/* libhw/rp2040_hwspi.c - <libhw/generic/spi.h> implementation for the RP2040's ARM Primecell SSP (PL022)
 *
 * Copyright (C) 2024-2025  Luke T. Shumaker <lukeshu@lukeshu.com>
 * SPDX-License-Identifier: AGPL-3.0-or-later
 */

#include <inttypes.h> /* for PRIu{n} */

#include <hardware/clocks.h> /* for clock_get_hz() and clk_peri */
#include <hardware/gpio.h>
#include <hardware/spi.h>

#include <libmisc/assert.h>

#define LOG_NAME RP2040_SPI
#include <libmisc/log.h>

#define IMPLEMENTATION_FOR_LIBHW_RP2040_HWSPI_H YES
#include <libhw/rp2040_hwspi.h>

#include <libhw/generic/alarmclock.h>

#include "config.h"

#ifndef CONFIG_RP2040_SPI_DEBUG
	#error config.h must define CONFIG_RP2040_SPI_DEBUG (bool)
#endif

LO_IMPLEMENTATION_C(io_duplex_readwriter, struct rp2040_hwspi, rp2040_hwspi, static)
LO_IMPLEMENTATION_C(spi, struct rp2040_hwspi, rp2040_hwspi, static)

#define assert_4distinct(a, b, c, d) \
	assert(a != b); \
	assert(a != c); \
	assert(a != d); \
	assert(b != c); \
	assert(b != d); \
	assert(c != d);

void _rp2040_hwspi_init(struct rp2040_hwspi *self,
                        enum rp2040_hwspi_instance inst_num,
                        enum spi_mode mode,
                        uint baudrate_hz,
                        uint64_t min_delay_ns,
                        uint8_t bogus_data,
                        uint pin_miso,
                        uint pin_mosi,
                        uint pin_clk,
                        uint pin_cs) {
	/* Be not weary: This is but 12 lines of actual code; and many
	 * lines of comments and assert()s.  */
	spi_inst_t *inst;
	uint actual_baudrate_hz;

	assert(self);
	assert(baudrate_hz);
	uint32_t clk_peri_hz = clock_get_hz(clk_peri);
	debugf("clk_peri = %"PRIu32"Hz", clk_peri_hz);
	assert(baudrate_hz*2 <= clk_peri_hz);
	assert_4distinct(pin_miso, pin_mosi, pin_clk, pin_cs);

	/* Regarding the constraints on pin assignments: see the
	 * RP2040 datasheet, table 2, in §1.4.3 "GPIO Functions".  */
	switch (inst_num) {
	case RP2040_HWSPI_0:
		inst = spi0;
		assert(pin_miso ==  0 || pin_miso ==  4 || pin_miso == 16 || pin_miso == 20);
		/*assert(pin_cs   ==  1 || pin_cs   ==  5 || pin_cs   == 17 || pin_cs   == 21);*/
		assert(pin_clk  ==  2 || pin_clk  ==  6 || pin_clk  == 18 || pin_clk  == 22);
		assert(pin_mosi ==  3 || pin_mosi ==  7 || pin_mosi == 19 || pin_mosi == 23);
		break;
	case RP2040_HWSPI_1:
		inst = spi1;
		assert(pin_miso ==  8 || pin_miso == 12 || pin_miso == 24 || pin_miso == 28);
		/*assert(pin_cs   ==  9 || pin_cs   == 13 || pin_cs   == 25 || pin_cs   == 29);*/
		assert(pin_clk  == 10 || pin_clk  == 14 || pin_clk  == 26);
		assert(pin_mosi == 11 || pin_mosi == 15 || pin_mosi == 27);
		break;
	default:
		assert_notreached("invalid hwspi instance number");
	}

	actual_baudrate_hz = spi_init(inst, baudrate_hz);
	debugf("baudrate = %uHz", actual_baudrate_hz);
	assert(actual_baudrate_hz == baudrate_hz);
	spi_set_format(inst, 8,
	               (mode & 0b10) ? SPI_CPOL_1 : SPI_CPOL_0,
	               (mode & 0b01) ? SPI_CPHA_1 : SPI_CPHA_0,
	               SPI_MSB_FIRST);

	/* Connect the pins to the PL022; set them each to "function
	 * 1" (again, see the RP2040 datasheet, table 2, in §1.4.3
	 * "GPIO Functions").
	 *
	 * ("GPIO_FUNC_SPI" is how the pico-sdk spells "function 1",
	 * since on the RP2040 all of the "function 1" functions are
	 * some part of SPI.)  */
	gpio_set_function(pin_clk,  GPIO_FUNC_SPI);
	gpio_set_function(pin_mosi, GPIO_FUNC_SPI);
	gpio_set_function(pin_miso, GPIO_FUNC_SPI);

	/* Initialize the CS pin for software control.  */
	gpio_init(pin_cs);
	gpio_set_dir(pin_cs, GPIO_OUT);
	gpio_put(pin_cs, 1);

	/* Initialize self.  */
	self->inst = inst;
	self->min_delay_ns = min_delay_ns;
	self->bogus_data = bogus_data;
	self->pin_cs = pin_cs;
	self->dead_until_ns = 0;
}

static void rp2040_hwspi_readwritev(struct rp2040_hwspi *self, const struct duplex_iovec *iov, int iovcnt) {
	assert(self);
	spi_inst_t *inst = self->inst;

	assert(inst);
	assert(iov);
	assert(iovcnt);

	uint64_t now = LO_CALL(bootclock, get_time_ns);
	if (now < self->dead_until_ns)
		sleep_until_ns(self->dead_until_ns);
	gpio_put(self->pin_cs, 0);
	/* TODO: Replace blocking reads+writes with DMA.  */
	for (int i = 0; i < iovcnt; i++) {
		if (iov[i].iov_write_src && iov[i].iov_read_dst)
			spi_write_read_blocking(inst, iov[i].iov_write_src, iov[i].iov_read_dst, iov[i].iov_len);
		else if (iov[i].iov_write_src)
			spi_write_blocking(inst, iov[i].iov_write_src, iov[i].iov_len);
		else if (iov[i].iov_read_dst)
			spi_read_blocking(inst, self->bogus_data, iov[i].iov_read_dst, iov[i].iov_len);
		else
			assert_notreached("duplex_iovec is neither read nor write");
	}
	gpio_put(self->pin_cs, 1);
	self->dead_until_ns = LO_CALL(bootclock, get_time_ns) + self->min_delay_ns;
}