Fix SPD cas latency assert bug

aamarin · crgeddes · commit 877a032b90cd · 2019-03-01T10:18:10.000-06:00
Change-Id: Ic38888f6db211e16385f5223ff267fd7044c6758 Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/72250 Tested-by: FSP CI Jenkins <fsp-CI-jenkins+hostboot@us.ibm.com> Tested-by: Jenkins Server <pfd-jenkins+hostboot@us.ibm.com> Tested-by: HWSV CI <hwsv-ci+hostboot@us.ibm.com> Tested-by: Hostboot CI <hostboot-ci+hostboot@us.ibm.com> Reviewed-by: Louis Stermole <stermole@us.ibm.com> Reviewed-by: STEPHEN GLANCY <sglancy@us.ibm.com> Dev-Ready: ANDRE A. MARIN <aamarin@us.ibm.com> Reviewed-by: Jennifer A. Stofer <stofer@us.ibm.com> Reviewed-on: http://rchgit01.rchland.ibm.com/gerrit1/72316 Tested-by: Jenkins OP Build CI <op-jenkins+hostboot@us.ibm.com> Tested-by: Jenkins OP HW <op-hw-jenkins+hostboot@us.ibm.com> Reviewed-by: Christian R. Geddes <crgeddes@us.ibm.com>
diff --git a/src/import/generic/memory/lib/spd/common/ddr4/spd_decoder_ddr4.H b/src/import/generic/memory/lib/spd/common/ddr4/spd_decoder_ddr4.H
@@ -1189,11 +1189,19 @@ class decoder<DDR4, BASE_CNFG, R> : public base_cnfg_decoder
                 right_aligned_insert(l_buffer, l_fourth_raw_byte, l_third_raw_byte, l_sec_raw_byte, l_first_raw_byte);
 
                 // According to the JEDEC spec:
-                // Byte 22 (Bits 7~0) and Byte 23 are reserved and thus not supported
-                // Check for a valid value
-                constexpr size_t MAX_VALID_VAL = 0x3FFFF;
+                // Byte 22 (Bits 7~0) and Byte 23 are reserved in the base revision SPD general section
+                // Only bit 6 (right-aligned) for Byte 23 is reserved for subsequent SPD revisions
+                // Check for a valid value, and that reserved bit is not set
+                // We return Byte 23 arbitrarily as the failed byte, but any byte (20 - 23) would work
+                constexpr size_t MAX_VALID_VAL = (R == rev::V1_0) ? 0x0003FFFF : 0xBFFFFFFF;
+
+                constexpr uint64_t DATA_START_OFFSET  = 32;
+                constexpr uint64_t RESERVED_BIT = DATA_START_OFFSET + 1;
+                // Bit 6 of byte 23 must be 0 (reserved for future use)
+                const bool RESERVED_BIT_VALUE = l_buffer.getBit<RESERVED_BIT>();
+
                 FAPI_TRY( mss::check::invalid_value(iv_target,
-                                                    l_buffer <= MAX_VALID_VAL,
+                                                    l_buffer <= MAX_VALID_VAL && !RESERVED_BIT_VALUE,
                                                     23,
                                                     l_buffer,
                                                     mss::BAD_SPD_DATA,
