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.

[hskinnemoen@atmel.com: allocate platform device dynamically]
[hskinnemoen@atmel.com: Kconfig fix]
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Andrew Victor <linux@maxim.org.za>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 70 insertions, 0 deletions

diff --git a/include/linux/atmel_pwm.h b/include/linux/atmel_pwm.h
new file mode 100644
index 0000000..ea04abb
--- /dev/null
+++ b/include/linux/atmel_pwm.h
@@ -0,0 +1,70 @@
+#ifndef __LINUX_ATMEL_PWM_H
+#define __LINUX_ATMEL_PWM_H
+
+/**
+ * struct pwm_channel - driver handle to a PWM channel
+ * @regs: base of this channel's registers
+ * @index: number of this channel (0..31)
+ * @mck: base clock rate, which can be prescaled and maybe subdivided
+ *
+ * Drivers initialize a pwm_channel structure using pwm_channel_alloc().
+ * Then they configure its clock rate (derived from MCK), alignment,
+ * polarity, and duty cycle by writing directly to the channel registers,
+ * before enabling the channel by calling pwm_channel_enable().
+ *
+ * After emitting a PWM signal for the desired length of time, drivers
+ * may then pwm_channel_disable() or pwm_channel_free().  Both of these
+ * disable the channel, but when it's freed the IRQ is deconfigured and
+ * the channel must later be re-allocated and reconfigured.
+ *
+ * Note that if the period or duty cycle need to be changed while the
+ * PWM channel is operating, drivers must use the PWM_CUPD double buffer
+ * mechanism, either polling until they change or getting implicitly
+ * notified through a once-per-period interrupt handler.
+ */
+struct pwm_channel {
+	void __iomem	*regs;
+	unsigned	index;
+	unsigned long	mck;
+};
+
+extern int pwm_channel_alloc(int index, struct pwm_channel *ch);
+extern int pwm_channel_free(struct pwm_channel *ch);
+
+extern int pwm_clk_alloc(unsigned prescale, unsigned div);
+extern void pwm_clk_free(unsigned clk);
+
+extern int __pwm_channel_onoff(struct pwm_channel *ch, int enabled);
+
+#define pwm_channel_enable(ch)	__pwm_channel_onoff((ch), 1)
+#define pwm_channel_disable(ch)	__pwm_channel_onoff((ch), 0)
+
+/* periodic interrupts, mostly for CUPD changes to period or cycle */
+extern int pwm_channel_handler(struct pwm_channel *ch,
+		void (*handler)(struct pwm_channel *ch));
+
+/* per-channel registers (banked at pwm_channel->regs) */
+#define PWM_CMR		0x00		/* mode register */
+#define		PWM_CPR_CPD	(1 << 10)	/* set: CUPD modifies period */
+#define		PWM_CPR_CPOL	(1 << 9)	/* set: idle high */
+#define		PWM_CPR_CALG	(1 << 8)	/* set: center align */
+#define		PWM_CPR_CPRE	(0xf << 0)	/* mask: rate is mck/(2^pre) */
+#define		PWM_CPR_CLKA	(0xb << 0)	/* rate CLKA */
+#define		PWM_CPR_CLKB	(0xc << 0)	/* rate CLKB */
+#define PWM_CDTY	0x04		/* duty cycle (max of CPRD) */
+#define PWM_CPRD	0x08		/* period (count up from zero) */
+#define PWM_CCNT	0x0c		/* counter (20 bits?) */
+#define PWM_CUPD	0x10		/* update CPRD (or CDTY) next period */
+
+static inline void
+pwm_channel_writel(struct pwm_channel *pwmc, unsigned offset, u32 val)
+{
+	__raw_writel(val, pwmc->regs + offset);
+}
+
+static inline u32 pwm_channel_readl(struct pwm_channel *pwmc, unsigned offset)
+{
+	return __raw_readl(pwmc->regs + offset);
+}
+
+#endif /* __LINUX_ATMEL_PWM_H */