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 000000000000..ea04abb3db8e
--- /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 */