Merge branch 'linux_next' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-edac

Pull EDAC fixes from Mauro Carvalho Chehab:
 "A series of EDAC driver fixes.  It also has one core fix at the
  documentation, and a rename patch, fixing the name of the struct that
  contains the rank information."

* 'linux_next' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-edac:
  edac: rename channel_info to rank_info
  i5400_edac: Avoid calling pci_put_device() twice
  edac: i5100 ack error detection register after each read
  edac: i5100 fix erroneous define for M1Err
  edac: sb_edac: Fix a wrong value setting for the previous value
  edac: sb_edac: Fix a INTERLEAVE_MODE() misuse
  edac: sb_edac: Let the driver depend on PCI_MMCONFIG
  edac: Improve the comments to better describe the memory concepts
  edac/ppc4xx_edac: Fix compilation
  Fix sb_edac compilation with 32 bits kernels

drivers/edac/Kconfig

@@ -215,7 +215,7 @@ config EDAC_I7300
 config EDAC_SBRIDGE
 	tristate "Intel Sandy-Bridge Integrated MC"
 	depends on EDAC_MM_EDAC && PCI && X86_64 && X86_MCE_INTEL
-	depends on EXPERIMENTAL
+	depends on PCI_MMCONFIG && EXPERIMENTAL
 	help
 	  Support for error detection and correction the Intel
 	  Sandy Bridge Integrated Memory Controller.

drivers/edac/edac_mc.c

@@ -39,7 +39,7 @@ static LIST_HEAD(mc_devices);
 
 #ifdef CONFIG_EDAC_DEBUG
 
-static void edac_mc_dump_channel(struct channel_info *chan)
+static void edac_mc_dump_channel(struct rank_info *chan)
 {
 	debugf4("\tchannel = %p\n", chan);
 	debugf4("\tchannel->chan_idx = %d\n", chan->chan_idx);
@@ -156,7 +156,7 @@ struct mem_ctl_info *edac_mc_alloc(unsigned sz_pvt, unsigned nr_csrows,
 {
 	struct mem_ctl_info *mci;
 	struct csrow_info *csi, *csrow;
-	struct channel_info *chi, *chp, *chan;
+	struct rank_info *chi, *chp, *chan;
 	void *pvt;
 	unsigned size;
 	int row, chn;
@@ -181,7 +181,7 @@ struct mem_ctl_info *edac_mc_alloc(unsigned sz_pvt, unsigned nr_csrows,
 	 * rather than an imaginary chunk of memory located at address 0.
 	 */
 	csi = (struct csrow_info *)(((char *)mci) + ((unsigned long)csi));
-	chi = (struct channel_info *)(((char *)mci) + ((unsigned long)chi));
+	chi = (struct rank_info *)(((char *)mci) + ((unsigned long)chi));
 	pvt = sz_pvt ? (((char *)mci) + ((unsigned long)pvt)) : NULL;
 
 	/* setup index and various internal pointers */

drivers/edac/i5100_edac.c

@@ -49,7 +49,7 @@
 #define		I5100_FERR_NF_MEM_M6ERR_MASK	(1 << 6)
 #define		I5100_FERR_NF_MEM_M5ERR_MASK	(1 << 5)
 #define		I5100_FERR_NF_MEM_M4ERR_MASK	(1 << 4)
-#define		I5100_FERR_NF_MEM_M1ERR_MASK	1
+#define		I5100_FERR_NF_MEM_M1ERR_MASK	(1 << 1)
 #define		I5100_FERR_NF_MEM_ANY_MASK	\
 			(I5100_FERR_NF_MEM_M16ERR_MASK | \
 			I5100_FERR_NF_MEM_M15ERR_MASK | \
@@ -535,23 +535,20 @@ static void i5100_read_log(struct mem_ctl_info *mci, int chan,
 static void i5100_check_error(struct mem_ctl_info *mci)
 {
 	struct i5100_priv *priv = mci->pvt_info;
-	u32 dw;
-
+	u32 dw, dw2;
 
 	pci_read_config_dword(priv->mc, I5100_FERR_NF_MEM, &dw);
 	if (i5100_ferr_nf_mem_any(dw)) {
-		u32 dw2;
 
