[coreboot-gerrit] New patch to review for coreboot: nb/intel/x4x: Fix underclocking of 800MHz DDR2 RAM

[Damien Zammit (damien@zamaudio.com)]

Damien Zammit (damien at zamaudio.com) just uploaded a new patch set to gerrit, which you can find at https://review.coreboot.org/15257

-gerrit

commit d70a8743ac3ce15eaec1c243b6e442848801c8c6
Author: Damien Zammit <damien at zamaudio.com>
Date:   Sat Jun 18 23:57:43 2016 +1000

    nb/intel/x4x: Fix underclocking of 800MHz DDR2 RAM
    
    Previously, any 800MHz dimms were being slowed to 667MHz
    for no reason other than there was a bug in the maximum
    frequency detection code for the MCH.
    
    This change also removes some unused DDR3 detection code.
    
    Change-Id: Id6c6c88c4a40631f6caf52f536a939a43cb3faf1
    Signed-off-by: Damien Zammit <damien at zamaudio.com>
---
 src/northbridge/intel/x4x/raminit.c | 50 +++----------------------------------
 1 file changed, 4 insertions(+), 46 deletions(-)

diff --git a/src/northbridge/intel/x4x/raminit.c b/src/northbridge/intel/x4x/raminit.c
index 4f5575c..7ab4697 100644
--- a/src/northbridge/intel/x4x/raminit.c
+++ b/src/northbridge/intel/x4x/raminit.c
@@ -297,7 +297,6 @@ static void sdram_detect_ram_speed(struct sysinfo *s)
 	u8 cas;
 	u8 lowcas;
 	u8 highcas;
-	u8 maxfreq;
 	u8 freq = 0;
 
 	// Find max FSB speed
@@ -317,19 +316,11 @@ static void sdram_detect_ram_speed(struct sysinfo *s)
 		break;
 	}
 
-	// Find RAM speed
-	maxfreq = (u8) ((pci_read_config16(PCI_DEV(0,0,0), 0xea) >> 4) & 0x3f);
+	// Max RAM speed
 	if (s->spd_type == DDR2) {
 
-		// Limit frequency for MCH
-		maxfreq &= 0x7;
+		// Choose max memory frequency for MCH : 800MHz
 		freq = MEM_CLOCK_800MHz;
-		if (maxfreq) {
-			freq = maxfreq;
-		}
-		if (freq > MEM_CLOCK_800MHz) {
-			freq = MEM_CLOCK_800MHz;
-		}
 
 		// Detect a common CAS latency
 		commoncas = 0xff;
@@ -408,41 +399,8 @@ static void sdram_detect_ram_speed(struct sysinfo *s)
 		}
 		s->selected_timings.mem_clk = freq;
 		s->selected_timings.CAS = cas;
-
-	} else { // DDR3
-		// Limit frequency for MCH
-		maxfreq >>= 3;
-		freq = MEM_CLOCK_1333MHz;
-		if (maxfreq) {
-			freq = maxfreq + 2;
-		}
-		if (freq > MEM_CLOCK_1333MHz) {
-			freq = MEM_CLOCK_1333MHz;
-		}
-
-		// Limit DDR speed to FSB speed
-		switch (s->max_fsb) {
-		case FSB_CLOCK_800MHz:
-			if (freq > MEM_CLOCK_800MHz) {
-				freq = MEM_CLOCK_800MHz;
-			}
-			break;
-		case FSB_CLOCK_1066MHz:
-			if (freq > MEM_CLOCK_1066MHz) {
-				freq = MEM_CLOCK_1066MHz;
-			}
-			break;
-		case FSB_CLOCK_1333MHz:
-			if (freq > MEM_CLOCK_1333MHz) {
-				freq = MEM_CLOCK_1333MHz;
-			}
-			break;
-		default:
-			die("Invalid FSB\n");
-			break;
-		}
-
-		// TODO: CAS detection for DDR3
+	} else {
+		die("Wrong DDR type\n");
 	}
 }