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Subject[PATCH v3 04/31] drivers/edac: rename channel_info to csrow_channel_info
Date
Newer memory architectures use the term "channel" with a different
meaning.

On a traditional architecture, the memory controller directly
access the memory ranks, via chip select rows.

The memory controller and the memory configuration can be single-channel
or double-channel. Single-channel means 64 bits access, while dual-channel
means 128 parallel access, provided by two memory sticks that are accessed
at the same time. The addresses between channel A and channel B are
interleaved. The memories on each channel should be identical for it
to work.

When two channels are provided, the DIMM memories are generally called
DIMM 1A/DIMM 1B (where 1A means DIMM 1 at channel A, and so on).

On some modern memory architectures like FB-DIMM, there's a microcontroller
chip, called Advanced Memory Buffer (AMB) that serves as the interface
between the memory controller and the memory chips. So, the memory
controller sees independent memory channels, and doesn't actually select
the memory by a "chip select". Instead, it passes the DIMM slot it wants
to access to the AMB.

It is up to the AMB to talk with the csrows of the DRAM chips.

The bus that exchanges information between the memory controller and
the CPU is also called "channel", but it is not associated with
the channel interleaving, as each channel is independent. The entire
csrow concept is not even visible to the memory controller, as using
csrows is a task for the AMB.

Newer memory controllers like the one found on Intel Sandy Bridge
processors, even when working with normal DDR3 DIMM's, don't use the
channel A/channel B interleaving schema to provide 128 bits. Instead,
they have more channels (3 or 4 channels), and several interleaving
schemas are supported, and a csrow concept is not directly visible by
the memory controller.

The drivers that support such such newer memory architecture models
currently need to fake information and to abuse on EDAC structures,
as the subsystem was conceived with the idea that the csrow would always
be visible by the CPU.

To make things a little worse, those drivers don't currently fake
csrows/channels on a consistent way, as the concepts there don't
apply to the memory controllers they're talking with.

In order to fix it, let's rename "channel" to "cschannel", in order to
be clearer that this channel info will only be used when the csrows
concept applies.

Latter patchsets will provide a better way to represent the memory
hierarchy on a way that will work with other memory architectures.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
---
drivers/edac/edac_mc.c | 6 +++---
include/linux/edac.h | 6 +++---
2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 5038239..8776f30 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -43,7 +43,7 @@ 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 csrow_channel_info *chan)
{
debugf4("\tchannel = %p\n", chan);
debugf4("\tchannel->chan_idx = %d\n", chan->chan_idx);
@@ -160,7 +160,7 @@ 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 csrow_channel_info *chi, *chp, *chan;
void *pvt;
unsigned size;
int row, chn;
@@ -185,7 +185,7 @@ 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 csrow_channel_info *)(((char *)mci) + ((unsigned long)chi));
pvt = sz_pvt ? (((char *)mci) + ((unsigned long)pvt)) : NULL;

/* setup index and various internal pointers */
diff --git a/include/linux/edac.h b/include/linux/edac.h
index 3ba99d7..6e3ab94 100644
--- a/include/linux/edac.h
+++ b/include/linux/edac.h
@@ -191,7 +191,7 @@ enum scrub_type {
* Socket: A physical connector on the motherboard that accepts
* a single memory stick.
*
- * Channel: Set of memory devices on a memory stick that must be
+ * Csrow-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
@@ -249,7 +249,7 @@ enum scrub_type {
* PS - I enjoyed writing all that about as much as you enjoyed reading it.
*/

-struct channel_info {
+struct csrow_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 */
@@ -276,7 +276,7 @@ struct csrow_info {

/* channel information for this csrow */
u32 nr_channels;
- struct channel_info *channels;
+ struct csrow_channel_info *channels;
};

struct mcidev_sysfs_group {
--
1.7.8


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