 		pci_read_config_dword(priv->mc, I5100_NERR_NF_MEM, &dw2);
-		if (dw2)
-			pci_write_config_dword(priv->mc, I5100_NERR_NF_MEM,
-					       dw2);
-		pci_write_config_dword(priv->mc, I5100_FERR_NF_MEM, dw);
 
 		i5100_read_log(mci, i5100_ferr_nf_mem_chan_indx(dw),
 			       i5100_ferr_nf_mem_any(dw),
 			       i5100_nerr_nf_mem_any(dw2));
+
+		pci_write_config_dword(priv->mc, I5100_NERR_NF_MEM, dw2);
 	}
+	pci_write_config_dword(priv->mc, I5100_FERR_NF_MEM, dw);
 }
 
 /* The i5100 chipset will scrub the entire memory once, then

drivers/edac/i5400_edac.c

@@ -735,7 +735,7 @@ static int i5400_get_devices(struct mem_ctl_info *mci, int dev_idx)
 
 	/* Attempt to 'get' the MCH register we want */
 	pdev = NULL;
-	while (!pvt->branchmap_werrors || !pvt->fsb_error_regs) {
+	while (1) {
 		pdev = pci_get_device(PCI_VENDOR_ID_INTEL,
 				      PCI_DEVICE_ID_INTEL_5400_ERR, pdev);
 		if (!pdev) {
@@ -743,23 +743,42 @@ static int i5400_get_devices(struct mem_ctl_info *mci, int dev_idx)
 			i5400_printk(KERN_ERR,
 				"'system address,Process Bus' "
 				"device not found:"
-				"vendor 0x%x device 0x%x ERR funcs "
+				"vendor 0x%x device 0x%x ERR func 1 "
 				"(broken BIOS?)\n",
 				PCI_VENDOR_ID_INTEL,
 				PCI_DEVICE_ID_INTEL_5400_ERR);
-			goto error;
+			return -ENODEV;
 		}
 
-		/* Store device 16 funcs 1 and 2 */
-		switch (PCI_FUNC(pdev->devfn)) {
-		case 1:
-			pvt->branchmap_werrors = pdev;
-			break;
-		case 2:
-			pvt->fsb_error_regs = pdev;
+		/* Store device 16 func 1 */
+		if (PCI_FUNC(pdev->devfn) == 1)
 			break;
+	}
+	pvt->branchmap_werrors = pdev;
+
+	pdev = NULL;
+	while (1) {
+		pdev = pci_get_device(PCI_VENDOR_ID_INTEL,
+				      PCI_DEVICE_ID_INTEL_5400_ERR, pdev);
+		if (!pdev) {
+			/* End of list, leave */
+			i5400_printk(KERN_ERR,
+				"'system address,Process Bus' "
+				"device not found:"
+				"vendor 0x%x device 0x%x ERR func 2 "
+				"(broken BIOS?)\n",
+				PCI_VENDOR_ID_INTEL,
+				PCI_DEVICE_ID_INTEL_5400_ERR);
+
+			pci_dev_put(pvt->branchmap_werrors);
+			return -ENODEV;
 		}
+
+		/* Store device 16 func 2 */
+		if (PCI_FUNC(pdev->devfn) == 2)
+			break;
 	}
+	pvt->fsb_error_regs = pdev;
 
 	debugf1("System Address, processor bus- PCI Bus ID: %s  %x:%x\n",
 		pci_name(pvt->system_address),
@@ -778,7 +797,10 @@ static int i5400_get_devices(struct mem_ctl_info *mci, int dev_idx)
 			"MC: 'BRANCH 0' device not found:"
 			"vendor 0x%x device 0x%x Func 0 (broken BIOS?)\n",
 			PCI_VENDOR_ID_INTEL, PCI_DEVICE_ID_INTEL_5400_FBD0);
-		goto error;
+
+		pci_dev_put(pvt->fsb_error_regs);
+		pci_dev_put(pvt->branchmap_werrors);
+		return -ENODEV;
 	}
 
