pwm: Add new pwm-samsung driver

This patch introduces new Samsung PWM driver, which is completely
rewritten to be multiplatform- and DeviceTree-aware.

In addition, remaining problems of old driver are fixed, such as:
 - proper handling of hardware variants,
 - synchronization on SMP systems,
 - handling of boundary parameter values,
 - hardware sharing with PWM clocksource driver,
 - undefined state of PWM output after stopping PWM channel.
Signed-off-by: NTomasz Figa <tomasz.figa@gmail.com>
Reviewed-by: NSylwester Nawrocki <s.nawrocki@samsung.com>
Tested-by: NHeiko Stuebner <heiko@sntech.de>
Tested-by: NMark Brown <broonie@linaro.org>
Tested-by: NSylwester Nawrocki <sylvester.nawrocki@gmail.com>
Acked-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NThierry Reding <thierry.reding@gmail.com>

drivers/pwm/Makefile

@@ -12,6 +12,7 @@ obj-$(CONFIG_PWM_PUV3)		+= pwm-puv3.o
 obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o
 obj-$(CONFIG_PWM_RENESAS_TPU)	+= pwm-renesas-tpu.o
 obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung-legacy.o
+obj-$(CONFIG_PWM_SAMSUNG)	+= pwm-samsung.o
 obj-$(CONFIG_PWM_SPEAR)		+= pwm-spear.o
 obj-$(CONFIG_PWM_TEGRA)		+= pwm-tegra.o
 obj-$(CONFIG_PWM_TIECAP)	+= pwm-tiecap.o

