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/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
/* UART module for Chrome EC */
#include <stdarg.h>
#include "board.h"
#include "console.h"
#include "gpio.h"
#include "lpc.h"
#include "registers.h"
#include "task.h"
#include "uart.h"
#include "util.h"
/* Baud rate for UARTs */
#define BAUD_RATE 115200
void uart_tx_start(void)
{
/* Re-enable the transmit interrupt, then forcibly trigger the
* interrupt. This works around a hardware problem with the
* UART where the FIFO only triggers the interrupt when its
* threshold is _crossed_, not just met. */
LM4_UART_IM(0) |= 0x20;
task_trigger_irq(LM4_IRQ_UART0);
}
void uart_tx_stop(void)
{
LM4_UART_IM(0) &= ~0x20;
}
int uart_tx_stopped(void)
{
return !(LM4_UART_IM(0) & 0x20);
}
void uart_tx_flush(void)
{
/* Wait for transmit FIFO empty */
while (!(LM4_UART_FR(0) & 0x80))
;
}
int uart_tx_ready(void)
{
return !(LM4_UART_FR(0) & 0x20);
}
int uart_rx_available(void)
{
return !(LM4_UART_FR(0) & 0x10);
}
void uart_write_char(char c)
{
LM4_UART_DR(0) = c;
}
int uart_read_char(void)
{
return LM4_UART_DR(0);
}
void uart_disable_interrupt(void)
{
task_disable_irq(LM4_IRQ_UART0);
}
void uart_enable_interrupt(void)
{
task_enable_irq(LM4_IRQ_UART0);
}
/* Interrupt handler for UART0 */
static void uart_0_interrupt(void)
{
/* Clear transmit and receive interrupt status */
LM4_UART_ICR(0) = 0x70;
/* Read input FIFO until empty, then fill output FIFO */
uart_process();
}
DECLARE_IRQ(LM4_IRQ_UART0, uart_0_interrupt, 1);
/* Interrupt handler for UART1 */
static void uart_1_interrupt(void)
{
/* Clear transmit and receive interrupt status */
LM4_UART_ICR(1) = 0x70;
/* TODO: (crosbug.com/p/7488) handle input */
/* If we have space in our FIFO and a character is pending in LPC,
* handle that character. */
if (!(LM4_UART_FR(1) & 0x20) && lpc_comx_has_char()) {
/* Copy the next byte then disable transmit interrupt */
LM4_UART_DR(1) = lpc_comx_get_char();
LM4_UART_IM(1) &= ~0x20;
}
/* Handle received character. There is no flow control on input;
* received characters are blindly forwarded to LPC. This is ok
* because LPC is much faster than UART, and we don't have flow control
* on the UART receive-side either. */
if (!(LM4_UART_FR(1) & 0x10))
lpc_comx_put_char(LM4_UART_DR(1));
}
/* Must be same prio as LPC interrupt handler so they don't preempt */
DECLARE_IRQ(LM4_IRQ_UART1, uart_1_interrupt, 2);
/* Configure GPIOs for the UART module. */
static void configure_gpio(void)
{
#ifdef BOARD_link
/* UART0 RX and TX are GPIO PA0:1 alternate function 1 */
gpio_set_alternate_function(LM4_GPIO_A, 0x03, 1);
/* UART1 RX and TX are GPIO PC4:5 alternate function 2 */
gpio_set_alternate_function(LM4_GPIO_C, 0x30, 2);
#else
/* UART0 RX and TX are GPIO PA0:1 alternate function 1 */
gpio_set_alternate_function(LM4_GPIO_A, 0x03, 1);
/* UART1 RX and TX are GPIO PB0:1 alternate function 1*/
gpio_set_alternate_function(LM4_GPIO_B, 0x03, 1);
#endif
}
int uart_init(void)
{
volatile uint32_t scratch __attribute__((unused));
int ch;
/*
* Check that the UART parameters used for panic/watchdog are matching
* the UART0 parameters.
*/
BUILD_ASSERT(LM4_UART_CH0_BASE == CONFIG_UART_ADDRESS);
/* Enable UART0 and UART1 and delay a few clocks */
LM4_SYSTEM_RCGCUART |= 0x03;
scratch = LM4_SYSTEM_RCGCUART;
/* Configure GPIOs */
configure_gpio();
/* Configure UART0 and UART1 (identically) */
for (ch = 0; ch < 2; ch++) {
/* Disable the port */
LM4_UART_CTL(ch) = 0x0300;
/* Set the baud rate divisor */
LM4_UART_IBRD(ch) = (CPU_CLOCK / 16) / BAUD_RATE;
LM4_UART_FBRD(ch) =
(((CPU_CLOCK / 16) % BAUD_RATE) * 64 + BAUD_RATE / 2) /
BAUD_RATE;
/* 8-N-1, FIFO enabled. Must be done after setting
* the divisor for the new divisor to take effect. */
LM4_UART_LCRH(ch) = 0x70;
/* Interrupt when RX fifo at minimum (>= 1/8 full), and TX fifo
* when <= 1/4 full */
LM4_UART_IFLS(ch) = 0x01;
/* Unmask receive-FIFO, receive-timeout. We need
* receive-timeout because the minimum RX FIFO depth is 1/8 = 2
* bytes; without the receive-timeout we'd never be notified
* about single received characters. */
LM4_UART_IM(ch) = 0x50;
/* Enable the port */
LM4_UART_CTL(ch) |= 0x0001;
}
/* Enable interrupts */
task_enable_irq(LM4_IRQ_UART0);
task_enable_irq(LM4_IRQ_UART1);
/* Print hello on UART1 for debugging */
/* TODO: remove in production */
{
const char *c = "Hello on UART1\r\n";
while (*c)
uart_comx_putc(*c++);
}
return EC_SUCCESS;
}
/*****************************************************************************/
/* COMx functions */
int uart_comx_putc_ok(void)
{
if (LM4_UART_FR(1) & 0x20) {
/* FIFO is full, so enable transmit interrupt to let us know
* when it empties. */
LM4_UART_IM(1) |= 0x20;
return 0;
} else {
return 1;
}
}
void uart_comx_putc(int c)
{
LM4_UART_DR(1) = c;
}
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