Am335x SPI 驱动测试
内核版本：3.14.65
CPU：Am335x
1、编译内核：
make menuconfig
Device Drivers ->
<*>SPI support ->
<*>McSPI driver for omap
<*>User mode SPI device driver support
2、添加设备树
bb_spi0_pins: pinmux_bb_spi0_pins { pinctrl-single,pins = < 0x150 0x30 /* spi0_sclk.spi0_sclk, INPUT_PULLUP | MODE0 */ 0x154 0x30 /* spi0_d0.spi0_d0, INPUT_PULLUP | MODE0 */ 0x158 0x10 /* spi0_d1.spi0_d1, OUTPUT_PULLUP | MODE0 */ 0x15c 0x10 /* spi0_cs0.spi0_cs0, OUTPUT_PULLUP | MODE0 */ >; };
&spi0 {
#address-cells = <1>;
#size-cells = <0>;
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&bb_spi0_pins>;
channel@0 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "spidev";
reg = <0>;
spi-max-frequency = <16000000>;
spi-cpha;
};
channel@1 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "spidev";
reg = <1>;
spi-max-frequency = <16000000>;
};
};
编译内核和设备树，下载入开发板。
3、查看SPI是否被注册入Dev中：
ls /dev
console ram8 tty40 cpu_dma_latency ram9 tty41 full random tty42 hwrng root tty43 i2c-0 rtc0 tty44 input snd tty45 kmem spidev1.0 tty46 kmsg spidev1.1 tty47 log tty tty48 loop-control tty0 tty49
可以看到spidev已经被注册入设备中啦。
3、测试程序的编写：可以借鉴或者直接用Doucment/spi/spi_text.c下的文件。
/* * SPI testing utility (using spidev driver) * * Copyright (c) 2007 MontaVista Software, Inc. * Copyright (c) 2007 Anton Vorontsov <avorontsov@ru.mvista.com> * * 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. * * Cross-compile with cross-gcc -I/path/to/cross-kernel/include */ #include <stdint.h> #include <unistd.h> #include <stdio.h> #include <stdlib.h> #include <getopt.h> #include <fcntl.h> #include <sys/ioctl.h> #include <linux/types.h> #include <linux/spi/spidev.h> #define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0])) #define WREN 0x06 //set write enable Latch #define WRDI 0x04 // write disable #define RDSR 0x05 // read status register #define WRSR 0x01 // Write Status Register #define READ 0x03 // Read memory Data #define WRITE 0x02 // Write memory Data static void pabort(const char *s) { perror(s); abort(); } static const char *device = "/dev/spidev1.0"; static uint8_t mode; static uint8_t bits = 8; static uint32_t speed = 10000; static uint16_t delay; static void transfer_read(int fd) { int ret; uint8_t tx[] = { 0x03, 0x10, 0x00, }; uint8_t rx[6] = {0, }; struct spi_ioc_transfer tr[2] = { { .tx_buf = (unsigned long)tx, .rx_buf = (unsigned long)rx, .len = ARRAY_SIZE(tx), .delay_usecs = delay, .speed_hz = speed, .bits_per_word = bits, }, { .tx_buf = (unsigned long)tx, .rx_buf = (unsigned long)rx, .len = ARRAY_SIZE(rx), .delay_usecs = delay, .speed_hz = speed, .bits_per_word = bits, }, }; ret = ioctl(fd, SPI_IOC_MESSAGE(2), &tr); if (ret < 1) pabort("can't send spi message"); for (ret = 0; ret < ARRAY_SIZE(tx); ret++) { if (!(ret % 2)) puts(""); printf("%.5X ", rx[ret]); } puts(""); } static void transfer(int fd) { int ret; uint8_t tx[] = { 0x06, 0x02, 0x10, 0x00, 0xFF, 0xFF, 0x40, 0x00, 0x00, 0x00, 0x00, 0x95, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xDE, 0xAD, 0xBE, 0xEF, 0xBA, 0xAD, 0xF0, 0x0D, }; uint8_t rx[ARRAY_SIZE(tx)] = {0, }; struct spi_ioc_transfer tr = { .tx_buf = (unsigned long)tx, .rx_buf = (unsigned long)rx, .len = ARRAY_SIZE(tx), .delay_usecs = delay, .speed_hz = speed, .bits_per_word = bits, }; ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr); if (ret < 1) pabort("can't send spi message"); for (ret = 0; ret < ARRAY_SIZE(tx); ret++) { if (!