44 lines
1.2 KiB
C
44 lines
1.2 KiB
C
|
|
static void spd_enable_refresh(void)
|
|
{
|
|
/*
|
|
* Effects: Uses serial presence detect to set the
|
|
* refresh rate in the DRAMC register.
|
|
* see spd_set_dramc for the other values.
|
|
* FIXME: Check for illegal/unsupported ram configurations and abort
|
|
*/
|
|
static const unsigned char refresh_rates[] = {
|
|
0x01, /* Normal 15.625 us -> 15.6 us */
|
|
0x05, /* Reduced(.25X) 3.9 us -> 7.8 us */
|
|
0x05, /* Reduced(.5X) 7.8 us -> 7.8 us */
|
|
0x02, /* Extended(2x) 31.3 us -> 31.2 us */
|
|
0x03, /* Extended(4x) 62.5 us -> 62.4 us */
|
|
0x04, /* Extended(8x) 125 us -> 124.8 us */
|
|
};
|
|
/* Find the first dimm and assume the rest are the same */
|
|
int byte;
|
|
unsigned device;
|
|
unsigned refresh_rate;
|
|
byte = -1;
|
|
device = 0x50;
|
|
while ((byte < 0) && (device <= 0x57)) {
|
|
byte = __builtin_inl(device);
|
|
device += 1;
|
|
}
|
|
if (byte < 0) {
|
|
/* We couldn't find anything we must have no memory */
|
|
while(1);
|
|
}
|
|
byte &= 0x7f;
|
|
/* Default refresh rate be conservative */
|
|
refresh_rate = 5;
|
|
/* see if the ram refresh is a supported one */
|
|
if (byte < 6) {
|
|
refresh_rate = refresh_rates[byte];
|
|
}
|
|
byte = __builtin_inb(0x57);
|
|
byte &= 0xf8;
|
|
byte |= refresh_rate;
|
|
__builtin_outb(byte, 0x57);
|
|
}
|