)
+{
+ struct usclk_data *pdata = dev_get_drvdata(dev);
+
+ return scnprintf(buf, PAGE_SIZE, "%lu\n", clk_get_rate(pdata->clk));
+}
+
+static ssize_t set_rate_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret = 0;
+ unsigned long rate;
+ struct usclk_data *pdata = dev_get_drvdata(dev);
+
+ ret = kstrtoul(buf, 0, &rate);
+ if (ret)
+ return -EINVAL;
+
+ rate = clk_round_rate(pdata->clk, rate);
+ ret = clk_set_rate(pdata->clk, rate);
+ if (ret)
+ return -EBUSY;
+
+ return count;
+}
+
+static DEVICE_ATTR(set_rate, 0644, set_rate_show, set_rate_store);
+
+static const struct attribute *usclk_attrs[] = {
+ &dev_attr_enable.attr,
+ &dev_attr_set_rate.attr,
+ NULL
+};
+
+static const struct attribute_group usclk_attr_grp = {
+ .attrs = (struct attribute **)usclk_attrs,
+};
+
+static int usclk_setup(void)
+{
+ int ret;
+ int i;
+ struct usclk_data *pdata;
+ u32 clock_count;
+ struct class *clk_class;
+ struct device *dev;
+ struct device_node *np = of_find_compatible_node(NULL, NULL,
+ "clk-userspace");
+
+ ret = of_property_read_u32(np, "clock-count", &clock_count);
+ if (ret || !clock_count)
+ return ret;
+
+ pdata = kzalloc(clock_count * sizeof(*pdata), GFP_KERNEL);
+ if (!pdata)
+ return -ENOMEM;
+
+ clk_class = class_create(THIS_MODULE, "clk");
+ if (!clk_class) {
+ pr_err("unable to create class\n");
+ goto err_free;
+ }
+
+ for (i = 0; i < clock_count; i++) {
+ pdata[i].clk = of_clk_get(np, i);
+ if (IS_ERR(pdata[i].clk)) {
+ pr_warn("input clock #%u not found\n", i);
+ continue;
+ }
+
+ dev = device_create(clk_class, NULL, MKDEV(0, 0), NULL,
+ of_clk_get_parent_name(np, i));
+ if (!dev) {
+ pr_warn("unable to create device #%d\n", i);
+ continue;
+ }
+
+ dev_set_drvdata(dev, &pdata[i]);
+ sysfs_create_group(&dev->kobj, &usclk_attr_grp);
+ }
+
+ return 0;
+
+err_free:
+ kfree(pdata);
+
+ return ret;
+}
+late_initcall(usclk_setup);
--
1.8.2.3
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