drivers/pwm/pwm-samsung.c

+/*
+ * Copyright (c) 2007 Ben Dooks
+ * Copyright (c) 2008 Simtec Electronics
+ *     Ben Dooks <ben@simtec.co.uk>, <ben-linux@fluff.org>
+ * Copyright (c) 2013 Tomasz Figa <tomasz.figa@gmail.com>
+ *
+ * PWM driver for Samsung SoCs
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License.
+ */
+
+#include <linux/bitops.h>
+#include <linux/clk.h>
+#include <linux/export.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/time.h>
+
+/* For struct samsung_timer_variant and samsung_pwm_lock. */
+#include <clocksource/samsung_pwm.h>
+
+#define REG_TCFG0			0x00
+#define REG_TCFG1			0x04
+#define REG_TCON			0x08
+
+#define REG_TCNTB(chan)			(0x0c + ((chan) * 0xc))
+#define REG_TCMPB(chan)			(0x10 + ((chan) * 0xc))
+
+#define TCFG0_PRESCALER_MASK		0xff
+#define TCFG0_PRESCALER1_SHIFT		8
+
+#define TCFG1_MUX_MASK			0xf
+#define TCFG1_SHIFT(chan)		(4 * (chan))
+
+/*
+ * Each channel occupies 4 bits in TCON register, but there is a gap of 4
+ * bits (one channel) after channel 0, so channels have different numbering
+ * when accessing TCON register. See to_tcon_channel() function.
+ *
+ * In addition, the location of autoreload bit for channel 4 (TCON channel 5)
+ * in its set of bits is 2 as opposed to 3 for other channels.
+ */
+#define TCON_START(chan)		BIT(4 * (chan) + 0)
+#define TCON_MANUALUPDATE(chan)		BIT(4 * (chan) + 1)
+#define TCON_INVERT(chan)		BIT(4 * (chan) + 2)
+#define _TCON_AUTORELOAD(chan)		BIT(4 * (chan) + 3)
+#define _TCON_AUTORELOAD4(chan)		BIT(4 * (chan) + 2)
+#define TCON_AUTORELOAD(chan)		\
+	((chan < 5) ? _TCON_AUTORELOAD(chan) : _TCON_AUTORELOAD4(chan))
+
+/**
+ * struct samsung_pwm_channel - private data of PWM channel
+ * @period_ns:	current period in nanoseconds programmed to the hardware
+ * @duty_ns:	current duty time in nanoseconds programmed to the hardware
+ * @tin_ns:	time of one timer tick in nanoseconds with current timer rate
+ */
+struct samsung_pwm_channel {
+	u32 period_ns;
+	u32 duty_ns;
+	u32 tin_ns;
+};
+
+/**
+ * struct samsung_pwm_chip - private data of PWM chip
+ * @chip:		generic PWM chip
+ * @variant:		local copy of hardware variant data
+ * @inverter_mask:	inverter status for all channels - one bit per channel
+ * @base:		base address of mapped PWM registers
+ * @base_clk:		base clock used to drive the timers
+ * @tclk0:		external clock 0 (can be ERR_PTR if not present)
+ * @tclk1:		external clock 1 (can be ERR_PTR if not present)
+ */
+struct samsung_pwm_chip {
+	struct pwm_chip chip;
+	struct samsung_pwm_variant variant;
+	u8 inverter_mask;
+
+	void __iomem *base;
+	struct clk *base_clk;
+	struct clk *tclk0;
+	struct clk *tclk1;
+};
+
+#ifndef CONFIG_CLKSRC_SAMSUNG_PWM
+/*
+ * PWM block is shared between pwm-samsung and samsung_pwm_timer drivers
+ * and some registers need access synchronization. If both drivers are
+ * compiled in, the spinlock is defined in the clocksource driver,
+ * otherwise following definition is used.
+ *
+ * Currently we do not need any more complex synchronization method
+ * because all the supported SoCs contain only one instance of the PWM
+ * IP. Should this change, both drivers will need to be modified to
+ * properly synchronize accesses to particular instances.
+ */
+static DEFINE_SPINLOCK(samsung_pwm_lock);
+#endif
+
+static inline
+struct samsung_pwm_chip *to_samsung_pwm_chip(struct pwm_chip *chip)
