Timothy Pearson (tpearson(a)raptorengineeringinc.com) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/12007
-gerrit
commit 19e7f908352b60b5f683bf35c1836dc7627cc633
Author: Timothy Pearson <tpearson(a)raptorengineeringinc.com>
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 <tpearson(a)raptorengineeringinc.com>
---
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;