 	/* If this device claims to have more than 2 channels then
@@ -796,14 +818,14 @@ static int i5400_get_devices(struct mem_ctl_info *mci, int dev_idx)
 			"(broken BIOS?)\n",
 			PCI_VENDOR_ID_INTEL,
 			PCI_DEVICE_ID_INTEL_5400_FBD1);
-		goto error;
+
+		pci_dev_put(pvt->branch_0);
+		pci_dev_put(pvt->fsb_error_regs);
+		pci_dev_put(pvt->branchmap_werrors);
+		return -ENODEV;
 	}
 
 	return 0;
-
-error:
-	i5400_put_devices(mci);
-	return -ENODEV;
 }
 
 /*

drivers/edac/ppc4xx_edac.c

@@ -184,7 +184,7 @@ struct ppc4xx_ecc_status {
 
 /* Function Prototypes */
 
-static int ppc4xx_edac_probe(struct platform_device *device)
+static int ppc4xx_edac_probe(struct platform_device *device);
 static int ppc4xx_edac_remove(struct platform_device *device);
 
 /* Global Variables */
@@ -1068,7 +1068,7 @@ ppc4xx_edac_mc_init(struct mem_ctl_info *mci,
 
 	mci->mod_name		= PPC4XX_EDAC_MODULE_NAME;
 	mci->mod_ver		= PPC4XX_EDAC_MODULE_REVISION;
-	mci->ctl_name		= match->compatible,
+	mci->ctl_name		= ppc4xx_edac_match->compatible,
 	mci->dev_name		= np->full_name;
 
 	/* Initialize callbacks */

drivers/edac/sb_edac.c

@@ -20,6 +20,7 @@
 #include <linux/mmzone.h>
 #include <linux/smp.h>
 #include <linux/bitmap.h>
+#include <linux/math64.h>
 #include <asm/processor.h>
 #include <asm/mce.h>
 
@@ -670,6 +671,7 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 	u32 reg;
 	u64 limit, prv = 0;
 	u64 tmp_mb;
+	u32 mb, kb;
 	u32 rir_way;
 
 	/*
@@ -682,8 +684,9 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 	pvt->tolm = GET_TOLM(reg);
 	tmp_mb = (1 + pvt->tolm) >> 20;
 
-	debugf0("TOLM: %Lu.%03Lu GB (0x%016Lx)\n",
-		tmp_mb / 1000, tmp_mb % 1000, (u64)pvt->tolm);
+	mb = div_u64_rem(tmp_mb, 1000, &kb);
+	debugf0("TOLM: %u.%03u GB (0x%016Lx)\n",
+		mb, kb, (u64)pvt->tolm);
 
 	/* Address range is already 45:25 */
 	pci_read_config_dword(pvt->pci_sad1, TOHM,
@@ -691,8 +694,9 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 	pvt->tohm = GET_TOHM(reg);
 	tmp_mb = (1 + pvt->tohm) >> 20;
 
-	debugf0("TOHM: %Lu.%03Lu GB (0x%016Lx)",
-		tmp_mb / 1000, tmp_mb % 1000, (u64)pvt->tohm);
+	mb = div_u64_rem(tmp_mb, 1000, &kb);
+	debugf0("TOHM: %u.%03u GB (0x%016Lx)",
+		mb, kb, (u64)pvt->tohm);
 
 	/*
 	 * Step 2) Get SAD range and SAD Interleave list
@@ -714,10 +718,11 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 			break;
 
 		tmp_mb = (limit + 1) >> 20;
-		debugf0("SAD#%d %s up to %Lu.%03Lu GB (0x%016Lx) %s reg=0x%08x\n",
+		mb = div_u64_rem(tmp_mb, 1000, &kb);
+		debugf0("SAD#%d %s up to %u.%03u GB (0x%016Lx) %s reg=0x%08x\n",
 			n_sads,
 			get_dram_attr(reg),
-			tmp_mb / 1000, tmp_mb % 1000,
+			mb, kb,
 			((u64)tmp_mb) << 20L,
 			INTERLEAVE_MODE(reg) ? "Interleave: 8:6" : "Interleave: [8:6]XOR[18:16]",
 			reg);
@@ -747,8 +752,9 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 			break;
 		tmp_mb = (limit + 1) >> 20;
 
