Subject: [PATCH v3 11/18] pwm: Add new pwm-samsung driver

From: [email-masked] (Tomasz Figa)
Date: Sat, 22 Jun 2013 15:06:25 +0200

This patch introduces new Samsung PWM driver, which is heavily cleaned,
multiplatform aware and supports DeviceTree based instantiation.

Since on historical hardware PWM block can be shared with clocksource
driver, a shared spinlock is used to protect access to shared registers,
already exported from the clocksource driver.

Signed-off-by: Tomasz Figa <[email-masked]>
---
 drivers/pwm/Makefile      |   1 +
 drivers/pwm/pwm-samsung.c | 601 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 602 insertions(+)
 create mode 100644 drivers/pwm/pwm-samsung.c

Changes since v2:
 - Replaced __raw_{readl,writel} with {readl,writel}.
 - Corrected commit message.

diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 229a599..833c3ac 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
 obj-$(CONFIG_PWM_PUV3)		+= pwm-puv3.o
 obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o
 obj-$(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
diff --git a/drivers/pwm/pwm-samsung.c b/drivers/pwm/pwm-samsung.c
new file mode 100644
index 0000000..04fa29c
--- /dev/null
+++ b/drivers/pwm/pwm-samsung.c
@@ -0,0 +1,601 @@
+/*
+ * Copyright (c) 2007 Ben Dooks
+ * Copyright (c) 2008 Simtec Electronics
+ *     Ben Dooks <[email-masked]>, <[email-masked]>
+ * Copyright (c) 2013 Tomasz Figa <[email-masked]>
+ *
+ * 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(tmr)			(0x0c + ((tmr) * 0xc))
+#define REG_TCMPB(tmr)			(0x10 + ((tmr) * 0xc))
+
+#define TCFG0_PRESCALER_MASK		0xff
+#define TCFG0_PRESCALER1_SHIFT		8
+
+#define TCFG1_MUX_MASK			0xf
+#define TCFG1_SHIFT(x)			((x) * 4)
+
+#define TCON_START(chan)		(1 << (4 * (chan) + 0))
+#define TCON_MANUALUPDATE(chan)		(1 << (4 * (chan) + 1))
+#define TCON_INVERT(chan)		(1 << (4 * (chan) + 2))
+#define TCON_AUTORELOAD(chan)		(1 << (4 * (chan) \
+						+ (((chan) < 5) ? 3 : 2)))
+
+/**
+ * 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.
+ */
+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) */
+	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,
+};
+
+static const struct samsung_pwm_variant s5p_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 = &s5p_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) {
+			pr_warning("%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 (!chip->base)
+		return -ENOMEM;
+
+	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 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 <[email-masked]>");
+MODULE_ALIAS("platform:samsung-pwm");
-- 
1.8.2.1