This article walks through writing a simple device driver as well as adding the FPGA register.
For related subjects, please refer to the SOC Table of Contents.
We will first create a folder titled “work” in our home folder and go into its directory from the terminal.
We will next execute the following two commands to create a new PetaLinux project in the directory.
sptl
petalinux-create -t project --template zynq -n fii-module
Note that we named the project fii-module to match the development board we will be using.
We will then copy the FPGA SDK directory FII_7030.sdk to the work folder we just created and edit fii_module. Use the following command to enter the fii_module project directory:
cd fii-module
Next, we will execute the sptl command, and configure the project by using the following command:
petalinux-config --get-hw-description ~/work/FII_7030.sdk/
We don’t need to make any changes, and we can simply choose < Save > and < Exit >.
Next, we will insert and create the fpga device tree driver by using the following command:
petalinux-create -t modules --name fii-driver
We can now go on to edit the driver by going into the ~/work/fii-module/project-spec/meta-user/recipes-modules/fii-driver/files directory and editing the fii-driver.c file.
Driver Code Download: Simple Character Device Driver
Once the file is open, we will modify it as such:
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/uaccess.h> /* for put_user */
#include <asm/errno.h>
#include <linux/io.h>
#include <linux/of.h>
#include <linux/of_device.h>
//#include <linix/of_platform.h>
/*
0x43c0_0000 + 4 = value
0x43c0_0000 + 8 = direction
*/
#define DEVICE_NAME "fii-module"
#define CLASS_NAME "fii-module_class"
static int major;
static struct class *swled_class;
static unsigned int *gpio_data;
static unsigned int *gpio_dir ;
static int swled_open(struct inode* node,struct file* filp){
unsigned int gpio_base = (0x43c00000);
gpio_data = ioremap(gpio_base,8);
if(gpio_data){
printk("kernel: ioremap(0x%08x)=0x%08x \n",gpio_base,gpio_data);
}
else{
return -EINVAL;
}
gpio_dir = gpio_data + 1;
printk("kernel: gpio_data address = 0x%08x \n", gpio_data);
printk("kernel: gpio_dir address = 0x%08x \n", gpio_dir);
return 0;
}
int swled_release(struct inode *inode, struct file *filp)
{
// MOD_DEC_USE_COUNT;
iounmap(gpio_data);
return 0;
}
/*
0x43c0_0000 + 0 = value
0x43c0_0000 + 4 = direction
*/
static ssize_t swled_read(struct file *filp, char *buf, size_t size, loff_t *offset)
{
unsigned char val[32];
unsigned int temp;
unsigned int *addr_p;
int i = 0, cnt;
printk("kernel: swled_read start.... size = %d\n", size);
cnt = size;
addr_p = gpio_data;
temp = *addr_p ;
for(i = 0; i < cnt/4; i++ )
{
val[i*4 + 3] = temp & 0xff;
val[i*4 + 2] = (temp >> 8) & 0xff;
val[i*4 + 1] = (temp >> 16) & 0xff;
val[i*4 + 0] = (temp >> 24) & 0xff;
addr_p ++;
temp = *addr_p;
}
if(i % 4 == 1)
{
val[i*4 + 0] = temp & 0xff;
}
if(i % 4 == 2)
{
val[i*4 + 1] = temp & 0xff;
val[i*4 + 0] = (temp >> 8) & 0xff;
}
if(i % 4 == 3)
{
val[i*4 + 2] = temp & 0xff;
val[i*4 + 1] = (temp >> 8) & 0xff;
val[i*4 + 0] = (temp >> 16) & 0xff;
}
copy_to_user(buf, val, cnt);
return cnt;
}
static ssize_t swled_write(struct file * filp, const char __user *buf, size_t size, loff_t * offset) {
unsigned char val[32];
unsigned int temp = 0;
unsigned int * addr_p;
int i,cnt;
memset(val,0,32);
addr_p = gpio_data;
printk("kernel: swled_write start.... size = %d\n", size);
copy_from_user(&val, buf, size);
cnt = size - 1;
printk("kernel: val[0] = 0x%08x \n", val[0]);
if(val[0] == 'w')
{
temp = val[2];
temp = temp << 8 | val[3];
temp = temp << 8 | val[4];
temp = temp << 8 | val[5];
*addr_p = temp;
printk("kernel: gpio_data = 0x%08x \n", temp);
}
else if(val[0] == 'd')
{
addr_p ++;
temp = val[2];
temp = temp << 8 | val[3];
temp = temp << 8 | val[4];
temp = temp << 8 | val[5];
*addr_p = temp;
printk("kernel: gpio_dir = 0x%08x \n", temp);
}
else
{
printk("kernel: invalid parameter \n");
}
return size;
}
static struct file_operations swled_oprs = {
.owner = THIS_MODULE,
.open = swled_open,
.write = swled_write,
.read = swled_read,
.release= swled_release,
};
static int swled_init(void){ /* register device */
/*
*
* int register_chrdev (unsigned int major,
* const char *name,
* struct file_operations*fops);
*
* major => 0, automatic mode; others major device ID
*/
major=register_chrdev(0, DEVICE_NAME, &swled_oprs);
if (major < 0) {
printk ("Registering the character device failed with %d\n", major);
return major;
}
swled_class = class_create(THIS_MODULE, CLASS_NAME);
device_create(swled_class, NULL, MKDEV(major,0), NULL, DEVICE_NAME);
return 0;
}
static void swled_exit(void){
unregister_chrdev(major, DEVICE_NAME);
device_destroy(swled_class,MKDEV(major,0));
class_destroy(swled_class);
};
module_init(swled_init);
module_exit(swled_exit);
MODULE_LICENSE("GPL");
When you finish writing the code, please execute the following command to edit the PetaLinux driver settings.
petalinux-config -c rootfs
Once the graphical interface opens, go into modules and include fii-driver by pressing [Y]. Make sure you save and exit when you are finished.
We will then proceed to compile the core by using the following command:
petalinux-build -c kernel
Next, we will use the following command to compile the driver:
petalinux-build -c fii-driver
Now we can go ahead and compile the entire project by using the following command:
petalinux-build
We will now create the project files by executing the following command:
petalinux-package --boot --fsbl ./images/linux/zynq_fsbl.elf --fpga --u-boot --force
We will now copy the BOOT.BIN file and the image.ub file from ~/work/fii-module/images/linux/ to partition 1 of the SD card, which should be the boot partition; and extract rootfs.cpio to the other partition, which should be titled rootfs.
We will also copy the file at ~/work/fii_module/build/tmp/sysroots-components/plnx_zynq7/fii-driver/lib/modules/4.14.0-xilinx-v2018.3/extra/fii-driver.ko to the SD card.
When finished, please plug the SD card into the fii_7030 development board and boot it up. Make sure you are connected to the board via PuTTY. Recall that both the username and the password is root.
