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Message-ID: <518D320C.4010707@elopez.com.ar>
Date: Fri, 10 May 2013 14:44:44 -0300
From: Emilio López <emilio@...pez.com.ar>
To: Soren Brinkmann <soren.brinkmann@...inx.com>
CC: Mike Turquette <mturquette@...aro.org>,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH RFC] clk: Introduce userspace clock driver
Hi,
El 10/05/13 14:31, Soren Brinkmann escribió:
> 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@...inx.com>
> ---
> .../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>;
> + };
Does this belong on DT? It isn't describing hardware, is it?
> 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
> + *
> + * Sören Brinkmann <soren.brinkmann@...inx.com>
> + *
> + * 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
> +};
For debugging purposes, being able to change parents would be nice too.
Maybe this belongs to debugfs instead of sysfs though.
> +
> +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);
>
--
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