-		debugf0("TAD#%d: up to %Lu.%03Lu GB (0x%016Lx), socket interleave %d, memory interleave %d, TGT: %d, %d, %d, %d, reg=0x%08x\n",
-			n_tads, tmp_mb / 1000, tmp_mb % 1000,
+		mb = div_u64_rem(tmp_mb, 1000, &kb);
+		debugf0("TAD#%d: up to %u.%03u GB (0x%016Lx), socket interleave %d, memory interleave %d, TGT: %d, %d, %d, %d, reg=0x%08x\n",
+			n_tads, mb, kb,
 			((u64)tmp_mb) << 20L,
 			(u32)TAD_SOCK(reg),
 			(u32)TAD_CH(reg),
@@ -757,7 +763,7 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 			(u32)TAD_TGT2(reg),
 			(u32)TAD_TGT3(reg),
 			reg);
-		prv = tmp_mb;
+		prv = limit;
 	}
 
 	/*
@@ -771,9 +777,10 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 					      tad_ch_nilv_offset[j],
 					      &reg);
 			tmp_mb = TAD_OFFSET(reg) >> 20;
-			debugf0("TAD CH#%d, offset #%d: %Lu.%03Lu GB (0x%016Lx), reg=0x%08x\n",
+			mb = div_u64_rem(tmp_mb, 1000, &kb);
+			debugf0("TAD CH#%d, offset #%d: %u.%03u GB (0x%016Lx), reg=0x%08x\n",
 				i, j,
-				tmp_mb / 1000, tmp_mb % 1000,
+				mb, kb,
 				((u64)tmp_mb) << 20L,
 				reg);
 		}
@@ -795,9 +802,10 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 
 			tmp_mb = RIR_LIMIT(reg) >> 20;
 			rir_way = 1 << RIR_WAY(reg);
-			debugf0("CH#%d RIR#%d, limit: %Lu.%03Lu GB (0x%016Lx), way: %d, reg=0x%08x\n",
+			mb = div_u64_rem(tmp_mb, 1000, &kb);
+			debugf0("CH#%d RIR#%d, limit: %u.%03u GB (0x%016Lx), way: %d, reg=0x%08x\n",
 				i, j,
-				tmp_mb / 1000, tmp_mb % 1000,
+				mb, kb,
 				((u64)tmp_mb) << 20L,
 				rir_way,
 				reg);
@@ -808,9 +816,10 @@ static void get_memory_layout(const struct mem_ctl_info *mci)
 						      &reg);
 				tmp_mb = RIR_OFFSET(reg) << 6;
 
-				debugf0("CH#%d RIR#%d INTL#%d, offset %Lu.%03Lu GB (0x%016Lx), tgt: %d, reg=0x%08x\n",
+				mb = div_u64_rem(tmp_mb, 1000, &kb);
+				debugf0("CH#%d RIR#%d INTL#%d, offset %u.%03u GB (0x%016Lx), tgt: %d, reg=0x%08x\n",
 					i, j, k,
-					tmp_mb / 1000, tmp_mb % 1000,
+					mb, kb,
 					((u64)tmp_mb) << 20L,
 					(u32)RIR_RNK_TGT(reg),
 					reg);
@@ -848,6 +857,7 @@ static int get_memory_error_data(struct mem_ctl_info *mci,
 	u8			ch_way,sck_way;
 	u32			tad_offset;
 	u32			rir_way;
+	u32			mb, kb;
 	u64			ch_addr, offset, limit, prv = 0;
 
