ARM-Linux s3c2440 UART Analysis (Part 2)-EEWORLD

Collect

This article is original from itspy. Please indicate the original source when copying/reprinting: http://blog.csdn.net/yyplc/article/details/7196290. Thank you!

Software (linux-2.6.30.4):

The serial port driver of the Linux system is different from the general character device. It adopts a hierarchical architecture and is implemented as a serial system.

(1) Focus on the low-level drivers of UART or other low-level serial hardware features.

(2) TTY driver that interfaces with the underlying driver.

(3) Processing the line discipline used to exchange data with the TTY driver.

The following figure describes the hierarchical relationship between serial systems (s3c2440 serial port implementation example), which can be summarized as: user application layer --> line planning layer --> TTY layer --> underlying driver layer --> physical hardware layer

Line discipline and TTY driver are independent of hardware platform, and the implementation is already provided in Linux source code, so for a specific platform, we only need to implement the underlying driver, which is what we care about most. In s3c2440a, it is mainly implemented by s3c2440.c and samsung.c in dirivers/serial/.

The Uart driver mainly revolves around three key data structures (defined in include/linux/serial_core.h):

UART specific driver structure definition: struct uart_driver s3c24xx_uart_drv;

UART port structure definition: struct uart_port s3c24xx_serial_ops;

UART related operation function structure definition: struct uart_ops s3c24xx_serial_ops;

Based on the above three structures, let's see how s3c2440 is connected to the serial port architecture in Linux:

The S3c2440 serial port related operation functions are defined in s3c24xx_serial_ops, which is a structuart_ops structure

static struct uart_ops s3c24xx_serial_ops ={
.pm =s3c24xx_serial_pm, //Power management function
.tx_empty = s3c24xx_serial_tx_empty, //Check if the transmit FIFO buffer is empty
.get_mctrl = s3c24xx_serial_get_mctrl, // Whether serial port flow control
.set_mctrl = s3c24xx_serial_set_mctrl, //Whether to set serial port flow control cts
.stop_tx =s3c24xx_serial_stop_tx, //stop sending
.start_tx =s3c24xx_serial_start_tx, //Start sending
.stop_rx =s3c24xx_serial_stop_rx, //stop receiving
.enable_ms = s3c24xx_serial_enable_ms, //empty function
.break_ctl = s3c24xx_serial_break_ctl, //Send break signal
.startup =s3c24xx_serial_startup, //Serial port sending/receiving, and interrupt request initial configuration function
.shutdown = s3c24xx_serial_shutdown, //Close the serial port
.set_termios = s3c24xx_serial_set_termios, //Serial port clk, baud rate, data bit and other parameter settings
.type = s3c24xx_serial_type, // CPU type about serial port
.release_port =s3c24xx_serial_release_port, //Release serial port
.request_port =s3c24xx_serial_request_port, //Request serial port
.config_port = s3c24xx_serial_config_port, //Some configuration information of the serial port info
.verify_port = s3c24xx_serial_verify_port, //serial port detection
};

Driver structure definition:

static struct uart_driver s3c24xx_uart_drv= {
.owner =THIS_MODULE,
.dev_name = "s3c2440_serial", //Specific device name
.nr =CONFIG_SERIAL_SAMSUNG_UARTS, //define how many ports there are
.cons = S3C24XX_SERIAL_CONSOLE, //console interface
.driver_name =S3C24XX_SERIAL_NAME, //Serial port name: ttySAC
.major =S3C24XX_SERIAL_MAJOR, //Major device number
.minor =S3C24XX_SERIAL_MINOR, //Minor device number
};

Port configuration structure definition, which includes a structuart_ports structure:

