edac: mpc85xx mask ecc syndrome correctly

With a 64-bit wide data bus only the lowest 8-bits of the ECC syndrome are
relevant. With a 32-bit wide data bus only the lowest 16-bits are
relevant on most architectures.

Without this change, the ECC syndrome displayed can be mildly confusing,
eg:

EDAC MPC85xx MC1: syndrome: 0x25252525

When in reality the ECC syndrome is 0x25.

A variety of Freescale manuals say a variety of different things about how
to decode the CAPTURE_ECC (syndrome) register. I don't have a system with
a 32-bit bus to test on, but I believe the change is correct. It'd be
good to get an ACK from someone at Freescale about this change though.

Signed-off-by: Peter Tyser <[e-mail]>
Signed-off-by: Doug Thompson <[e-mail]>
Cc: Kumar Gala <[e-mail]>
Cc: Dave Jiang <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/edac/mpc85xx_edac.c

···
 {
 	struct mpc85xx_mc_pdata *pdata = mci->pvt_info;
 	struct csrow_info *csrow;
+	u32 bus_width;
 	u32 err_detect;
 	u32 syndrome;
 	u32 err_addr;
···
 	}
 
 	syndrome = in_be32(pdata->mc_vbase + MPC85XX_MC_CAPTURE_ECC);
+
+	/* Mask off appropriate bits of syndrome based on bus width */
+	bus_width = (in_be32(pdata->mc_vbase + MPC85XX_MC_DDR_SDRAM_CFG) &
+			DSC_DBW_MASK) ? 32 : 64;
+	if (bus_width == 64)
+		syndrome &= 0xff;
+	else
+		syndrome &= 0xffff;
+
 	err_addr = in_be32(pdata->mc_vbase + MPC85XX_MC_CAPTURE_ADDRESS);
 	pfn = err_addr >> PAGE_SHIFT;
 
···
 	mpc85xx_mc_printk(mci, KERN_ERR, "Capture Data Low: %#8.8x\n",
 			  in_be32(pdata->mc_vbase +
 				  MPC85XX_MC_CAPTURE_DATA_LO));
-	mpc85xx_mc_printk(mci, KERN_ERR, "syndrome: %#8.8x\n", syndrome);
+	mpc85xx_mc_printk(mci, KERN_ERR, "syndrome: %#2.2x\n", syndrome);
 	mpc85xx_mc_printk(mci, KERN_ERR, "err addr: %#8.8x\n", err_addr);
 	mpc85xx_mc_printk(mci, KERN_ERR, "PFN: %#8.8x\n", pfn);
 

drivers/edac/mpc85xx_edac.h

···
 #define DSC_MEM_EN	0x80000000
 #define DSC_ECC_EN	0x20000000
 #define DSC_RD_EN	0x10000000
+#define DSC_DBW_MASK	0x00180000
+#define DSC_DBW_32	0x00080000
+#define DSC_DBW_64	0x00000000
 
 #define DSC_SDTYPE_MASK		0x07000000