DTS syntax and interrupts from PL under Linux

A DTS tutorial was just posted by the Xillinux people.  It might be helpful.

http://www.zedboard.org/node/529

Bryan

The following entry can be made to the DTS to add an AXI Timer with an interrupt attached to it.  This will attach interrupt 84 in XPS to the GIC.  84 was the number that XPS assigned when I connected the interrupt.  You have to subtract 32 from that number.

ttmytimer {
tttcompatible = "dglnt,mytimer-1.00.a";
tttinterrupt-parent = <&ps7_scugic_0>;
tttinterrupts = < 0 52 4 >;
tttreg = <0x42800000 0x10000>;
tt};


You can then add the following code to the probe function of the device driver.


t/* Register the interrupt */
tirq = platform_get_irq(pdev, 0);
tif (irq >= 0) {
ttreturnVal = request_irq(irq, timer_irq_handler, 0, pdev->name, pdev);
ttif (returnVal != 0) {
tttdev_info(&pdev->dev, "Interrupt Registered.
");
tttgoto err_irq;
tt}
t}


t// Configure Interrupt Rate
tiowrite32( SECOND_1,
tt   base_addr + 1);

tregVal = ioread32(base_addr + 1);
tdev_info(&pdev->dev, "Loaded with value of %d
", regVal);

t/* Turn on the timer */
tiowrite32( TCSR_EINT_M |
tt   TCSR_ENT_M  |
                   TCSR_ARHT_M |
tt   TCSR_MODE_GEN_M |
                   TCSR_UDT_DOWN_M,
tt   base_addr);


Then you need to fill in the handler for the IRQ

static irqreturn_t timer_irq_handler(int irq, void *dev_id)
{
tstruct platform_device *pdev = dev_id;
tu32 regVal;

tdev_info(&pdev->dev, "ECE453 PL Timer IRQ received.
");
tregVal =ioread32(base_addr);
tdev_info(&pdev->dev, "ECE453 Control Value: 0x%08x
", regVal);
tregVal =ioread32(base_addr+1);
tdev_info(&pdev->dev, "ECE453 LoadValue: %d
", regVal);
t
tregVal =ioread32(base_addr);
tregVal |= TCSR_INT_M ;
tiowrite32( regVal ,
tt   base_addr);

treturn IRQ_HANDLED;
}

The following entry can be made to the DTS to add an AXI Timer with an interrupt attached to it.  This will attach interrupt 84 in XPS to the GIC.  84 was the number that XPS assigned when I connected the interrupt.  You have to subtract 32 from that number.

ttmytimer {
tttcompatible = "dglnt,mytimer-1.00.a";
tttinterrupt-parent = <&ps7_scugic_0>;
tttinterrupts = < 0 52 4 >;
tttreg = <0x42800000 0x10000>;
tt};


You can then add the following code to the probe function of the device driver.


t/* Register the interrupt */
tirq = platform_get_irq(pdev, 0);
tif (irq >= 0) {
ttreturnVal = request_irq(irq, timer_irq_handler, 0, pdev->name, pdev);
ttif (returnVal != 0) {
tttdev_info(&pdev->dev, "Interrupt Registered.
");
tttgoto err_irq;
tt}
t}


t// Configure Interrupt Rate
tiowrite32( SECOND_1,
tt   base_addr + 1);

tregVal = ioread32(base_addr + 1);
tdev_info(&pdev->dev, "Loaded with value of %d
", regVal);

t/* Turn on the timer */
tiowrite32( TCSR_EINT_M |
tt   TCSR_ENT_M  |
                   TCSR_ARHT_M |
tt   TCSR_MODE_GEN_M |
                   TCSR_UDT_DOWN_M,
tt   base_addr);


Then you need to fill in the handler for the IRQ

static irqreturn_t timer_irq_handler(int irq, void *dev_id)
{
tstruct platform_device *pdev = dev_id;
tu32 regVal;

tdev_info(&pdev->dev, "ECE453 PL Timer IRQ received.
");
tregVal =ioread32(base_addr);
tdev_info(&pdev->dev, "ECE453 Control Value: 0x%08x
", regVal);
tregVal =ioread32(base_addr+1);
tdev_info(&pdev->dev, "ECE453 LoadValue: %d
", regVal);
t
tregVal =ioread32(base_addr);
tregVal |= TCSR_INT_M ;
tiowrite32( regVal ,
tt   base_addr);

treturn IRQ_HANDLED;
}

Hi dear,
we are also doing similar kind of this. we are using zedboard. In FPGA we are generating interrupt on line 91 and in arm under linux we are trying to catch the interrupt.

for this i have written a kernel module to catch the interrupt. in this module, interrupt on line 91 is properly getting registered. but unfortunately i am not getting any print messages in irq_handler.

the following is my module code:

#include <linux/module.h>    /* Needed by all linux kernel driver modules */
#include <linux/kernel.h>    /* Needed for KERN_INFO */
#include <linux/cdev.h>        /* provides cdev struct, how the kernel represents char devices internally */