+{
+	return container_of(chip, struct samsung_pwm_chip, chip);
+}
+
+static inline unsigned int to_tcon_channel(unsigned int channel)
+{
+	/* TCON register has a gap of 4 bits (1 channel) after channel 0 */
+	return (channel == 0) ? 0 : (channel + 1);
+}
+
+static void pwm_samsung_set_divisor(struct samsung_pwm_chip *pwm,
+				    unsigned int channel, u8 divisor)
+{
+	u8 shift = TCFG1_SHIFT(channel);
+	unsigned long flags;
+	u32 reg;
+	u8 bits;
+
+	bits = (fls(divisor) - 1) - pwm->variant.div_base;
+
+	spin_lock_irqsave(&samsung_pwm_lock, flags);
+
+	reg = readl(pwm->base + REG_TCFG1);
+	reg &= ~(TCFG1_MUX_MASK << shift);
+	reg |= bits << shift;
+	writel(reg, pwm->base + REG_TCFG1);
+
+	spin_unlock_irqrestore(&samsung_pwm_lock, flags);
+}
+
+static int pwm_samsung_is_tdiv(struct samsung_pwm_chip *chip, unsigned int chan)
+{
+	struct samsung_pwm_variant *variant = &chip->variant;
+	u32 reg;
+
+	reg = readl(chip->base + REG_TCFG1);
+	reg >>= TCFG1_SHIFT(chan);
+	reg &= TCFG1_MUX_MASK;
+
+	return (BIT(reg) & variant->tclk_mask) == 0;
+}
+
+static unsigned long pwm_samsung_get_tin_rate(struct samsung_pwm_chip *chip,
+					      unsigned int chan)
+{
+	unsigned long rate;
+	u32 reg;
+
+	rate = clk_get_rate(chip->base_clk);
+
+	reg = readl(chip->base + REG_TCFG0);
+	if (chan >= 2)
+		reg >>= TCFG0_PRESCALER1_SHIFT;
+	reg &= TCFG0_PRESCALER_MASK;
+
+	return rate / (reg + 1);
+}
+
+static unsigned long pwm_samsung_calc_tin(struct samsung_pwm_chip *chip,
+					  unsigned int chan, unsigned long freq)
+{
+	struct samsung_pwm_variant *variant = &chip->variant;
+	unsigned long rate;
+	struct clk *clk;
+	u8 div;
+
+	if (!pwm_samsung_is_tdiv(chip, chan)) {
+		clk = (chan < 2) ? chip->tclk0 : chip->tclk1;
+		if (!IS_ERR(clk)) {
+			rate = clk_get_rate(clk);
+			if (rate)
+				return rate;
+		}
+
+		dev_warn(chip->chip.dev,
+			"tclk of PWM %d is inoperational, using tdiv\n", chan);
+	}
+
+	rate = pwm_samsung_get_tin_rate(chip, chan);
+	dev_dbg(chip->chip.dev, "tin parent at %lu\n", rate);
+
+	/*
+	 * Compare minimum PWM frequency that can be achieved with possible
+	 * divider settings and choose the lowest divisor that can generate
+	 * frequencies lower than requested.
+	 */
+	for (div = variant->div_base; div < 4; ++div)
+		if ((rate >> (variant->bits + div)) < freq)
+			break;
+
+	pwm_samsung_set_divisor(chip, chan, BIT(div));
+
+	return rate >> div;
+}
+
+static int pwm_samsung_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
+	struct samsung_pwm_channel *our_chan;
+
+	if (!(our_chip->variant.output_mask & BIT(pwm->hwpwm))) {
+		dev_warn(chip->dev,
+			"tried to request PWM channel %d without output\n",
+			pwm->hwpwm);
+		return -EINVAL;
+	}
+
+	our_chan = devm_kzalloc(chip->dev, sizeof(*our_chan), GFP_KERNEL);
+	if (!our_chan)
+		return -ENOMEM;
+
+	pwm_set_chip_data(pwm, our_chan);
+
+	return 0;
+}
+
+static void pwm_samsung_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	pwm_set_chip_data(pwm, NULL);
+	devm_kfree(chip->dev, pwm_get_chip_data(pwm));
+}
+
+static int pwm_samsung_enable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
+	unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm);
+	unsigned long flags;
+	u32 tcon;
+
+	spin_lock_irqsave(&samsung_pwm_lock, flags);
+
+	tcon = readl(our_chip->base + REG_TCON);
+
+	tcon &= ~TCON_START(tcon_chan);
+	tcon |= TCON_MANUALUPDATE(tcon_chan);