 
@@ -858,7 +868,7 @@ static int get_memory_error_data(struct mem_ctl_info *mci,
 	 * range (e. g. VGA addresses). It is unlikely, however, that the
 	 * memory controller would generate an error on that range.
 	 */
-	if ((addr > (u64) pvt->tolm) && (addr < (1L << 32))) {
+	if ((addr > (u64) pvt->tolm) && (addr < (1LL << 32))) {
 		sprintf(msg, "Error at TOLM area, on addr 0x%08Lx", addr);
 		edac_mc_handle_ce_no_info(mci, msg);
 		return -EINVAL;
@@ -913,7 +923,7 @@ static int get_memory_error_data(struct mem_ctl_info *mci,
 		addr,
 		limit,
 		sad_way + 7,
-		INTERLEAVE_MODE(reg) ? "" : "XOR[18:16]");
+		interleave_mode ? "" : "XOR[18:16]");
 	if (interleave_mode)
 		idx = ((addr >> 6) ^ (addr >> 16)) & 7;
 	else
@@ -1053,7 +1063,7 @@ static int get_memory_error_data(struct mem_ctl_info *mci,
 	ch_addr = addr & 0x7f;
 	/* Remove socket wayness and remove 6 bits */
 	addr >>= 6;
-	addr /= sck_xch;
+	addr = div_u64(addr, sck_xch);
 #if 0
 	/* Divide by channel way */
 	addr = addr / ch_way;
@@ -1073,10 +1083,10 @@ static int get_memory_error_data(struct mem_ctl_info *mci,
 			continue;
 
 		limit = RIR_LIMIT(reg);
-
-		debugf0("RIR#%d, limit: %Lu.%03Lu GB (0x%016Lx), way: %d\n",
+		mb = div_u64_rem(limit >> 20, 1000, &kb);
+		debugf0("RIR#%d, limit: %u.%03u GB (0x%016Lx), way: %d\n",
 			n_rir,
-			(limit >> 20) / 1000, (limit >> 20) % 1000,
+			mb, kb,
 			limit,
 			1 << RIR_WAY(reg));
 		if  (ch_addr <= limit)

include/linux/edac.h

@@ -70,25 +70,64 @@ enum dev_type {
 #define DEV_FLAG_X32		BIT(DEV_X32)
 #define DEV_FLAG_X64		BIT(DEV_X64)
 
-/* memory types */
+/**
+ * enum mem_type - memory types. For a more detailed reference, please see
+ *			http://en.wikipedia.org/wiki/DRAM
+ *
+ * @MEM_EMPTY		Empty csrow
+ * @MEM_RESERVED:	Reserved csrow type
+ * @MEM_UNKNOWN:	Unknown csrow type
+ * @MEM_FPM:		FPM - Fast Page Mode, used on systems up to 1995.
+ * @MEM_EDO:		EDO - Extended data out, used on systems up to 1998.
+ * @MEM_BEDO:		BEDO - Burst Extended data out, an EDO variant.
+ * @MEM_SDR:		SDR - Single data rate SDRAM
+ *			http://en.wikipedia.org/wiki/Synchronous_dynamic_random-access_memory
+ *			They use 3 pins for chip select: Pins 0 and 2 are
+ *			for rank 0; pins 1 and 3 are for rank 1, if the memory
+ *			is dual-rank.
+ * @MEM_RDR:		Registered SDR SDRAM
+ * @MEM_DDR:		Double data rate SDRAM
+ *			http://en.wikipedia.org/wiki/DDR_SDRAM
+ * @MEM_RDDR:		Registered Double data rate SDRAM
+ *			This is a variant of the DDR memories.
+ *			A registered memory has a buffer inside it, hiding
+ *			part of the memory details to the memory controller.
+ * @MEM_RMBS:		Rambus DRAM, used on a few Pentium III/IV controllers.
+ * @MEM_DDR2:		DDR2 RAM, as described at JEDEC JESD79-2F.
+ *			Those memories are labed as "PC2-" instead of "PC" to
+ *			differenciate from DDR.
+ * @MEM_FB_DDR2:	Fully-Buffered DDR2, as described at JEDEC Std No. 205
+ *			and JESD206.
+ *			Those memories are accessed per DIMM slot, and not by
+ *			a chip select signal.
+ * @MEM_RDDR2:		Registered DDR2 RAM
+ *			This is a variant of the DDR2 memories.
+ * @MEM_XDR:		Rambus XDR
+ *			It is an evolution of the original RAMBUS memories,
+ *			created to compete with DDR2. Weren't used on any
+ *			x86 arch, but cell_edac PPC memory controller uses it.
+ * @MEM_DDR3:		DDR3 RAM
+ * @MEM_RDDR3:		Registered DDR3 RAM
+ *			This is a variant of the DDR3 memories.
+ */
 enum mem_type {
-	MEM_EMPTY = 0,		/* Empty csrow */
-	MEM_RESERVED,		/* Reserved csrow type */
-	MEM_UNKNOWN,		/* Unknown csrow type */
-	MEM_FPM,		/* Fast page mode */
-	MEM_EDO,		/* Extended data out */
-	MEM_BEDO,		/* Burst Extended data out */
-	MEM_SDR,		/* Single data rate SDRAM */
-	MEM_RDR,		/* Registered single data rate SDRAM */
-	MEM_DDR,		/* Double data rate SDRAM */
-	MEM_RDDR,		/* Registered Double data rate SDRAM */
-	MEM_RMBS,		/* Rambus DRAM */
-	MEM_DDR2,		/* DDR2 RAM */
-	MEM_FB_DDR2,		/* fully buffered DDR2 */
-	MEM_RDDR2,		/* Registered DDR2 RAM */
-	MEM_XDR,		/* Rambus XDR */
-	MEM_DDR3,		/* DDR3 RAM */
-	MEM_RDDR3,		/* Registered DDR3 RAM */
+	MEM_EMPTY = 0,
+	MEM_RESERVED,
+	MEM_UNKNOWN,
+	MEM_FPM,
+	MEM_EDO,
+	MEM_BEDO,
+	MEM_SDR,
+	MEM_RDR,
+	MEM_DDR,
+	MEM_RDDR,
+	MEM_RMBS,
+	MEM_DDR2,
+	MEM_FB_DDR2,
+	MEM_RDDR2,
+	MEM_XDR,
+	MEM_DDR3,
+	MEM_RDDR3,
 };
 
