src/pc80/i8259.c

/*
 * This file is part of the coreboot project.
 *
 * Copyright (C) 2009 coresystems GmbH
 *
 * 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; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#include <arch/io.h>
#include <pc80/i8259.h>
#include <console/console.h>

#define MASTER_PIC_ICW1		0x20
#define SLAVE_PIC_ICW1		0xa0
#define   ICW_SELECT		(1 << 4)
#define   OCW_SELECT		(0 << 4)
#define   ADI			(1 << 2)
#define   SNGL			(1 << 1)
#define   IC4			(1 << 0)

#define MASTER_PIC_ICW2		0x21
#define SLAVE_PIC_ICW2		0xa1
#define   INT_VECTOR_MASTER	0x20
#define   IRQ0			0x00
#define   IRQ1			0x01
#define   INT_VECTOR_SLAVE	0x28
#define   IRQ8			0x00
#define   IRQ9			0x01

#define MASTER_PIC_ICW3		0x21
#define   CASCADED_PIC		(1 << 2)

#define MASTER_PIC_ICW4		0x21
#define SLAVE_PIC_ICW4		0xa1
#define   MICROPROCESSOR_MODE	(1 << 0)

#define SLAVE_PIC_ICW3		0xa1
#define    SLAVE_ID		0x02

#define MASTER_PIC_OCW1 	0x21
#define SLAVE_PIC_OCW1		0xa1
#define    IRQ2			(1 << 2)
#define    ALL_IRQS		0xff

#define ELCR1			0x4d0
#define ELCR2			0x4d1

void setup_i8259(void)
{
	/* A write to ICW1 starts the Interrupt Controller Initialization
	 * Sequence. This implicitly causes the following to happen:
	 *   - Interrupt Mask register is cleared
	 *   - Priority 7 is assigned to IRQ7 input
	 *   - Slave mode address is set to 7
	 *   - Special mask mode is cleared
	 *
	 * We send the initialization sequence to both the master and
	 * slave i8259 controller.
	 */
	outb(ICW_SELECT|IC4, MASTER_PIC_ICW1);
	outb(ICW_SELECT|IC4, SLAVE_PIC_ICW1);

	/* Now the interrupt controller expects us to write to ICW2. */
	outb(INT_VECTOR_MASTER | IRQ0, MASTER_PIC_ICW2);
	outb(INT_VECTOR_SLAVE  | IRQ8, SLAVE_PIC_ICW2);

	/* Now the interrupt controller expects us to write to ICW3. 
	 *
	 * The normal scenario is to set up cascading on IRQ2 on the master
	 * i8259 and assign the slave ID 2 to the slave i8259.
	 */
	outb(CASCADED_PIC, MASTER_PIC_ICW3);
	outb(SLAVE_ID, SLAVE_PIC_ICW3);

	/* Now the interrupt controller expects us to write to ICW4.
	 *
	 * We switch both i8259 to microprocessor mode because they're
	 * operating as part of an x86 architecture based chipset
	 */
	outb(MICROPROCESSOR_MODE, MASTER_PIC_ICW2);
	outb(MICROPROCESSOR_MODE, SLAVE_PIC_ICW2);		

	/* Now clear the interrupts through OCW1. 
	 * First we mask off all interrupts on the slave interrupt controller
	 * then we mask off all interrupts but interrupt 2 on the master
	 * controller. This way the cascading stays alife.
	 */
	outb(ALL_IRQS, SLAVE_PIC_OCW1);
	outb(ALL_IRQS & ~IRQ2, MASTER_PIC_OCW1);
}

/**
 * @brief Configure IRQ triggering in the i8259 compatible Interrupt Controller.
 *
 * Switch a certain interrupt to be level / edge triggered.
 *
 * @param int_num legacy interrupt number (3-7, 9-15)
 * @param is_level_triggered 1 for level triggered interrupt, 0 for edge
 *        triggered interrupt
 */
void i8259_configure_irq_trigger(int int_num, int is_level_triggered)
{
	u16 int_bits = inb(ELCR1) | (((u16)inb(ELCR2)) << 8);

	printk(BIOS_SPEW, "%s: current interrupts are 0x%x\n", __func__, int_bits);
	if (is_level_triggered)
		int_bits |= (1 << int_num);
	else
		int_bits &= ~(1 << int_num);

	/* Write new values */
	printk(BIOS_SPEW, "%s: try to set interrupts 0x%x\n", __func__, int_bits);
	outb((u8)(int_bits & 0xff), ELCR1);
	outb((u8)(int_bits >> 8), ELCR2);

#ifdef PARANOID_IRQ_TRIGGERS
	/* Try reading back the new values. This seems like an error but is not ... */
	if (inb(ELCR1) != (int_bits & 0xff)) {
		printk(BIOS_ERR, "%s: lower order bits are wrong: want 0x%x, got 0x%x\n",
				__func__, (int_bits & 0xff), inb(ELCR1));
	}

	if (inb(ELCR2) != (int_bits >> 8)) {
		printk(BIOS_ERR, "%s: higher order bits are wrong: want 0x%x, got 0x%x\n",
				__func__, (int_bits>>8), inb(ELCR2));
	}
#endif
}