Hi,
according to the PPC440EPx Embedded Processor User Manual (rev 1.14)
DDR0_14[REDUC] bit has the following meaning:
REDUC - Enable the half data path feature of the controller
0 = Standard operation using full 64/72-bit memory bus
1 = Memory data path width is 32/40 bits
However, "1" is decoded as 64 bit (8 byte), "0" - as 32 bit (4 byte) bus
by the kernel code. My understanding is this is not correct - patch
attached.
--- linux.orig/arch/powerpc/boot/4xx.c 2009-03-09 17:55:01.000000000 +0200
+++ linux/arch/powerpc/boot/4xx.c 2009-03-09 17:58:07.000000000 +0200
@@ -193,9 +193,9 @@
val = SDRAM0_READ(DDR0_14);
if (DDR_GET_VAL(val, DDR_REDUC, DDR_REDUC_SHIFT))
- dpath = 8; /* 64 bits */
- else
dpath = 4; /* 32 bits */
+ else
+ dpath = 8; /* 64 bits */
/* get address pins (rows) */
val = SDRAM0_READ(DDR0_42);
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