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Changed RAM speed calculation to fix RAM modules getting rejected only 

due to integer rounding errors. Previously, the formula was:
	speed = 2 * (10000/spd_value)
For spd_value=60 this means speed = 2 * 166 = 332, which is less than
333 and coreboot died saying RAM was incompatible. The new formula is:
	speed = 20000 / spd_value
For spd_value=60, speed=333, which is fine.

Signed-off-by: Jens Rottmann <JRottmann@LiPPERTEmbedded.de>
Acked-by: Marc Jones <marc.jones@amd.com>


git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3689 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
This commit is contained in:
Jens Rottmann 2008-10-22 22:26:09 +00:00 committed by Marc Jones
parent 5e5bef5fbd
commit f6fa12d89e
1 changed files with 5 additions and 6 deletions
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11
src/northbridge/amd/lx/raminit.c
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@ -194,7 +194,7 @@ static void checkDDRMax(void)
} }
/* Turn SPD ns time into MHZ. Check what the asm does to this math. */ /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
speed = 2 * ((10000 / (((spd_byte0 >> 4) * 10) + (spd_byte0 & 0x0F)))); speed = 20000 / (((spd_byte0 >> 4) * 10) + (spd_byte0 & 0x0F));
/* current speed > max speed? */ /* current speed > max speed? */
if (GeodeLinkSpeed() > speed) { if (GeodeLinkSpeed() > speed) {
@ -274,15 +274,14 @@ static void setCAS(void)
spd_byte = spd_read_byte(DIMM0, SPD_SDRAM_CYCLE_TIME_2ND); spd_byte = spd_read_byte(DIMM0, SPD_SDRAM_CYCLE_TIME_2ND);
if (spd_byte != 0) { if (spd_byte != 0) {
/* Turn SPD ns time into MHZ. Check what the asm does to this math. */ /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + dimm_speed = 20000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F));
(spd_byte & 0x0F)));
if (dimm_speed >= glspeed) { if (dimm_speed >= glspeed) {
casmap_shift = 1; /* -.5 is a shift of 1 */ casmap_shift = 1; /* -.5 is a shift of 1 */
/* IF -1 timing is supported, check -1 timing > GeodeLink */ /* IF -1 timing is supported, check -1 timing > GeodeLink */
spd_byte = spd_read_byte(DIMM0, SPD_SDRAM_CYCLE_TIME_3RD); spd_byte = spd_read_byte(DIMM0, SPD_SDRAM_CYCLE_TIME_3RD);
if (spd_byte != 0) { if (spd_byte != 0) {
/* Turn SPD ns time into MHZ. Check what the asm does to this math. */ /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F))); dimm_speed = 20000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F));
if (dimm_speed >= glspeed) { if (dimm_speed >= glspeed) {
casmap_shift = 2; /* -1 is a shift of 2 */ casmap_shift = 2; /* -1 is a shift of 2 */
} }
@ -306,14 +305,14 @@ static void setCAS(void)
spd_byte = spd_read_byte(DIMM1, SPD_SDRAM_CYCLE_TIME_2ND); spd_byte = spd_read_byte(DIMM1, SPD_SDRAM_CYCLE_TIME_2ND);
if (spd_byte != 0) { if (spd_byte != 0) {
/* Turn SPD ns time into MHZ. Check what the asm does to this math. */ /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F))); dimm_speed = 20000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F));
if (dimm_speed >= glspeed) { if (dimm_speed >= glspeed) {
casmap_shift = 1; /* -.5 is a shift of 1 */ casmap_shift = 1; /* -.5 is a shift of 1 */
/* IF -1 timing is supported, check -1 timing > GeodeLink */ /* IF -1 timing is supported, check -1 timing > GeodeLink */
spd_byte = spd_read_byte(DIMM1, SPD_SDRAM_CYCLE_TIME_3RD); spd_byte = spd_read_byte(DIMM1, SPD_SDRAM_CYCLE_TIME_3RD);
if (spd_byte != 0) { if (spd_byte != 0) {
/* Turn SPD ns time into MHZ. Check what the asm does to this math. */ /* Turn SPD ns time into MHZ. Check what the asm does to this math. */
dimm_speed = 2 * (10000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F))); dimm_speed = 20000 / (((spd_byte >> 4) * 10) + (spd_byte & 0x0F));
if (dimm_speed >= glspeed) { if (dimm_speed >= glspeed) {
casmap_shift = 2; /* -1 is a shift of 2 */ casmap_shift = 2; /* -1 is a shift of 2 */
} }