// just sorta added:
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/irq.h>
#include <linux/of.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/interrupt.h>
#include <asm/io.h>


#define MAJOR_NUM 35
#define DEVICE_NAME "gpio"

static int irq;  // the virtual irq number that will be requested from open firmware
// static test_hw_map *module_register;
static struct cdev timer_intr_cdev;

/* IRQ HANDLER */
static irqreturn_t timer_intr_irq_handler(int irq, void *dev_id) {
    printk(KERN_ERR "printk err timer_intr - in the irq handler!
");
    pr_err("pr_err timer_intr - in the irq handler!
");
    return IRQ_HANDLED;
}


/* FILE SYSTEM OPERATIONS */
static int timer_intr_open(struct inode *inode, struct file *file) {
    printk(KERN_INFO "timer_intr_open: successful
");
    return 0;
}
struct file_operations timer_intr_fops = {
    .open  =    timer_intr_open,
};

/* LOADING/UNLOADING DRIVER FUNCTIONS */
/* init function is run when driver is added to kernel */
static int __init timer_intr_init(void) {
    struct irq_data *data;t
    struct device_node *np = NULL;
    int result, hw_irq;
    struct resource resource;

    unsigned long *virt_addr;
    unsigned int startAddr;

    // check how to get output
    printk(KERN_INFO "timer_intr init
");
   
    np = of_find_node_by_name(NULL, "gpio");
    if (!np) {
        printk(KERN_ERR "gpio: can't find compatible node in this kernel build");
        return -ENODEV;
    } else {
        result = of_address_to_resource(np, 0, &resource);
        if (result < 0) {
            return result;
        }
        printk(KERN_INFO "gpio: reg. size=%d Bytes
", (u32)resource.end - (u32)resource.start);
        startAddr = (unsigned int)resource.start;
       
        // get a virtual irq number from device resource struct
        irq = of_irq_to_resource(np, 0, &resource);
        if (irq == NO_IRQ) {
            printk(KERN_ERR "gpio: of_irq_to_resource failed...
");
            of_node_put(np);
            return -ENODEV;
        }
        printk(KERN_INFO "gpio: virq=%d
", irq);
        // check the hw irq is correct
tdata = irq_get_irq_data(irq);
        hw_irq = WARN_ON(!data)?0:data->hwirq;
        printk(KERN_INFO "gpio: hw_irq=%d
", hw_irq);
       

        if(register_chrdev(MAJOR_NUM,"gpio",&timer_intr_fops))
        {   
ttprintk(KERN_ERR "gpio: cannot register /dev/gpio
");
ttreturn -ENODEV;
t}
        // map the physical address of the timer into the virtual address space
        virt_addr = of_iomap(np, 0);
        printk(KERN_INFO "timer at 0x%08X mapped to 0x%08X
", startAddr, (u32)virt_addr);
       
        // install the irq handler
       
        result = request_irq(irq, timer_intr_irq_handler, IRQF_DISABLED, "gpio", NULL);
        if (result < 0) {
            printk(KERN_ERR "unable to request IRQ%d : %d
", irq, result);
            of_node_put(np);
            return -ENODEV;
        }
    }
   
   
   
    printk(KERN_INFO "Timer with interrupt module inserted successfully
");
   
    return 0;
}

static void __exit timer_intr_exit(void)
{
    unregister_chrdev(MAJOR_NUM,"gpio");t
    printk(KERN_INFO "Goodbye - timer_intr
");   
}

module_init(timer_intr_init);
// subsys_initcall(timer_intr_init);
module_exit(timer_intr_exit);

MODULE_AUTHOR("David VandeBunte");
MODULE_LICENSE("GPL");


before loading this module cat /proc/interrupts is not showing any interrupt for 91. after loading this module the above command is showing interrupt on 91. but it is showing 0.

output after loading my module:

[ 3248.090000] timer_intr init
[ 3248.090000] gpio: reg. size=65535 Bytes
[ 3248.100000] gpio: virq=91
[ 3248.100000] gpio: hw_irq=91
[ 3248.100000] timer at 0x81200000 mapped to 0xE08A0000
[ 3248.110000] Timer with interrupt module inserted successfully

Please help me in this.

Hi anand4miitb,

Can you please post the DTS entry related to your interrupt handler?

I just wanted to repeat the recommendations from fletch and jkrachey.  The folks at Xillinux have some excellent tutorials, in particular this one may be useful to you:

http://xillybus.com/tutorials/device-tree-zynq-4

A little over half-way down on that page, they explain the following:

"The second number is related to the interrupt number. To make a long story short, click the u201CGICu201D box in XPSu2019 main windowu2019s u201CZynqu201D tab, look up the number assigned to the interrupt (91 for xillybus in Xillinux) and subtract it by 32 (91 - 32 = 59)."

Have you accounted for this interrupt offset in your DTS such that your device is registered under the appropriate interrupt?

Regards,

-Kevin