Basic PWM driver for AVR32 and AT91

PWM device setup, and a simple PWM driver exposing a programming interface
giving access to each channel's full capabilities.  Note that this doesn't
support starting several channels in synch.

[[email protected]: allocate platform device dynamically]
[[email protected]: Kconfig fix]
Signed-off-by: David Brownell <[email protected]>
Signed-off-by: Haavard Skinnemoen <[email protected]>
Cc: Andrew Victor <[email protected]>
Cc: Nicolas Ferre <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/misc/Kconfig

@@ -13,6 +13,15 @@ menuconfig MISC_DEVICES
 
 if MISC_DEVICES
 
+config ATMEL_PWM
+	tristate "Atmel AT32/AT91 PWM support"
+	depends on AVR32 || ARCH_AT91
+	help
+	  This option enables device driver support for the PWM channels
+	  on certain Atmel prcoessors.  Pulse Width Modulation is used for
+	  purposes including software controlled power-efficent backlights
+	  on LCD displays, motor control, and waveform generation.
+
 config IBM_ASM
 	tristate "Device driver for IBM RSA service processor"
 	depends on X86 && PCI && INPUT && EXPERIMENTAL

drivers/misc/Makefile

@@ -8,6 +8,7 @@ obj-$(CONFIG_HDPU_FEATURES)	+= hdpuftrs/
 obj-$(CONFIG_MSI_LAPTOP)     += msi-laptop.o
 obj-$(CONFIG_ACER_WMI)     += acer-wmi.o
 obj-$(CONFIG_ASUS_LAPTOP)     += asus-laptop.o
+obj-$(CONFIG_ATMEL_PWM)		+= atmel_pwm.o
 obj-$(CONFIG_ATMEL_SSC)		+= atmel-ssc.o
 obj-$(CONFIG_TC1100_WMI)	+= tc1100-wmi.o
 obj-$(CONFIG_LKDTM)		+= lkdtm.o

