Improve DIMM detection for AMCC Yucca 440SPe board

Improved the memory DIMM detection for the Yucca 440SPe board for
the case where a memory DIMM is falsely detected as present.

This issue is seen on some AMCC Yucca 440SPe validation boards if
only one 512MB memory DIMM is installed, i.e. DIMM slot 0 is
populated and DIMM slot 1 is empty.  In this case, U-Boot does
not correctly detect that there is only one DIMM memory module
installed and will falsely detect two DIMM memory modules are
present and therefore U-Boot will not calculate the correct amount
of total memory and u-boot will not booting up.

Patch by Adam Graham, 24 Aug 2006

diff --git a/CHANGELOG b/CHANGELOG
index e326782..a044b8e 100644 (file)
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -2,6 +2,18 @@
 Changes since U-Boot 1.1.4:
 ======================================================================
 
+* Improve DIMM detection for AMCC Yucca 440SPe board
+  Improved the memory DIMM detection for the Yucca 440SPe board for
+  the case where a memory DIMM is falsely detected as present.
+  This issue is seen on some AMCC Yucca 440SPe validation boards if
+  only one 512MB memory DIMM is installed, i.e. DIMM slot 0 is
+  populated and DIMM slot 1 is empty.  In this case, U-Boot does
+  not correctly detect that there is only one DIMM memory module
+  installed and will falsely detect two DIMM memory modules are
+  present and therefore U-Boot will not calculate the correct amount
+  of total memory and u-boot will not booting up.
+  Patch by Adam Graham, 24 Aug 2006
+
 * Code cleanup
 
 * Update for MCC200 / PRS200 boards:

diff --git a/board/amcc/yucca/yucca.c b/board/amcc/yucca/yucca.c
index af12839..65f7575 100644 (file)
--- a/board/amcc/yucca/yucca.c
+++ b/board/amcc/yucca/yucca.c
@@ -562,10 +562,11 @@ int checkboard (void)
 
 static long int yucca_probe_for_dimms(void)
 {
-       long int        dimm_installed[MAXDIMMS];
-       long int        dimm_num, probe_result;
-       long int        dimms_found = 0;
-       uchar           dimm_addr = IIC0_DIMM0_ADDR;
+       int     dimm_installed[MAXDIMMS];
+       int     dimm_num, result;
+       int     dimms_found = 0;
+       uchar   dimm_addr = IIC0_DIMM0_ADDR;
+       uchar   dimm_spd_data[MAX_SPD_BYTES];
 
        for (dimm_num = 0; dimm_num < MAXDIMMS; dimm_num++) {
                /* check if there is a chip at the dimm address */
@@ -577,12 +578,28 @@ static long int yucca_probe_for_dimms(void)
                                dimm_addr = IIC0_DIMM1_ADDR;
                                break;
                }
-               probe_result = i2c_probe(dimm_addr);
 
-               if (probe_result == 0) {
+               result = i2c_probe(dimm_addr);
+
+               memset(dimm_spd_data, 0, MAX_SPD_BYTES * sizeof(char));
+               if (result == 0) {
+                       /* read first byte of SPD data, if there is any data */ 
+                       result = i2c_read(dimm_addr, 0, 1, dimm_spd_data, 1);
+
+                       if (result == 0) {
+                               result = dimm_spd_data[0];
+                               result = result > MAX_SPD_BYTES ? 
+                                               MAX_SPD_BYTES : result;
+                               result = i2c_read(dimm_addr, 0, 1,
+                                                       dimm_spd_data, result);
+                       }
+               }
+
+               if ((result == 0) &&
+                   (dimm_spd_data[64] == MICRON_SPD_JEDEC_ID)) {       
                        dimm_installed[dimm_num] = TRUE;
                        dimms_found++;
-                       debug("DIMM slot %d: DDR2 SDRAM detected\n",dimm_num);
+                       debug("DIMM slot %d: DDR2 SDRAM detected\n", dimm_num);
                } else {
                        dimm_installed[dimm_num] = FALSE;
                        debug("DIMM slot %d: Not populated or cannot sucessfully probe the DIMM\n", dimm_num);

diff --git a/board/amcc/yucca/yucca.h b/board/amcc/yucca/yucca.h
index 66f7584..4d13021 100644 (file)
--- a/board/amcc/yucca/yucca.h
+++ b/board/amcc/yucca/yucca.h
@@ -60,6 +60,9 @@ extern "C" {
 
 #define NUM_TLB_ENTRIES          64
 
+/* MICRON SPD JEDEC ID Code (first byte) - SPD data byte [64] */
+#define MICRON_SPD_JEDEC_ID 0x2c
+
 /*----------------------------------------------------------------------------+
 | TLB specific defines.
 +----------------------------------------------------------------------------*/