 #define MEM_FLAG_EMPTY		BIT(MEM_EMPTY)
@@ -166,8 +205,9 @@ enum scrub_type {
 #define OP_OFFLINE		0x300
 
 /*
- * There are several things to be aware of that aren't at all obvious:
+ * Concepts used at the EDAC subsystem
  *
+ * There are several things to be aware of that aren't at all obvious:
  *
  * SOCKETS, SOCKET SETS, BANKS, ROWS, CHIP-SELECT ROWS, CHANNELS, etc..
  *
@@ -176,36 +216,61 @@ enum scrub_type {
  * creating a common ground for discussion, terms and their definitions
  * will be established.
  *
- * Memory devices:	The individual chip on a memory stick.  These devices
- *			commonly output 4 and 8 bits each.  Grouping several
- *			of these in parallel provides 64 bits which is common
- *			for a memory stick.
+ * Memory devices:	The individual DRAM chips on a memory stick.  These
+ *			devices commonly output 4 and 8 bits each (x4, x8).
+ *			Grouping several of these in parallel provides the
+ *			number of bits that the memory controller expects:
+ *			typically 72 bits, in order to provide 64 bits +
+ *			8 bits of ECC data.
  *
  * Memory Stick:	A printed circuit board that aggregates multiple
- *			memory devices in parallel.  This is the atomic
- *			memory component that is purchaseable by Joe consumer
- *			and loaded into a memory socket.
+ *			memory devices in parallel.  In general, this is the
+ *			Field Replaceable Unit (FRU) which gets replaced, in
+ *			the case of excessive errors. Most often it is also
+ *			called DIMM (Dual Inline Memory Module).
+ *
+ * Memory Socket:	A physical connector on the motherboard that accepts
+ *			a single memory stick. Also called as "slot" on several
+ *			datasheets.
  *
- * Socket:		A physical connector on the motherboard that accepts
- *			a single memory stick.
+ * Channel:		A memory controller channel, responsible to communicate
+ *			with a group of DIMMs. Each channel has its own
+ *			independent control (command) and data bus, and can
+ *			be used independently or grouped with other channels.
  *
- * Channel:		Set of memory devices on a memory stick that must be
- *			grouped in parallel with one or more additional
- *			channels from other memory sticks.  This parallel
- *			grouping of the output from multiple channels are
- *			necessary for the smallest granularity of memory access.
- *			Some memory controllers are capable of single channel -
- *			which means that memory sticks can be loaded
- *			individually.  Other memory controllers are only
- *			capable of dual channel - which means that memory
- *			sticks must be loaded as pairs (see "socket set").
+ * Branch:		It is typically the highest hierarchy on a
+ *			Fully-Buffered DIMM memory controller.
+ *			Typically, it contains two channels.
+ *			Two channels at the same branch can be used in single
+ *			mode or in lockstep mode.
+ *			When lockstep is enabled, the cacheline is doubled,
+ *			but it generally brings some performance penalty.
+ *			Also, it is generally not possible to point to just one
+ *			memory stick when an error occurs, as the error
+ *			correction code is calculated using two DIMMs instead
+ *			of one. Due to that, it is capable of correcting more
