/* * linux/arch/arm/mach-davinci/serial.c * * TI DaVinci serial driver hookup file * * Copyright (C) 2006 Texas Instruments. * * ---------------------------------------------------------------------------- * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. * ---------------------------------------------------------------------------- * */
#include <linux/config.h> #include <linux/module.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/serial_8250.h> #include <linux/serial_reg.h> #include <linux/delay.h>
#include <asm/io.h> #include <asm/irq.h> #include <asm/hardware.h> #include <asm/hardware/clock.h> #include <asm/serial.h> #include <asm/arch/hardware.h> #include <asm/arch/irqs.h> #include <asm/arch/cpu.h>
#define UART_DAVINCI_PWREMU 0x0c
/* 对于DM644x平台来说,该文件的作用只是打开串口0模块的时钟和电源。 DM644x平台的串口采用的是TL16C550工业标准异步通信模块。内核中已经包含 该标准((8250/16550))串口的驱动的代码:drivers/serial/8250.c。
*/
// 从串口寄存器offset读出值
static inline unsigned int davinci_serial_in(struct plat_serial8250_port *up, int offset) { offset <<= up->regshift; return (unsigned int)__raw_readb(up->membase + offset); }
// 向串口寄存器offset写入值value
static inline void davinci_serial_outp(struct plat_serial8250_port *p, int offset, int value) { offset <<= p->regshift; __raw_writeb(value, p->membase + offset); }
// 复位串口。UART_DAVINCI_PWREMU寄存器是达芬奇平台专有的,通用的8250串口没有。
static void __init davinci_serial_reset(struct plat_serial8250_port *p) { /* reset both transmitter and receiver: bits 14,13 = UTRST, URRST */ unsigned int pwremu = 0;
davinci_serial_outp(p, UART_IER, 0); /* disable all interrupts */
davinci_serial_outp(p, UART_DAVINCI_PWREMU, pwremu);// 禁止发送和接收,停止UART
mdelay(10);
pwremu |= (0x3 << 13); pwremu |= 0x1; // 打开接收和发送,启动UART
davinci_serial_outp(p, UART_DAVINCI_PWREMU, pwremu); }
#define UART_DM6467_SCR __REG(DAVINCI_UART0_BASE + 0x40) /* * Internal UARTs need to be initialized for the 8250 autoconfig to work * properly. Note that the TX watermark initialization may not be needed * once the 8250.c watermark handling code is merged. */ static int __init dm646x_serial_reset(void) { UART_DM6467_SCR = 0x08;
return 0; }
/* 串口初始化,打开时钟和电源。 davinci_serial_init()例程由board_evm.c中的board_init()例程调用,后者被 davinci_map_io()例程调用,而其又被注册到board_evm.c中的机器描述符中(struct machine_desc), 故具体调用过程是: start_kernel()-->setup_arch()-->paging_init()-->mdesc->map_io() (其就是davinci_map_io())-->board_init()-->davinci_serial_init()。 */ void __init davinci_serial_init(struct platform_device *pdev) { struct clk *uart_clk; struct device *dev = &pdev->dev; struct plat_serial8250_port *p; int uart; char uart_name[6];
memset(uart_name, 0, sizeof(uart_name)); for (p = dev->platform_data; p && p->flags; p++) { switch (p->mapbase) {// 获取串口号
case DAVINCI_UART0_BASE: uart = 0; break; case DAVINCI_UART1_BASE: uart = 1; break; case DM644X_UART2_BASE: case DM355_UART2_BASE: uart = 2; break; default: dev_err(dev, "Unknown UART base address 0x%08lx\n", p->mapbase); continue; } sprintf(uart_name, "UART%i", uart); uart_clk = clk_get(dev, uart_name);// 获取时钟
if (IS_ERR(uart_clk)) dev_err(dev, "failed to get %s clock\n", uart_name); else clk_enable(uart_clk); // 打开时钟和电源
// 如果是DM355平台,则复位
if (cpu_is_davinci_dm355()) davinci_serial_reset(p); } }
late_initcall(dm646x_serial_reset);
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