/* Code to control digital step attenuators of the sysmocom RFDN board
 * (C) 2017 by Harald Welte <laforge@gnumonks.org>
 */
#include <stdio.h>
#include <errno.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/rcc.h>

#include "attenuator.h"
#include "utils.h"

static const struct attenuator_cfg *g_att_cfg;
static struct attenuator_state **g_att_state;

static void delay(void)
{
	volatile uint32_t i;
	for (i = 0; i < 10000; i++) { }
}

/* create a positive pulse on a given GPIO line */
static void gpio_pulse(uint32_t bank, uint32_t nr)
{
	gpio_set(bank, nr);
	/* FIXME: Some delay, 30ns for LE or CLK */
	delay();
	gpio_clear(bank, nr);
}

/* set the data line to high or low */
static void gpio_set_data(int high)
{
	if (high)
		gpio_set(g_att_cfg->gpio_data.bank, g_att_cfg->gpio_data.gpio_nr);
	else
		gpio_clear(g_att_cfg->gpio_data.bank, g_att_cfg->gpio_data.gpio_nr);
}

/* pulse the clock line with one positive pulse */
static void gpio_pulse_clk(void)
{
	gpio_pulse(g_att_cfg->gpio_clock.bank, g_att_cfg->gpio_clock.gpio_nr);
}

/* set a given attenuator to a given value
 * \param channel The RF channel (0..7)
 * \param stage Attenuator stage (0..1)
 * \param value in quarter-dB (0..124)
 */
int attenuator_set(uint8_t channel, uint8_t stage, uint8_t val_qdb)
{
	uint8_t val = val_qdb/4; /* whole dB for this attenuator */
	const struct attenuator_def *ad;
	int i;

	if (!g_att_cfg)
		return -ENODEV;

	if (channel >= g_att_cfg->num_channels)
		return -ENODEV;

	if (stage >= g_att_cfg->channels[channel].num_stages)
		return -ENODEV;

	ad = &g_att_cfg->channels[channel].stage[stage];

	if (val > 0x1f)
		return -ERANGE;

	/* The shift register should be loaded while LE is held low to
	 * prevent the attenuator value from changing as data is
	 * entered */
	for (i = 5; i >= 0; i--) {
		unsigned int bit = ((val >> i) & 1);
		gpio_set_data(bit);
		gpio_pulse_clk();
	}

	/* The LE input should then be toggled HIGH and brought LOW
	 * again, latching the new data. Minimum LE pulse width is 30ns */
	gpio_pulse(ad->le.bank, ad->le.gpio_nr);

	/* actual value we have set may not be exactly what was requested */
	g_att_state[channel][stage].value_qdB.current = val*4;

	return 0;
}

/* get current attenuator value in quarter-dB */
int attenuator_get(uint8_t channel, uint8_t stage, enum attenuator_value av)
{
	if (!g_att_cfg)
		return -ENODEV;

	if (channel >= g_att_cfg->num_channels)
		return -ENODEV;

	if (stage >= g_att_cfg->channels[channel].num_stages)
		return -ENODEV;

	switch (av) {
	case ATT_VAL_CURRENT:
		return g_att_state[channel][stage].value_qdB.current;
	case ATT_VAL_STARTUP:
		return g_att_state[channel][stage].value_qdB.startup;
	default:
		return -EINVAL;
	}
}

/* initialize the attenuator driver */
void attenuator_init(const struct attenuator_cfg *cfg,
		     struct attenuator_state **state)
{
	uint32_t banks[6] = { GPIOA, GPIOB, GPIOC, GPIOD, GPIOE, GPIOF };
	const uint32_t periph[6] = { RCC_GPIOA, RCC_GPIOB, RCC_GPIOC,
				     RCC_GPIOD, RCC_GPIOE, RCC_GPIOF };
	uint32_t pins[6] = {0, 0, 0, 0, 0, 0};
	unsigned int i, j, k;

	g_att_cfg = cfg;
	g_att_state = state;

	/* collect the bit mask of all LE pins for each bank */
	for (i = 0; i < g_att_cfg->num_channels; i++) {
		const struct attenuator_channel_def *ch = &g_att_cfg->channels[i];
		for (j = 0; j < ch->num_stages; j++) {
			const struct attenuator_def *at = &ch->stage[j];
			for (k = 0; k < ARRAY_SIZE(banks); k++) {
				if (at->le.bank != banks[k])
					continue;
				pins[k] |= at->le.gpio_nr;
			}
		}
	}

	/* add the shared DATA / CLOCK pins */
	for (k = 0; k < ARRAY_SIZE(banks); k++) {
		if (g_att_cfg->gpio_clock.bank == banks[k])
			pins[k] |= g_att_cfg->gpio_clock.gpio_nr;
		if (g_att_cfg->gpio_data.bank == banks[k])
			pins[k] |= g_att_cfg->gpio_data.gpio_nr;
	}

	/* configure the GPIO of each bank based on he collected pin-bitmasks */
	for (k = 0; k < ARRAY_SIZE(banks); k++) {
		if (!pins[k])
			continue;
		rcc_periph_clock_enable(periph[k]);
		gpio_set_mode(banks[k], GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, pins[k]);
	}
}