(ret % 2)) puts(""); printf("%.5X ", rx[ret]); } puts(""); } static void print_usage(const char *prog) { printf("Usage: %s [-DsbdlHOLC3]\n", prog); puts(" -D --device device to use (default /dev/spidev1.1)\n" " -s --speed max speed (Hz)\n" " -d --delay delay (usec)\n" " -b --bpw bits per word \n" " -l --loop loopback\n" " -H --cpha clock phase\n" " -O --cpol clock polarity\n" " -L --lsb least significant bit first\n" " -C --cs-high chip select active high\n" " -3 --3wire SI/SO signals shared\n"); exit(1); } static void parse_opts(int argc, char *argv[]) { while (1) { static const struct option lopts[] = { { "device", 1, 0, 'D' }, { "speed", 1, 0, 's' }, { "delay", 1, 0, 'd' }, { "bpw", 1, 0, 'b' }, { "loop", 0, 0, 'l' }, { "cpha", 0, 0, 'H' }, { "cpol", 0, 0, 'O' }, { "lsb", 0, 0, 'L' }, { "cs-high", 0, 0, 'C' }, { "3wire", 0, 0, '3' }, { "no-cs", 0, 0, 'N' }, { "ready", 0, 0, 'R' }, { NULL, 0, 0, 0 }, }; int c; c = getopt_long(argc, argv, "D:s:d:b:lHOLC3NR", lopts, NULL); if (c == -1) break; switch (c) { case 'D': device = optarg; break; case 's': speed = atoi(optarg); break; case 'd': delay = atoi(optarg); break; case 'b': bits = atoi(optarg); break; case 'l': mode |= SPI_LOOP; break; case 'H': mode |= SPI_CPHA; break; case 'O': mode |= SPI_CPOL; break; case 'L': mode |= SPI_LSB_FIRST; break; case 'C': mode |= SPI_CS_HIGH; break; case '3': mode |= SPI_3WIRE; break; case 'N': mode |= SPI_NO_CS; break; case 'R': mode |= SPI_READY; break; default: print_usage(argv[0]); break; } } } int main(int argc, char *argv[]) { int ret = 0; int fd; parse_opts(argc, argv); fd = open(device, O_RDWR); if (fd < 0) pabort("can't open device"); //mode = mode | 0 | SPI_LSB_FIRST; /* * spi mode */ ret = ioctl(fd, SPI_IOC_WR_MODE, &mode); if (ret == -1) pabort("can't set spi mode"); ret = ioctl(fd, SPI_IOC_RD_MODE, &mode); if (ret == -1) pabort("can't get spi mode"); /* * bits per word */ ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits); if (ret == -1) pabort("can't set bits per word"); ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits); if (ret == -1) pabort("can't get bits per word"); /* * max speed hz */ ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed); if (ret == -1) pabort("can't set max speed hz"); ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed); if (ret == -1) pabort("can't get max speed hz"); printf("spi mode: %d\n", mode); printf("bits per word: %d\n", bits); printf("max speed: %d Hz (%d KHz)\n", speed, speed/1000); //transfer(fd); while(1) { //transfer(fd); transfer_read(fd); //write(fd,buf_me,1); } close(fd); return ret; }
需要注意:
是内核中SPI的数据发送和接收都是以byte为单位的。所以假如设置per_bits_word不是8or16or32时用上面的程序会出错的。假如设置的per_bits_word为9（https://blog.csdn.net/yasin_lee/article/details/54632982），那么在设置
struct spi_ioc_transfer tr 这个结构体时.len的长度一定要注意了。因为驱动在判断per_bits_word>8时，会用两个字节来存放要发送的数据的，大于16就会用4个字节来存放要发送的数据。
.len = ARRAY_SIZE(tx),ARRAY_SIZE只能计算tx数组的的元素的个数，并不会计算tx数组所占的字节数。所以当per_bits_word%8 > 时（也就是非8的整数倍），若是还用.len = ARRAY_SIZE(tx)
来计算SPI发送数据的长度，会引起内核崩溃的。
可以用以下方法来计算长度：
.len = sizeof(tx)，
.len = ARRAY_SIZE(tx)*2//（16>per_bits_word>8）
.len = ARRAY_SIZE(tx)*4//(32>per_bits_word>16)
根据测试在用这个函数发送数据时：
ioctl(fd, SPI_IOC_MESSAGE(1), &tr)
每配置一个 struct spi_ioc_transfer tr 结构体就相当于拉低一次CS，当然前提是配置CS低有效。
也就是SPI每发送一个SPI_IOC_MESSAGE,CS被拉低一次，可以通过这个来编写不同的SPI的接口芯片访问方式（暂时是这样理解的，等spi芯片到了，可以测试一下）。
还有就是此版本的SPI驱动并不支持低字节优先发送，假如设置了低字节优先发送的模式，会报以下错误：
spidev spi1.0: setup: unsupported mode bits 8 can't set spi mode: Invalid argument Aborted
可以从内核源码中了解相关信息：linux-3.14.65/drivers/spi/spi.c
* Note that this call will fail if the protocol driver specifies an option * that the underlying controller or its driver does not support. For * example, not all hardware supports wire transfers using nine bit words, * LSB-first wire encoding, or active-high chipselects. */ int spi_setup(struct spi_device *spi) { unsigned bad_bits, ugly_bits; int status = 0;
若是没有SPI芯片可以用来测试的话，可已将AM335x的Tx与Rx脚短接，这样也可以测试驱动及驱动测试程序的好坏。
