root/include/linux/atmel_pwm.h

DEFINITIONS

1. pwm_channel_writel
2. pwm_channel_readl

#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 */