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Old 04-27-2017, 02:27 AM   #1
annjer
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Registered: Apr 2017
Posts: 1

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Coding serial ISR for UART 16550 under Linux kernel 3.18


Hello,
I have a problem with my ISR made on the basis of http://http://www.linuxquestions.org...-linux-763595/Coding an Interrupt Service Routine for the serial port in Linux !! post. Here is my code:
Code:
#include <linux/kernel.h>
#include <linux/module.h>	
#include <linux/interrupt.h> 
#include <linux/version.h>
#include <linux/fs.h>
#include <asm/io.h>
#include <asm/signal.h>
#include <linux/irq.h>
#define PORT 0x3F8

void delayedOp (unsigned long currentlyUnused);
DECLARE_TASKLET (rs232Tasklet, delayedOp, 0);

static int times;
static unsigned char znak;
unsigned char status, intr_identify;
irq_handler_t isrSerialPort (int irq, void *dev_id, struct pt_regs *regs)
{
	times++;
	printk (KERN_ALERT "\nisrSerialPort called %d ", times);

	intr_identify = inb( PORT + 2 ) & 0x0F;
	if ( intr_identify == 0x01 ) return  IRQ_NONE;
	 
	if ( intr_identify == 0x04 )     // a new character has arrived 
	znak=inb( PORT );
	printk ("   irq =  %x, intr = %x ", znak,intr_identify);
	outb(znak,PORT);
	tasklet_schedule (&rs232Tasklet);
	outb(0x20,0x20);
	return (irq_handler_t) IRQ_HANDLED;
}

int init_module ()
{
	int	status;
	int result = request_irq (4, (irq_handler_t) isrSerialPort, IRQF_DISABLED, "softbrainISR", NULL);

	outb(0x0b,PORT+4);	//ster_modem - DTR,RTS,OUT2
	outb( 0x07, PORT + 2 );	// turn off FIFO-mode 
	inb(PORT+6);	//stan_modem
	inb(PORT+5);	//status_port
	inb(PORT);		//dane
	outb(0x8b,PORT+3);		//LCR=1, param_trans = 0x0b - parity even (b3-b5), 1 bit stopu(b2), 8 bitów danych (b0,b1)
							//03 - dla parity none
	outb(0x0c,PORT);		//9600 bodów
	outb(0x0b,PORT+3);		//LCR=0
	outb(01,PORT+1);		//przerwanie od odbiornika aktyw_przerw=1
	status=inb(PORT+5);		
	if(status&01)inb(PORT);
	inb(PORT);
	printk (KERN_INFO "\ncinit_module called\n");
	return result;
}

void delayedOp (unsigned long currentlyUnused)
{
	printk ("\nznak =  %x ", znak);
}

void cleanup_module ()
{
	free_irq (4, NULL);
	printk (KERN_INFO "\ncleanup_module called\n");
}
The problem is that the first interrupt doesn't come - the first character I send comes after I send the next character and so on... In effect I never get the last one - It waits for interrupt until next character.

Where is the problem?
Please help me
Anna
 
Old 04-28-2017, 06:48 PM   #2
AwesomeMachine
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Registered: Jan 2005
Location: USA and Italy
Distribution: Debian testing/sid; OpenSuSE; Fedora; Mint
Posts: 5,513

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Hi Anna,

Welcome to LQ!

OK, for this you must learn the debugger. It will allow you to step through the code while monitoring what is going on. If I had to figure this out, that is what I'd need to do.
 
  


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