4 files changed, 170 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/clock/pwm-clock.txt b/Documentation/devicetree/bindings/clock/pwm-clock.txt
new file mode 100644
index 000000000000..83db876b3b90
--- /dev/null
+++ b/Documentation/devicetree/bindings/clock/pwm-clock.txt
@@ -0,0 +1,26 @@
+Binding for an external clock signal driven by a PWM pin.
+
+This binding uses the common clock binding[1] and the common PWM binding[2].
+
+[1] Documentation/devicetree/bindings/clock/clock-bindings.txt
+[2] Documentation/devicetree/bindings/pwm/pwm.txt
+
+Required properties:
+- compatible : shall be "pwm-clock".
+- #clock-cells : from common clock binding; shall be set to 0.
+- pwms : from common PWM binding; this determines the clock frequency
+  via the period given in the PWM specifier.
+
+Optional properties:
+- clock-output-names : From common clock binding.
+- clock-frequency : Exact output frequency, in case the PWM period
+  is not exact but was rounded to nanoseconds.
+
+Example:
+        clock {
+                compatible = "pwm-clock";
+                #clock-cells = <0>;
+                clock-frequency = <25000000>;
+                clock-output-names = "mipi_mclk";
+                pwms = <&pwm2 0 40>; /* 1 / 40 ns = 25 MHz */
+        };
diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 0b474a04730f..9897f353bf1a 100644
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -130,6 +130,13 @@ config COMMON_CLK_PALMAS
           This driver supports TI Palmas devices 32KHz output KG and KG_AUDIO
           using common clock framework.
 
+config COMMON_CLK_PWM
+        tristate "Clock driver for PWMs used as clock outputs"
+        depends on PWM
+        ---help---
+          Adapter driver so that any PWM output can be (mis)used as clock signal
+          at 50% duty cycle.
+
 config COMMON_CLK_PXA
         def_bool COMMON_CLK && ARCH_PXA
         ---help---
diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index 1d35f3bb28e0..492bcabe7930 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -43,6 +43,7 @@ obj-$(CONFIG_ARCH_U300)			+= clk-u300.o
 obj-$(CONFIG_ARCH_VT8500)               += clk-vt8500.o
 obj-$(CONFIG_COMMON_CLK_WM831X)         += clk-wm831x.o
 obj-$(CONFIG_COMMON_CLK_XGENE)          += clk-xgene.o
+obj-$(CONFIG_COMMON_CLK_PWM)            += clk-pwm.o
 obj-$(CONFIG_COMMON_CLK_AT91)           += at91/
 obj-$(CONFIG_ARCH_BCM_MOBILE)           += bcm/
 obj-$(CONFIG_ARCH_BERLIN)               += berlin/
diff --git a/drivers/clk/clk-pwm.c b/drivers/clk/clk-pwm.c
new file mode 100644
index 000000000000..328fcfcefd8c
--- /dev/null
+++ b/drivers/clk/clk-pwm.c
@@ -0,0 +1,136 @@
+/*
+ * Copyright (C) 2014 Philipp Zabel, Pengutronix
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * PWM (mis)used as clock output
+ */
+#include <linux/clk-provider.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+struct clk_pwm {
+        struct clk_hw hw;
+        struct pwm_device *pwm;
+        u32 fixed_rate;
+};
+
+static inline struct clk_pwm *to_clk_pwm(struct clk_hw *hw)
+{
+        return container_of(hw, struct clk_pwm, hw);
+}
+
+static int clk_pwm_prepare(struct clk_hw *hw)
+{
+        struct clk_pwm *clk_pwm = to_clk_pwm(hw);
+
+        return pwm_enable(clk_pwm->pwm);
+}
+
+static void clk_pwm_unprepare(struct clk_hw *hw)
+{
+        struct clk_pwm *clk_pwm = to_clk_pwm(hw);
+
+        pwm_disable(clk_pwm->pwm);
+}
+
+static unsigned long clk_pwm_recalc_rate(struct clk_hw *hw,
+                                         unsigned long parent_rate)
+{
+        struct clk_pwm *clk_pwm = to_clk_pwm(hw);
+
+        return clk_pwm->fixed_rate;
+}
+
+static const struct clk_ops clk_pwm_ops = {
+        .prepare = clk_pwm_prepare,
+        .unprepare = clk_pwm_unprepare,
+        .recalc_rate = clk_pwm_recalc_rate,
+};
+
+static int clk_pwm_probe(struct platform_device *pdev)
+{
+        struct device_node *node = pdev->dev.of_node;
+        struct clk_init_data init;
+        struct clk_pwm *clk_pwm;
+        struct pwm_device *pwm;
+        const char *clk_name;
+        struct clk *clk;
+        int ret;
+
+        clk_pwm = devm_kzalloc(&pdev->dev, sizeof(*clk_pwm), GFP_KERNEL);
+        if (!clk_pwm)
+                return -ENOMEM;
+
+        pwm = devm_pwm_get(&pdev->dev, NULL);
+        if (IS_ERR(pwm))
+                return PTR_ERR(pwm);
+
+        if (!pwm->period) {
+                dev_err(&pdev->dev, "invalid PWM period\n");
+                return -EINVAL;
+        }
+
+        if (of_property_read_u32(node, "clock-frequency", &clk_pwm->fixed_rate))
+                clk_pwm->fixed_rate = NSEC_PER_SEC / pwm->period;
+
+        if (pwm->period != NSEC_PER_SEC / clk_pwm->fixed_rate &&
+            pwm->period != DIV_ROUND_UP(NSEC_PER_SEC, clk_pwm->fixed_rate)) {
+                dev_err(&pdev->dev,
+                        "clock-frequency does not match PWM period\n");
+                return -EINVAL;
+        }
+
+        ret = pwm_config(pwm, (pwm->period + 1) >> 1, pwm->period);
+        if (ret < 0)
+                return ret;
+
+        clk_name = node->name;
+        of_property_read_string(node, "clock-output-names", &clk_name);
+
+        init.name = clk_name;
+        init.ops = &clk_pwm_ops;
+        init.flags = CLK_IS_BASIC | CLK_IS_ROOT;
+        init.num_parents = 0;
+
+        clk_pwm->pwm = pwm;
+        clk_pwm->hw.init = &init;
+        clk = devm_clk_register(&pdev->dev, &clk_pwm->hw);
+        if (IS_ERR(clk))
+                return PTR_ERR(clk);
+
+        return of_clk_add_provider(node, of_clk_src_simple_get, clk);
+}
+
+static int clk_pwm_remove(struct platform_device *pdev)
+{
+        of_clk_del_provider(pdev->dev.of_node);
+
+        return 0;
+}
+
+static const struct of_device_id clk_pwm_dt_ids[] = {
+        { .compatible = "pwm-clock" },
+        { }
+};
+MODULE_DEVICE_TABLE(of, clk_pwm_dt_ids);
+
+static struct platform_driver clk_pwm_driver = {
+        .probe = clk_pwm_probe,
+        .remove = clk_pwm_remove,
+        .driver = {
+                .name = "pwm-clock",
+                .of_match_table = of_match_ptr(clk_pwm_dt_ids),
+        },
+};
+
+module_platform_driver(clk_pwm_driver);
+
+MODULE_AUTHOR("Philipp Zabel <p.zabel@pengutronix.de>");
+MODULE_DESCRIPTION("PWM clock driver");
+MODULE_LICENSE("GPL");