+ *			errors than on single mode.
  *
- * Chip-select row:	All of the memory devices that are selected together.
- *			for a single, minimum grain of memory access.
- *			This selects all of the parallel memory devices across
- *			all of the parallel channels.  Common chip-select rows
- *			for single channel are 64 bits, for dual channel 128
- *			bits.
+ * Single-channel:	The data accessed by the memory controller is contained
+ *			into one dimm only. E. g. if the data is 64 bits-wide,
+ *			the data flows to the CPU using one 64 bits parallel
+ *			access.
+ *			Typically used with SDR, DDR, DDR2 and DDR3 memories.
+ *			FB-DIMM and RAMBUS use a different concept for channel,
+ *			so this concept doesn't apply there.
+ *
+ * Double-channel:	The data size accessed by the memory controller is
+ *			interlaced into two dimms, accessed at the same time.
+ *			E. g. if the DIMM is 64 bits-wide (72 bits with ECC),
+ *			the data flows to the CPU using a 128 bits parallel
+ *			access.
+ *
+ * Chip-select row:	This is the name of the DRAM signal used to select the
+ *			DRAM ranks to be accessed. Common chip-select rows for
+ *			single channel are 64 bits, for dual channel 128 bits.
+ *			It may not be visible by the memory controller, as some
+ *			DIMM types have a memory buffer that can hide direct
+ *			access to it from the Memory Controller.
  *
  * Single-Ranked stick:	A Single-ranked stick has 1 chip-select row of memory.
  *			Motherboards commonly drive two chip-select pins to
@@ -218,8 +283,8 @@ enum scrub_type {
  *
  * Double-sided stick:	DEPRECATED TERM, see Double-Ranked stick.
  *			A double-sided stick has two chip-select rows which
- *			access different sets of memory devices.  The two
- *			rows cannot be accessed concurrently.  "Double-sided"
+ *			access different sets of memory devices. The two
+ *			rows cannot be accessed concurrently. "Double-sided"
  *			is irrespective of the memory devices being mounted
  *			on both sides of the memory stick.
  *
@@ -247,10 +312,22 @@ enum scrub_type {
  * PS - I enjoyed writing all that about as much as you enjoyed reading it.
  */
 
-struct channel_info {
-	int chan_idx;		/* channel index */
-	u32 ce_count;		/* Correctable Errors for this CHANNEL */
-	char label[EDAC_MC_LABEL_LEN + 1];	/* DIMM label on motherboard */
+/**
+ * struct rank_info - contains the information for one DIMM rank
+ *
+ * @chan_idx:	channel number where the rank is (typically, 0 or 1)
+ * @ce_count:	number of correctable errors for this rank
+ * @label:	DIMM label. Different ranks for the same DIMM should be
+ *		filled, on userspace, with the same label.
+ *		FIXME: The core currently won't enforce it.
+ * @csrow:	A pointer to the chip select row structure (the parent
+ *		structure). The location of the rank is given by
+ *		the (csrow->csrow_idx, chan_idx) vector.
+ */
+struct rank_info {
+	int chan_idx;
+	u32 ce_count;
+	char label[EDAC_MC_LABEL_LEN + 1];
 	struct csrow_info *csrow;	/* the parent */
 };
 
@@ -274,7 +351,7 @@ struct csrow_info {
 
 	/* channel information for this csrow */
 	u32 nr_channels;
-	struct channel_info *channels;
+	struct rank_info *channels;
 };
 
 struct mcidev_sysfs_group {