core/drivers/hi16xx_uart.c

// SPDX-License-Identifier: BSD-2-Clause
/*
 * Copyright (c) 2016, Linaro Limited
 */
#include <assert.h>
#include <drivers/hi16xx_uart.h>
#include <io.h>
#include <keep.h>
#include <mm/core_mmu.h>
#include <util.h>

/* Register offsets */

#define UART_RBR	0x00	/* RX data buffer register */
#define UART_THR	0x00	/* TX data buffer register */
#define UART_DLL	0x00	/* Lower-bit frequency divider register */

#define UART_IEL	0x04	/* Interrupt enable register */
#define UART_DLH	0x04	/* Upper-bit frequency divider register */

#define UART_FCR	0x08	/* FIFO control register */

#define UART_LCR	0x0C	/* Line control register */

#define UART_LSR	0x14	/* Line status register */

#define UART_USR	0x7C	/* Status register */

/*
 * Line control register
 */

/* Data length selection */
#define UART_LCR_DLS5	0x0	/* 5 bits */
#define UART_LCR_DLS6	0x1	/* 6 bits */
#define UART_LCR_DLS7	0x2	/* 7 bits */
#define UART_LCR_DLS8	0x3	/* 8 bits */

/* Enable access to UART_DLL and UART_DLH */
#define UART_LCR_DLAB	0x80

/*
 * FIFO control register
 */

#define UART_FCR_FIFO_EN	0x1	/* Enable FIFO (depth: 32 bytes) */
#define UART_FCR_RX_FIFO_RST	0x2	/* Clear receive FIFO (auto reset) */
#define UART_FCR_TX_FIFO_RST	0x4	/* Clear send FIFO (auto reset) */


/*
 * Status register
 */

#define UART_USR_BUSY_BIT	0	/* 0: idle/non-activated, 1: busy */
#define UART_USR_TFNF_BIT	1	/* Transmit FIFO not full bit */
#define UART_USR_TFE_BIT	2	/* Transmit FIFO empty bit */
#define UART_USR_RFNE_BIT	3	/* Receive FIFO not empty bit */
#define UART_USR_RFF_BIT	4	/* Receive FIFO full bit */

static vaddr_t chip_to_base(struct serial_chip *chip)
{
	struct hi16xx_uart_data *pd =
		container_of(chip, struct hi16xx_uart_data, chip);

	return io_pa_or_va(&pd->base);
}

static void hi16xx_uart_flush(struct serial_chip *chip)
{
	vaddr_t base = chip_to_base(chip);

	while (!(io_read32(base + UART_USR) & UART_USR_TFE_BIT))
		;
}

static void hi16xx_uart_putc(struct serial_chip *chip, int ch)
{
	vaddr_t base = chip_to_base(chip);

	/* Wait until TX FIFO is empty */
	while (!(io_read32(base + UART_USR) & UART_USR_TFE_BIT))
		;

	/* Put character into TX FIFO */
	io_write32(base + UART_THR, ch & 0xFF);
}

static bool hi16xx_uart_have_rx_data(struct serial_chip *chip)
{
	vaddr_t base = chip_to_base(chip);

	return (io_read32(base + UART_USR) & UART_USR_RFNE_BIT);
}

static int hi16xx_uart_getchar(struct serial_chip *chip)
{
	vaddr_t base = chip_to_base(chip);

	while (!hi16xx_uart_have_rx_data(chip))
		;
	return io_read32(base + UART_RBR) & 0xFF;
}

static const struct serial_ops hi16xx_uart_ops = {
	.flush = hi16xx_uart_flush,
	.getchar = hi16xx_uart_getchar,
	.have_rx_data = hi16xx_uart_have_rx_data,
	.putc = hi16xx_uart_putc,
};
KEEP_PAGER(hi16xx_uart_ops);

void hi16xx_uart_init(struct hi16xx_uart_data *pd, paddr_t base,
		      uint32_t uart_clk, uint32_t baud_rate)
{
	uint16_t freq_div = uart_clk / (16 * baud_rate);

	pd->base.pa = base;
	pd->chip.ops = &hi16xx_uart_ops;

	/* Enable (and clear) FIFOs */
	io_write32(base + UART_FCR, UART_FCR_FIFO_EN);

	/* Enable access to _DLL and _DLH */
	io_write32(base + UART_LCR, UART_LCR_DLAB);

	/* Calculate and set UART_DLL */
	io_write32(base + UART_DLL, freq_div & 0xFF);

	/* Calculate and set UART_DLH */
	io_write32(base + UART_DLH, (freq_div >> 8) & 0xFF);

	/* Clear _DLL/_DLH access bit, set data size (8 bits), parity etc. */
	io_write32(base + UART_LCR, UART_LCR_DLS8);

	/* Disable interrupt mode */
	io_write32(base + UART_IEL, 0);

	hi16xx_uart_flush(&pd->chip);
}