drivers/misc/atmel_pwm.c

@@ -0,0 +1,409 @@
+#include <linux/module.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+#include <linux/atmel_pwm.h>
+
+
+/*
+ * This is a simple driver for the PWM controller found in various newer
+ * Atmel SOCs, including the AVR32 series and the AT91sam9263.
+ *
+ * Chips with current Linux ports have only 4 PWM channels, out of max 32.
+ * AT32UC3A and AT32UC3B chips have 7 channels (but currently no Linux).
+ * Docs are inconsistent about the width of the channel counter registers;
+ * it's at least 16 bits, but several places say 20 bits.
+ */
+#define	PWM_NCHAN	4		/* max 32 */
+
+struct pwm {
+	spinlock_t		lock;
+	struct platform_device	*pdev;
+	u32			mask;
+	int			irq;
+	void __iomem		*base;
+	struct clk		*clk;
+	struct pwm_channel	*channel[PWM_NCHAN];
+	void			(*handler[PWM_NCHAN])(struct pwm_channel *);
+};
+
+
+/* global PWM controller registers */
+#define PWM_MR		0x00
+#define PWM_ENA		0x04
+#define PWM_DIS		0x08
+#define PWM_SR		0x0c
+#define PWM_IER		0x10
+#define PWM_IDR		0x14
+#define PWM_IMR		0x18
+#define PWM_ISR		0x1c
+
+static inline void pwm_writel(const struct pwm *p, unsigned offset, u32 val)
+{
+	__raw_writel(val, p->base + offset);
+}
+
+static inline u32 pwm_readl(const struct pwm *p, unsigned offset)
+{
+	return __raw_readl(p->base + offset);
+}
+
+static inline void __iomem *pwmc_regs(const struct pwm *p, int index)
+{
+	return p->base + 0x200 + index * 0x20;
+}
+
+static struct pwm *pwm;
+
+static void pwm_dumpregs(struct pwm_channel *ch, char *tag)
+{
+	struct device	*dev = &pwm->pdev->dev;
+
+	dev_dbg(dev, "%s: mr %08x, sr %08x, imr %08x\n",
+		tag,
+		pwm_readl(pwm, PWM_MR),
+		pwm_readl(pwm, PWM_SR),
+		pwm_readl(pwm, PWM_IMR));
+	dev_dbg(dev,
+		"pwm ch%d - mr %08x, dty %u, prd %u, cnt %u\n",
+		ch->index,
+		pwm_channel_readl(ch, PWM_CMR),
+		pwm_channel_readl(ch, PWM_CDTY),
+		pwm_channel_readl(ch, PWM_CPRD),
+		pwm_channel_readl(ch, PWM_CCNT));
+}
+
+
+/**
+ * pwm_channel_alloc - allocate an unused PWM channel
+ * @index: identifies the channel
+ * @ch: structure to be initialized
+ *
+ * Drivers allocate PWM channels according to the board's wiring, and
+ * matching board-specific setup code.  Returns zero or negative errno.
+ */
+int pwm_channel_alloc(int index, struct pwm_channel *ch)
+{
+	unsigned long	flags;
+	int		status = 0;
+
+	/* insist on PWM init, with this signal pinned out */
+	if (!pwm || !(pwm->mask & 1 << index))
+		return -ENODEV;
+
+	if (index < 0 || index >= PWM_NCHAN || !ch)
+		return -EINVAL;
+	memset(ch, 0, sizeof *ch);
+
+	spin_lock_irqsave(&pwm->lock, flags);
+	if (pwm->channel[index])
+		status = -EBUSY;
+	else {
+		clk_enable(pwm->clk);
+
+		ch->regs = pwmc_regs(pwm, index);
+		ch->index = index;
+
+		/* REVISIT: ap7000 seems to go 2x as fast as we expect!! */
+		ch->mck = clk_get_rate(pwm->clk);
+
+		pwm->channel[index] = ch;
+		pwm->handler[index] = NULL;
+
+		/* channel and irq are always disabled when we return */
+		pwm_writel(pwm, PWM_DIS, 1 << index);
+		pwm_writel(pwm, PWM_IDR, 1 << index);
+	}
+	spin_unlock_irqrestore(&pwm->lock, flags);
+	return status;
+}
+EXPORT_SYMBOL(pwm_channel_alloc);
+
+static int pwmcheck(struct pwm_channel *ch)
+{
+	int		index;
+