+	writel(tcon, our_chip->base + REG_TCON);
+
+	tcon &= ~TCON_MANUALUPDATE(tcon_chan);
+	tcon |= TCON_START(tcon_chan) | TCON_AUTORELOAD(tcon_chan);
+	writel(tcon, our_chip->base + REG_TCON);
+
+	spin_unlock_irqrestore(&samsung_pwm_lock, flags);
+
+	return 0;
+}
+
+static void pwm_samsung_disable(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
+	unsigned int tcon_chan = to_tcon_channel(pwm->hwpwm);
+	unsigned long flags;
+	u32 tcon;
+
+	spin_lock_irqsave(&samsung_pwm_lock, flags);
+
+	tcon = readl(our_chip->base + REG_TCON);
+	tcon &= ~TCON_AUTORELOAD(tcon_chan);
+	writel(tcon, our_chip->base + REG_TCON);
+
+	spin_unlock_irqrestore(&samsung_pwm_lock, flags);
+}
+
+static int pwm_samsung_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			      int duty_ns, int period_ns)
+{
+	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
+	struct samsung_pwm_channel *chan = pwm_get_chip_data(pwm);
+	u32 tin_ns = chan->tin_ns, tcnt, tcmp;
+
+	/*
+	 * We currently avoid using 64bit arithmetic by using the
+	 * fact that anything faster than 1Hz is easily representable
+	 * by 32bits.
+	 */
+	if (period_ns > NSEC_PER_SEC)
+		return -ERANGE;
+
+	if (period_ns == chan->period_ns && duty_ns == chan->duty_ns)
+		return 0;
+
+	tcnt = readl(our_chip->base + REG_TCNTB(pwm->hwpwm));
+
+	/* We need tick count for calculation, not last tick. */
+	++tcnt;
+
+	/* Check to see if we are changing the clock rate of the PWM. */
+	if (chan->period_ns != period_ns) {
+		unsigned long tin_rate;
+		u32 period;
+
+		period = NSEC_PER_SEC / period_ns;
+
+		dev_dbg(our_chip->chip.dev, "duty_ns=%d, period_ns=%d (%u)\n",
+						duty_ns, period_ns, period);
+
+		tin_rate = pwm_samsung_calc_tin(our_chip, pwm->hwpwm, period);
+
+		dev_dbg(our_chip->chip.dev, "tin_rate=%lu\n", tin_rate);
+
+		tin_ns = NSEC_PER_SEC / tin_rate;
+		tcnt = period_ns / tin_ns;
+	}
+
+	/* Period is too short. */
+	if (tcnt <= 1)
+		return -ERANGE;
+
+	/* Note that counters count down. */
+	tcmp = duty_ns / tin_ns;
+
+	/* 0% duty is not available */
+	if (!tcmp)
+		++tcmp;
+
+	tcmp = tcnt - tcmp;
+
+	/* Decrement to get tick numbers, instead of tick counts. */
+	--tcnt;
+	/* -1UL will give 100% duty. */
+	--tcmp;
+
+	dev_dbg(our_chip->chip.dev,
+				"tin_ns=%u, tcmp=%u/%u\n", tin_ns, tcmp, tcnt);
+
+	/* Update PWM registers. */
+	writel(tcnt, our_chip->base + REG_TCNTB(pwm->hwpwm));
+	writel(tcmp, our_chip->base + REG_TCMPB(pwm->hwpwm));
+
+	if (test_bit(PWMF_ENABLED, &pwm->flags))
+		pwm_samsung_enable(chip, pwm);
+
+	chan->period_ns = period_ns;
+	chan->tin_ns = tin_ns;
+	chan->duty_ns = duty_ns;
+
+	return 0;
+}
+
+static void pwm_samsung_set_invert(struct samsung_pwm_chip *chip,
+				   unsigned int channel, bool invert)
+{
+	unsigned int tcon_chan = to_tcon_channel(channel);
+	unsigned long flags;
+	u32 tcon;
+
+	spin_lock_irqsave(&samsung_pwm_lock, flags);
+
+	tcon = readl(chip->base + REG_TCON);
+
+	if (invert) {
+		chip->inverter_mask |= BIT(channel);
+		tcon |= TCON_INVERT(tcon_chan);
+	} else {
+		chip->inverter_mask &= ~BIT(channel);
+		tcon &= ~TCON_INVERT(tcon_chan);
+	}
+
+	writel(tcon, chip->base + REG_TCON);
+
+	spin_unlock_irqrestore(&samsung_pwm_lock, flags);
+}
+
+static int pwm_samsung_set_polarity(struct pwm_chip *chip,
+				    struct pwm_device *pwm,
+				    enum pwm_polarity polarity)
+{
