powerpc/mpc8xxx: Add 16-bit support for DDR3

Add support for 16-bit DDR bus. Also deal with system using 64- and 32-bit
DDR devices.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/cpu/mpc8xxx/ddr/main.c

@@ -174,7 +174,19 @@ int step_assign_addresses(fsl_ddr_info_t *pinfo,
 		switch (pinfo->memctl_opts[i].data_bus_width) {
 		case 2:
 			/* 16-bit */
-			printf("can't handle 16-bit mode yet\n");
+			for (j = 0; j < CONFIG_DIMM_SLOTS_PER_CTLR; j++) {
+				unsigned int dw;
+				if (!pinfo->dimm_params[i][j].n_ranks)
+					continue;
+				dw = pinfo->dimm_params[i][j].primary_sdram_width;
+				if ((dw == 72 || dw == 64)) {
+					dbw_cap_adj[i] = 2;
+					break;
+				} else if ((dw == 40 || dw == 32)) {
+					dbw_cap_adj[i] = 1;
+					break;
+				}
+			}
 			break;
 
 		case 1:

arch/powerpc/cpu/mpc8xxx/ddr/options.c

@@ -438,7 +438,8 @@ unsigned int populate_memctl_options(int all_DIMMs_registered,
 	popts->OTF_burst_chop_en = 0;	/* on-the-fly burst chop disable */
 	popts->burst_length = DDR_BL8;	/* Fixed 8-beat burst len */
 #else
-	if (popts->data_bus_width == 1) {	/* 32-bit bus */
+	if ((popts->data_bus_width == 1) || (popts->data_bus_width == 2)) {
+		/* 32-bit or 16-bit bus */
 		popts->OTF_burst_chop_en = 0;
 		popts->burst_length = DDR_BL8;
 	} else {

arch/powerpc/include/asm/fsl_ddr_sdram.h

@@ -181,6 +181,9 @@ typedef struct memctl_options_partial_s {
 	unsigned int all_DIMMs_minimum_tRCD_ps;
 } memctl_options_partial_t;
 
+#define DDR_DATA_BUS_WIDTH_64 0
+#define DDR_DATA_BUS_WIDTH_32 1
+#define DDR_DATA_BUS_WIDTH_16 2
 /*
  * Generalized parameters for memory controller configuration,
  * might be a little specific to the FSL memory controller