+	if (!pwm)
+		return -ENODEV;
+	if (!ch)
+		return -EINVAL;
+	index = ch->index;
+	if (index < 0 || index >= PWM_NCHAN || pwm->channel[index] != ch)
+		return -EINVAL;
+
+	return index;
+}
+
+/**
+ * pwm_channel_free - release a previously allocated channel
+ * @ch: the channel being released
+ *
+ * The channel is completely shut down (counter and IRQ disabled),
+ * and made available for re-use.  Returns zero, or negative errno.
+ */
+int pwm_channel_free(struct pwm_channel *ch)
+{
+	unsigned long	flags;
+	int		t;
+
+	spin_lock_irqsave(&pwm->lock, flags);
+	t = pwmcheck(ch);
+	if (t >= 0) {
+		pwm->channel[t] = NULL;
+		pwm->handler[t] = NULL;
+
+		/* channel and irq are always disabled when we return */
+		pwm_writel(pwm, PWM_DIS, 1 << t);
+		pwm_writel(pwm, PWM_IDR, 1 << t);
+
+		clk_disable(pwm->clk);
+		t = 0;
+	}
+	spin_unlock_irqrestore(&pwm->lock, flags);
+	return t;
+}
+EXPORT_SYMBOL(pwm_channel_free);
+
+int __pwm_channel_onoff(struct pwm_channel *ch, int enabled)
+{
+	unsigned long	flags;
+	int		t;
+
+	/* OMITTED FUNCTIONALITY:  starting several channels in synch */
+
+	spin_lock_irqsave(&pwm->lock, flags);
+	t = pwmcheck(ch);
+	if (t >= 0) {
+		pwm_writel(pwm, enabled ? PWM_ENA : PWM_DIS, 1 << t);
+		t = 0;
+		pwm_dumpregs(ch, enabled ? "enable" : "disable");
+	}
+	spin_unlock_irqrestore(&pwm->lock, flags);
+
+	return t;
+}
+EXPORT_SYMBOL(__pwm_channel_onoff);
+
+/**
+ * pwm_clk_alloc - allocate and configure CLKA or CLKB
+ * @prescale: from 0..10, the power of two used to divide MCK
+ * @div: from 1..255, the linear divisor to use
+ *
+ * Returns PWM_CPR_CLKA, PWM_CPR_CLKB, or negative errno.  The allocated
+ * clock will run with a period of (2^prescale * div) / MCK, or twice as
+ * long if center aligned PWM output is used.  The clock must later be
+ * deconfigured using pwm_clk_free().
+ */
+int pwm_clk_alloc(unsigned prescale, unsigned div)
+{
+	unsigned long	flags;
+	u32		mr;
+	u32		val = (prescale << 8) | div;
+	int		ret = -EBUSY;
+
+	if (prescale >= 10 || div == 0 || div > 255)
+		return -EINVAL;
+
+	spin_lock_irqsave(&pwm->lock, flags);
+	mr = pwm_readl(pwm, PWM_MR);
+	if ((mr & 0xffff) == 0) {
+		mr |= val;
+		ret = PWM_CPR_CLKA;
+	}
+	if ((mr & (0xffff << 16)) == 0) {
+		mr |= val << 16;
+		ret = PWM_CPR_CLKB;
+	}
+	if (ret > 0)
+		pwm_writel(pwm, PWM_MR, mr);
+	spin_unlock_irqrestore(&pwm->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(pwm_clk_alloc);
+
+/**
+ * pwm_clk_free - deconfigure and release CLKA or CLKB
+ *
+ * Reverses the effect of pwm_clk_alloc().
+ */
+void pwm_clk_free(unsigned clk)
+{
+	unsigned long	flags;
+	u32		mr;
+
+	spin_lock_irqsave(&pwm->lock, flags);
+	mr = pwm_readl(pwm, PWM_MR);
+	if (clk == PWM_CPR_CLKA)
+		pwm_writel(pwm, PWM_MR, mr & ~(0xffff << 0));
+	if (clk == PWM_CPR_CLKB)
+		pwm_writel(pwm, PWM_MR, mr & ~(0xffff << 16));
+	spin_unlock_irqrestore(&pwm->lock, flags);
+}
+EXPORT_SYMBOL(pwm_clk_free);
+
+/**
+ * pwm_channel_handler - manage channel's IRQ handler
+ * @ch: the channel
+ * @handler: the handler to use, possibly NULL
+ *
+ * If the handler is non-null, the handler will be called after every
+ * period of this PWM channel.  If the handler is null, this channel
+ * won't generate an IRQ.
+ */