+	struct samsung_pwm_chip *our_chip = to_samsung_pwm_chip(chip);
+	bool invert = (polarity == PWM_POLARITY_NORMAL);
+
+	/* Inverted means normal in the hardware. */
+	pwm_samsung_set_invert(our_chip, pwm->hwpwm, invert);
+
+	return 0;
+}
+
+static const struct pwm_ops pwm_samsung_ops = {
+	.request	= pwm_samsung_request,
+	.free		= pwm_samsung_free,
+	.enable		= pwm_samsung_enable,
+	.disable	= pwm_samsung_disable,
+	.config		= pwm_samsung_config,
+	.set_polarity	= pwm_samsung_set_polarity,
+	.owner		= THIS_MODULE,
+};
+
+#ifdef CONFIG_OF
+static const struct samsung_pwm_variant s3c24xx_variant = {
+	.bits		= 16,
+	.div_base	= 1,
+	.has_tint_cstat	= false,
+	.tclk_mask	= BIT(4),
+};
+
+static const struct samsung_pwm_variant s3c64xx_variant = {
+	.bits		= 32,
+	.div_base	= 0,
+	.has_tint_cstat	= true,
+	.tclk_mask	= BIT(7) | BIT(6) | BIT(5),
+};
+
+static const struct samsung_pwm_variant s5p64x0_variant = {
+	.bits		= 32,
+	.div_base	= 0,
+	.has_tint_cstat	= true,
+	.tclk_mask	= 0,
+};
+
+static const struct samsung_pwm_variant s5pc100_variant = {
+	.bits		= 32,
+	.div_base	= 0,
+	.has_tint_cstat	= true,
+	.tclk_mask	= BIT(5),
+};
+
+static const struct of_device_id samsung_pwm_matches[] = {
+	{ .compatible = "samsung,s3c2410-pwm", .data = &s3c24xx_variant },
+	{ .compatible = "samsung,s3c6400-pwm", .data = &s3c64xx_variant },
+	{ .compatible = "samsung,s5p6440-pwm", .data = &s5p64x0_variant },
+	{ .compatible = "samsung,s5pc100-pwm", .data = &s5pc100_variant },
+	{ .compatible = "samsung,exynos4210-pwm", .data = &s5p64x0_variant },
+	{},
+};
+
+static int pwm_samsung_parse_dt(struct samsung_pwm_chip *chip)
+{
+	struct device_node *np = chip->chip.dev->of_node;
+	const struct of_device_id *match;
+	struct property *prop;
+	const __be32 *cur;
+	u32 val;
+
+	match = of_match_node(samsung_pwm_matches, np);
+	if (!match)
+		return -ENODEV;
+
+	memcpy(&chip->variant, match->data, sizeof(chip->variant));
+
+	of_property_for_each_u32(np, "samsung,pwm-outputs", prop, cur, val) {
+		if (val >= SAMSUNG_PWM_NUM) {
+			dev_err(chip->chip.dev,
+				"%s: invalid channel index in samsung,pwm-outputs property\n",
+								__func__);
+			continue;
+		}
+		chip->variant.output_mask |= BIT(val);
+	}
+
+	return 0;
+}
+#else
+static int pwm_samsung_parse_dt(struct samsung_pwm_chip *chip)
+{
+	return -ENODEV;
+}
+#endif
+
+static int pwm_samsung_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct samsung_pwm_chip *chip;
+	struct resource *res;
+	unsigned int chan;
+	int ret;
+
+	chip = devm_kzalloc(&pdev->dev, sizeof(*chip), GFP_KERNEL);
+	if (chip == NULL)
+		return -ENOMEM;
+
+	chip->chip.dev = &pdev->dev;
+	chip->chip.ops = &pwm_samsung_ops;
+	chip->chip.base = -1;
+	chip->chip.npwm = SAMSUNG_PWM_NUM;
+	chip->inverter_mask = BIT(SAMSUNG_PWM_NUM) - 1;
+
+	if (IS_ENABLED(CONFIG_OF) && pdev->dev.of_node) {
+		ret = pwm_samsung_parse_dt(chip);
+		if (ret)
+			return ret;
+
+		chip->chip.of_xlate = of_pwm_xlate_with_flags;
+		chip->chip.of_pwm_n_cells = 3;
+	} else {
+		if (!pdev->dev.platform_data) {
+			dev_err(&pdev->dev, "no platform data specified\n");
+			return -EINVAL;
+		}
+
+		memcpy(&chip->variant, pdev->dev.platform_data,
+							sizeof(chip->variant));
+	}
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	chip->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(chip->base))
+		return PTR_ERR(chip->base);
+
