src/soc/nvidia/tegra124/uart.c

/* SPDX-License-Identifier: GPL-2.0-only */

#include <device/mmio.h>
#include <boot/coreboot_tables.h>
#include <console/uart.h>
#include <drivers/uart/uart8250reg.h>

struct tegra124_uart {
	union {
		uint32_t thr; // Transmit holding register.
		uint32_t rbr; // Receive buffer register.
		uint32_t dll; // Divisor latch lsb.
	};
	union {
		uint32_t ier; // Interrupt enable register.
		uint32_t dlm; // Divisor latch msb.
	};
	union {
		uint32_t iir; // Interrupt identification register.
		uint32_t fcr; // FIFO control register.
	};
	uint32_t lcr; // Line control register.
	uint32_t mcr; // Modem control register.
	uint32_t lsr; // Line status register.
	uint32_t msr; // Modem status register.
} __packed;

static void tegra124_uart_tx_flush(struct tegra124_uart *uart_ptr);
static int tegra124_uart_tst_byte(struct tegra124_uart *uart_ptr);

static void tegra124_uart_init(struct tegra124_uart *uart_ptr)
{
	// Use a hardcoded divisor for now.
	const unsigned int divisor = 221;
	const uint8_t line_config = UART8250_LCR_WLS_8; // 8n1

	tegra124_uart_tx_flush(uart_ptr);

	// Disable interrupts.
	write8(&uart_ptr->ier, 0);
	// Force DTR and RTS to high.
	write8(&uart_ptr->mcr, UART8250_MCR_DTR | UART8250_MCR_RTS);
	// Set line configuration, access divisor latches.
	write8(&uart_ptr->lcr, UART8250_LCR_DLAB | line_config);
	// Set the divisor.
	write8(&uart_ptr->dll, divisor & 0xff);
	write8(&uart_ptr->dlm, (divisor >> 8) & 0xff);
	// Hide the divisor latches.
	write8(&uart_ptr->lcr, line_config);
	// Enable FIFOs, and clear receive and transmit.
	write8(&uart_ptr->fcr, UART8250_FCR_FIFO_EN |
	       UART8250_FCR_CLEAR_RCVR | UART8250_FCR_CLEAR_XMIT);
}

static unsigned char tegra124_uart_rx_byte(struct tegra124_uart *uart_ptr)
{
	if (!tegra124_uart_tst_byte(uart_ptr))
		return 0;
	return read8(&uart_ptr->rbr);
}

static void tegra124_uart_tx_byte(struct tegra124_uart *uart_ptr, unsigned char data)
{
	while (!(read8(&uart_ptr->lsr) & UART8250_LSR_THRE));
	write8(&uart_ptr->thr, data);
}

static void tegra124_uart_tx_flush(struct tegra124_uart *uart_ptr)
{
	while (!(read8(&uart_ptr->lsr) & UART8250_LSR_TEMT));
}

static int tegra124_uart_tst_byte(struct tegra124_uart *uart_ptr)
{
	return (read8(&uart_ptr->lsr) & UART8250_LSR_DR) == UART8250_LSR_DR;
}

uintptr_t uart_platform_base(unsigned int idx)
{
	//Default to UART A
	unsigned int base = 0x70006000;
	//UARTs A - E are mapped as index 0 - 4
	if ((idx < 5)) {
		if (idx != 1) { //not UART B
			base += idx * 0x100;
		} else {
			base += 0x40;
		}
	}
	return base;
}

void uart_init(unsigned int idx)
{
	struct tegra124_uart *uart_ptr = uart_platform_baseptr(idx);
	tegra124_uart_init(uart_ptr);
}

unsigned char uart_rx_byte(unsigned int idx)
{
	struct tegra124_uart *uart_ptr = uart_platform_baseptr(idx);
	return tegra124_uart_rx_byte(uart_ptr);
}

void uart_tx_byte(unsigned int idx, unsigned char data)
{
	struct tegra124_uart *uart_ptr = uart_platform_baseptr(idx);
	tegra124_uart_tx_byte(uart_ptr, data);
}

void uart_tx_flush(unsigned int idx)
{
	struct tegra124_uart *uart_ptr = uart_platform_baseptr(idx);
	tegra124_uart_tx_flush(uart_ptr);
}

enum cb_err fill_lb_serial(struct lb_serial *serial)
{
	serial->type = LB_SERIAL_TYPE_MEMORY_MAPPED;
	serial->baseaddr = uart_platform_base(CONFIG_UART_FOR_CONSOLE);
	serial->baud = get_uart_baudrate();
	serial->regwidth = 4;
	serial->input_hertz = uart_platform_refclk();

	return CB_SUCCESS;
}