sbc8548: Make enabling SPD RAM configuration work

Previously, SPD configuration of RAM was non functional on
this board.  Now that the root cause is known (an i2c address
conflict), there is a simple end-user workaround - remove the
old slower local bus 128MB module and then SPD detection on the
main DDR2 memory module works fine.

We make the enablement of the LBC SDRAM support conditional on
being not SPD enabled.  We can revisit this dependency as the
hardware workaround becomes available.

Turning off LBC SDRAM support revealed a couple implict dependencies
in the tlb/law code that always expected an LBC SDRAM address.

This has been tested with the default 256MB module, a 512MB
a 1GB and a 2GB, of varying speeds, and the SPD autoconfiguration
worked fine in all cases.

The default configuration remains to go with the hard coded
DDR config, so the default build will continue to work on boards
where people don't bother to read the docs.  But the advantage
of going to the SPD config is that even the small default module
gets configured for CL3 instead of CL4.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 12 insertions, 1 deletions

diff --git a/include/configs/sbc8548.h b/include/configs/sbc8548.h
index 1df2225a77..44c75269ce 100644
--- a/include/configs/sbc8548.h
+++ b/include/configs/sbc8548.h
@@ -119,9 +119,15 @@
 /* DDR Setup */
 #define CONFIG_FSL_DDR2
 #undef CONFIG_FSL_DDR_INTERACTIVE
+#undef CONFIG_DDR_ECC			/* only for ECC DDR module */
+/*
+ * A hardware errata caused the LBC SDRAM SPD and the DDR2 SPD
+ * to collide, meaning you couldn't reliably read either. So
+ * physically remove the LBC PC100 SDRAM module from the board
+ * before enabling the two SPD options below.
+ */
 #undef CONFIG_SPD_EEPROM		/* Use SPD EEPROM for DDR setup */
 #undef CONFIG_DDR_SPD
-#undef CONFIG_DDR_ECC			/* only for ECC DDR module */
 
 #define CONFIG_ECC_INIT_VIA_DDRCONTROLLER	/* DDR controller or DMA? */
 #define CONFIG_MEM_INIT_VALUE	0xDeadBeef
@@ -283,9 +289,14 @@
 
 /*
  * SDRAM on the Local Bus (CS3 and CS4)
+ * Note that most boards have a hardware errata where both the
+ * LBC SDRAM and the DDR2 SDRAM decode at 0x51, making it impossible
+ * to use CONFIG_DDR_SPD unless you physically remove the LBC DIMM.
  */
+#ifndef CONFIG_DDR_SPD
 #define CONFIG_SYS_LBC_SDRAM_BASE	0xf0000000	/* Localbus SDRAM */
 #define CONFIG_SYS_LBC_SDRAM_SIZE	128		/* LBC SDRAM is 128MB */
+#endif
 
 /*
  * Base Register 3 and Option Register 3 configure the 1st 1/2 SDRAM.