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Power down discrete graphic chip on apple gmux
#include <stdio.h>
#include <sys/io.h>
#define GMUX_PORT_SWITCH_DISPLAY 0x10
#define GMUX_PORT_SWITCH_DDC 0x28
#define GMUX_PORT_SWITCH_EXTERNAL 0x40
#define GMUX_PORT_DISCRETE_POWER 0x50
#define GMUX_PORT_VALUE 0xc2
#define GMUX_PORT_READ 0xd0
#define GMUX_PORT_WRITE 0xd4
#define GMUX_IOSTART 0x700
typedef unsigned char u8;
enum discrete_state {STATE_ON, STATE_OFF};
enum gpu_id {IGD, DIS};
static void index_write8(int port, u8 val)
{
outb(val, GMUX_IOSTART + GMUX_PORT_VALUE);
outb((port & 0xff), GMUX_IOSTART + GMUX_PORT_WRITE);
}
static u8 index_read8(int port)
{
u8 val;
outb((port & 0xff), GMUX_IOSTART + GMUX_PORT_READ);
val = inb(GMUX_IOSTART + GMUX_PORT_VALUE);
return val;
}
static void set_discrete_state(enum discrete_state state)
{
if (state == STATE_ON) { // switch on dGPU
index_write8(GMUX_PORT_DISCRETE_POWER, 1);
index_write8(GMUX_PORT_DISCRETE_POWER, 3);
} else { // switch off dGPU
index_write8(GMUX_PORT_DISCRETE_POWER, 1);
index_write8(GMUX_PORT_DISCRETE_POWER, 0);
}
}
static u8 get_discrete_state()
{
return index_read8(GMUX_PORT_DISCRETE_POWER);
}
static void switchto(enum gpu_id id)
{
if (id == IGD) { // switch to iGPU
index_write8(GMUX_PORT_SWITCH_DDC, 1);
index_write8(GMUX_PORT_SWITCH_DISPLAY, 2);
index_write8(GMUX_PORT_SWITCH_EXTERNAL, 2);
} else { // switch to dGPU
index_write8(GMUX_PORT_SWITCH_DDC, 2);
index_write8(GMUX_PORT_SWITCH_DISPLAY, 3);
index_write8(GMUX_PORT_SWITCH_EXTERNAL, 3);
}
}
int main(int argc, char **argv)
{
if (iopl(3) < 0) {
perror("No IO permissions");
return 1;
}
//switchto(IGD);
set_discrete_state(STATE_OFF);
//printf("Discrete state: 0x%X\n", get_discrete_state());
return 0;
}
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