struct s3c24xx_uart_port {
unsignedchar rx_claimed;
unsignedchar tx_claimed;
unsignedint pm_level;
unsignedlong baudclk_rate;
unsignedint rx_irq;
unsignedint tx_irq;
structs3c24xx_uart_info *info;
structs3c24xx_uart_clksrc *clksrc;
structclk *clk;
structclk *baudclk;
structuart_port port;
#ifdef CONFIG_CPU_FREQ
structnotifier_block freq_transition;
#endif
};
static structs3c24xx_uart_ports3c24xx_serial_ports[CONFIG_SERIAL_SAMSUNG_UARTS] = {
[0]= { //Serial port 0
.port= {
.lock =__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[0].port.lock),
.iotype =UPIO_MEM, //
.irq =IRQ_S3CUART_RX0, //interrupt number
.uartclk = 0, //clock value
.fifosize = 16, //define FIFO buffer size
.ops = &s3c24xx_serial_ops, //Serial port related operation functions
.flags = UPF_BOOT_AUTOCONF,
.line = 0, //Line 1
}
},
[1]= {//Serial port 1
.port= {
.lock =__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[1].port.lock),
.iotype = UPIO_MEM,
.irq = IRQ_S3CUART_RX1,
.uartclk = 0,
.fifosize = 16,
.ops = &s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 1,
}
},
#if CONFIG_SERIAL_SAMSUNG_UARTS > 2
[2]= {//Serial port 2
.port= {
.lock =__SPIN_LOCK_UNLOCKED(s3c24xx_serial_ports[2].port.lock),
.iotype = UPIO_MEM,
.irq = IRQ_S3CUART_RX2,
.uartclk = 0,
.fifosize = 16,
.ops =&s3c24xx_serial_ops,
.flags = UPF_BOOT_AUTOCONF,
.line = 2,
}
},
#endif
};

To sum up, s3c2440 mainly implements these three data structures:

s3c24xx_serial_ops, s3c24xx_uart_drv, s3c24xx_uart_ports3c24xx_serial_ports

The next article will further explore the implementation of ARM-Linuxs3c2440 in combination with source code.

Keywords：ARM Linux s3c2440 UART Reference address：ARM-Linux s3c2440 UART Analysis (Part 2)

Previous article：ARM-Linux s3c2440 UART Analysis (Part 3)
Next article：ARM-Linux s3c2440 UART Analysis (I)

Recommended ReadingLatest update time:2024-11-16 15:29

S3C2440-SDRAM connection analysis

A relatively detailed analysis of the connections between S3C2440 and SDRAM, Nandflash, and Norflash. Analysis of the address connection between S3C2440 and SDRAM S3C2440 has 27 address lines ADDR and 8 chip select signals ngcs0-ngcs7, corresponding to bank0-bank7. When accessing the address space of bankx, the

[Microcontroller]

S3C2440 interrupt control register

1. SUBSRCPND register (SUB SOURCE PENDING) The SUBSRCPND register is used to identify whether interrupts such as INT_RXD0, INT_TXD0 (there are 11 such interrupts in S3C2410 and 15 in S3C2440) have occurred, and each bit corresponds to an interrupt. When these interrupts occur and are not masked by the INTSUBMSK regist

[Microcontroller]

Talk about the use of ARM NEON SIMD architecture extensions in Zynq SoC

Inside all Zynq All Programmable SoCs, you'll find a dual-core ARM Cortex-A9 MPCore processor, and both processors in the Zynq SoC feature the ARM NEON SIMD architecture extensions. So why would you want to use the ARM NEON SIMD extensions? Because you can get a significant performance boost for your software. You may

[Microcontroller]

Talk about the use of ARM NEON SIMD architecture extensions in Zynq SoC

ARM startup and working mode switching

In the ARM system, there are usually three ways to control the execution flow of the program: During normal program execution, the value of the program counter register (PC) increases by 4 bytes for each ARM instruction executed; the value of the program counter register (PC) increases by 2 bytes for each Thumb inst

[Microcontroller]

ARM LCD and LCD controller

Since we mentioned LCD, the first thing we must understand is its types. CD (liquid crystal display) is a display that uses liquid crystal to control transmittance counting to achieve color. Compared with traditional CRT displays, it has many advantages: light and thin, low energy consumption, low radiation, etc., and

[Microcontroller]

【ARM】s3c2440 gpio button control

Function Through GPIO, key 1 lights up LED 1, key 2 lights up LED 2... illustrate 1) Because the 2440 keys only involve rows, scanning keys is much simpler than the 2410 2) Before performing a shift operation, the data register must be initialized, otherwise an error will occur (hardware characteristics) Source

[Microcontroller]

Design of multifunctional integrated communication control system based on ARM9

With the rapid development of computer technology, industrial data acquisition has evolved from traditional measurement and control circuits to modern data acquisition and control systems consisting of microcomputers, interface circuits, external general equipment, and industrial production objects. However, data a

[Microcontroller]

Design of multifunctional integrated communication control system based on ARM9

Learn ARM development(14)

Since it is still troublesome to develop under LINUX, is there a more convenient and simple development method under WINDOWS? The answer is yes. Of course, we cannot choose a development tool like ADS, because it is too expensive. Even if we use pirated software, we will not feel at ease, so we have to adopt other s

[Microcontroller]

Popular Resources
Popular amplifiers