+int pwm_channel_handler(struct pwm_channel *ch,
+		void (*handler)(struct pwm_channel *ch))
+{
+	unsigned long	flags;
+	int		t;
+
+	spin_lock_irqsave(&pwm->lock, flags);
+	t = pwmcheck(ch);
+	if (t >= 0) {
+		pwm->handler[t] = handler;
+		pwm_writel(pwm, handler ? PWM_IER : PWM_IDR, 1 << t);
+		t = 0;
+	}
+	spin_unlock_irqrestore(&pwm->lock, flags);
+
+	return t;
+}
+EXPORT_SYMBOL(pwm_channel_handler);
+
+static irqreturn_t pwm_irq(int id, void *_pwm)
+{
+	struct pwm	*p = _pwm;
+	irqreturn_t	handled = IRQ_NONE;
+	u32		irqstat;
+	int		index;
+
+	spin_lock(&p->lock);
+
+	/* ack irqs, then handle them */
+	irqstat = pwm_readl(pwm, PWM_ISR);
+
+	while (irqstat) {
+		struct pwm_channel *ch;
+		void (*handler)(struct pwm_channel *ch);
+
+		index = ffs(irqstat) - 1;
+		irqstat &= ~(1 << index);
+		ch = pwm->channel[index];
+		handler = pwm->handler[index];
+		if (handler && ch) {
+			spin_unlock(&p->lock);
+			handler(ch);
+			spin_lock(&p->lock);
+			handled = IRQ_HANDLED;
+		}
+	}
+
+	spin_unlock(&p->lock);
+	return handled;
+}
+
+static int __init pwm_probe(struct platform_device *pdev)
+{
+	struct resource *r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	int irq = platform_get_irq(pdev, 0);
+	u32 *mp = pdev->dev.platform_data;
+	struct pwm *p;
+	int status = -EIO;
+
+	if (pwm)
+		return -EBUSY;
+	if (!r || irq < 0 || !mp || !*mp)
+		return -ENODEV;
+	if (*mp & ~((1<<PWM_NCHAN)-1)) {
+		dev_warn(&pdev->dev, "mask 0x%x ... more than %d channels\n",
+			*mp, PWM_NCHAN);
+		return -EINVAL;
+	}
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+
+	spin_lock_init(&p->lock);
+	p->pdev = pdev;
+	p->mask = *mp;
+	p->irq = irq;
+	p->base = ioremap(r->start, r->end - r->start + 1);
+	if (!p->base)
+		goto fail;
+	p->clk = clk_get(&pdev->dev, "mck");
+	if (IS_ERR(p->clk)) {
+		status = PTR_ERR(p->clk);
+		p->clk = NULL;
+		goto fail;
+	}
+
+	status = request_irq(irq, pwm_irq, 0, pdev->name, p);
+	if (status < 0)
+		goto fail;
+
+	pwm = p;
+	platform_set_drvdata(pdev, p);
+
+	return 0;
+
+fail:
+	if (p->clk)
+		clk_put(p->clk);
+	if (p->base)
+		iounmap(p->base);
+
+	kfree(p);
+	return status;
+}
+
+static int __exit pwm_remove(struct platform_device *pdev)
+{
+	struct pwm *p = platform_get_drvdata(pdev);
+
+	if (p != pwm)
+		return -EINVAL;
+
+	clk_enable(pwm->clk);
+	pwm_writel(pwm, PWM_DIS, (1 << PWM_NCHAN) - 1);
+	pwm_writel(pwm, PWM_IDR, (1 << PWM_NCHAN) - 1);
+	clk_disable(pwm->clk);
+
+	pwm = NULL;
+
+	free_irq(p->irq, p);
+	clk_put(p->clk);
+	iounmap(p->base);
+	kfree(p);
+
+	return 0;
+}
+
+static struct platform_driver atmel_pwm_driver = {
+	.driver = {
+		.name = "atmel_pwm",
+		.owner = THIS_MODULE,
+	},
+	.remove = __exit_p(pwm_remove),
+
+	/* NOTE: PWM can keep running in AVR32 "idle" and "frozen" states;
+	 * and all AT91sam9263 states, albeit at reduced clock rate if
+	 * MCK becomes the slow clock (i.e. what Linux labels STR).
+	 */
+};
+
+static int __init pwm_init(void)
+{
+	return platform_driver_probe(&atmel_pwm_driver, pwm_probe);
+}
+module_init(pwm_init);
+
+static void __exit pwm_exit(void)
+{
+	platform_driver_unregister(&atmel_pwm_driver);
+}
+module_exit(pwm_exit);
+
+MODULE_DESCRIPTION("Driver for AT32/AT91 PWM module");
+MODULE_LICENSE("GPL");