+	chip->base_clk = devm_clk_get(&pdev->dev, "timers");
+	if (IS_ERR(chip->base_clk)) {
+		dev_err(dev, "failed to get timer base clk\n");
+		return PTR_ERR(chip->base_clk);
+	}
+
+	ret = clk_prepare_enable(chip->base_clk);
+	if (ret < 0) {
+		dev_err(dev, "failed to enable base clock\n");
+		return ret;
+	}
+
+	for (chan = 0; chan < SAMSUNG_PWM_NUM; ++chan)
+		if (chip->variant.output_mask & BIT(chan))
+			pwm_samsung_set_invert(chip, chan, true);
+
+	/* Following clocks are optional. */
+	chip->tclk0 = devm_clk_get(&pdev->dev, "pwm-tclk0");
+	chip->tclk1 = devm_clk_get(&pdev->dev, "pwm-tclk1");
+
+	platform_set_drvdata(pdev, chip);
+
+	ret = pwmchip_add(&chip->chip);
+	if (ret < 0) {
+		dev_err(dev, "failed to register PWM chip\n");
+		clk_disable_unprepare(chip->base_clk);
+		return ret;
+	}
+
+	dev_dbg(dev, "base_clk at %lu, tclk0 at %lu, tclk1 at %lu\n",
+		clk_get_rate(chip->base_clk),
+		!IS_ERR(chip->tclk0) ? clk_get_rate(chip->tclk0) : 0,
+		!IS_ERR(chip->tclk1) ? clk_get_rate(chip->tclk1) : 0);
+
+	return 0;
+}
+
+static int pwm_samsung_remove(struct platform_device *pdev)
+{
+	struct samsung_pwm_chip *chip = platform_get_drvdata(pdev);
+	int ret;
+
+	ret = pwmchip_remove(&chip->chip);
+	if (ret < 0)
+		return ret;
+
+	clk_disable_unprepare(chip->base_clk);
+
+	return 0;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int pwm_samsung_suspend(struct device *dev)
+{
+	struct samsung_pwm_chip *chip = dev_get_drvdata(dev);
+	unsigned int i;
+
+	/*
+	 * No one preserves these values during suspend so reset them.
+	 * Otherwise driver leaves PWM unconfigured if same values are
+	 * passed to pwm_config() next time.
+	 */
+	for (i = 0; i < SAMSUNG_PWM_NUM; ++i) {
+		struct pwm_device *pwm = &chip->chip.pwms[i];
+		struct samsung_pwm_channel *chan = pwm_get_chip_data(pwm);
+
+		if (!chan)
+			continue;
+
+		chan->period_ns = 0;
+		chan->duty_ns = 0;
+	}
+
+	return 0;
+}
+
+static int pwm_samsung_resume(struct device *dev)
+{
+	struct samsung_pwm_chip *chip = dev_get_drvdata(dev);
+	unsigned int chan;
+
+	/*
+	 * Inverter setting must be preserved across suspend/resume
+	 * as nobody really seems to configure it more than once.
+	 */
+	for (chan = 0; chan < SAMSUNG_PWM_NUM; ++chan) {
+		if (chip->variant.output_mask & BIT(chan))
+			pwm_samsung_set_invert(chip, chan,
+					chip->inverter_mask & BIT(chan));
+	}
+
+	return 0;
+}
+#endif
+
+static const struct dev_pm_ops pwm_samsung_pm_ops = {
+	SET_SYSTEM_SLEEP_PM_OPS(pwm_samsung_suspend, pwm_samsung_resume)
+};
+
+static struct platform_driver pwm_samsung_driver = {
+	.driver		= {
+		.name	= "samsung-pwm",
+		.owner	= THIS_MODULE,
+		.pm	= &pwm_samsung_pm_ops,
+		.of_match_table = of_match_ptr(samsung_pwm_matches),
+	},
+	.probe		= pwm_samsung_probe,
+	.remove		= pwm_samsung_remove,
+};
+module_platform_driver(pwm_samsung_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Tomasz Figa <tomasz.figa@gmail.com>");
+MODULE_ALIAS("platform:samsung-pwm");

include/clocksource/samsung_pwm.h

@@ -20,7 +20,14 @@
 
 #define SAMSUNG_PWM_NUM		5
 
+/*
+ * Following declaration must be in an ifdef due to this symbol being static
+ * in pwm-samsung driver if the clocksource driver is not compiled in and the
+ * spinlock is not shared between both drivers.
+ */
+#ifdef CONFIG_CLKSRC_SAMSUNG_PWM
 extern spinlock_t samsung_pwm_lock;
+#endif
 
 struct samsung_pwm_variant {
 	u8 bits;