Patch set updated for coreboot: northbridge/amd/amdmct/mct_ddr3: Work around strange phy training issue

[Timothy Pearson]

Timothy Pearson ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/12007

-gerrit

commit 19e7f908352b60b5f683bf35c1836dc7627cc633
Author: Timothy Pearson 
Date:   Thu Jun 25 18:37:45 2015 -0500

northbridge/amd/amdmct/mct_ddr3: Work around strange phy training issue

AMD Opteron processors contain a very fragile phy phase detection circuit.
    Additionally, the algorithm given in the BKDG does not function as intended;
    this was verified both on real hardware via execution trace and on paper
    with values read back from multiple CPUs and DIMMs.

As a result, the phy training algorithm given in the BKDG has been
    replaced with a phy training algorithm developed at Raptor Engineering.
    This particular patch is the first part of that algorithm; the code
    is updated in future patches but this should exist in the historical
    record in case something breaks down in the later sections of code.

Change-Id: Ic7a19d24954f47c922126e3da7be1f7e85f7396f
    Signed-off-by: Timothy Pearson 
---
 src/northbridge/amd/amdmct/mct_ddr3/mhwlc_d.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/src/northbridge/amd/amdmct/mct_ddr3/mhwlc_d.c b/src/northbridge/amd/amdmct/mct_ddr3/mhwlc_d.c
index 496803e..dfddb60 100644
--- a/src/northbridge/amd/amdmct/mct_ddr3/mhwlc_d.c
+++ b/src/northbridge/amd/amdmct/mct_ddr3/mhwlc_d.c
@@ -203,6 +203,22 @@ uint8_t AgesaHwWlPhase2(struct MCTStatStruc *pMCTstat, struct DCTStatStruc *pDCT

pDCTData->WLCriticalGrossDelayPrevPass = cgd;

+		if (pDCTstat->Speed != pDCTstat->TargetFreq) {
+			/* FIXME
+			 * Using the Pass 1 training values causes major phy training problems on
+			 * all Family 15h processors I tested (Pass 1 values are randomly too high,
+			 * and Pass 2 cannot lock).
+			 * Figure out why this is and fix it, then remove the bypass code below...
+			 */
+			if (pass == FirstPass) {
+				for (ByteLane = 0; ByteLane < MAX_BYTE_LANES; ByteLane++) {
+					pDCTData->WLGrossDelay[index+ByteLane] = pDCTData->WLSeedGrossDelay[index+ByteLane];
+					pDCTData->WLFineDelay[index+ByteLane] = pDCTData->WLSeedFineDelay[index+ByteLane];
+				}
+				return 0;
+			}
+		}
+
    	/* Compensate for occasional noise/instability causing sporadic training failure */
    	for (ByteLane = 0; ByteLane < MAX_BYTE_LANES; ByteLane++) {
    		uint8_t faulty_value_detected = 0;