[PATCH RESEND v3 13/17] EDAC/mc: Add MC unique index allocation procedure

Serge Semin
2022-09-29T23:33:08Z

In case of the unique index allocation it's not that optimal to always
rely on the low-level device drivers (platform drivers), because they get
to start to implement either the same design pattern (for instance global
static MC counter) or may end-up with having non-unique index eventually
at runtime. Needless to say that having a generic unique index
allocation/tracking procedure will make code more readable and safer.

The suggested implementation is based on the kernel IDA infrastructure
exposed by the lib/idr.c driver with API described in linux/idr.h header
file. It's used to create an ID resource descriptor "mc_idr", which then
is utilized either to track the custom MC idx specified by EDAC LLDDs or
to allocate the next-free MC idx.

A new special MC index is introduced here. It's defined by the
EDAC_AUTO_MC_NUM macro with a value specifically chosen as the least
probable value used for the real MC index. In case if the EDAC_AUTO_MC_NUM
index is specified by the EDAC LLDD, the MC index will be either retrieved
from the MC device OF-node alias index ("mc[:number:]") or automatically
generated as the next-free MC index found by the ID allocation procedure.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>

---

Note the approach implemented here has been partly ported from the SPI
core driver using IDA to track/allocate SPI bus numbers.
Link: https://elixir.bootlin.com/linux/latest/source/drivers/spi/spi.c#L2957
---
drivers/edac/edac_mc.c | 89 +++++++++++++++++++++++++++++++++++++++---
drivers/edac/edac_mc.h | 4 ++
2 files changed, 87 insertions(+), 6 deletions(-)

diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
index 24814839d885..634c41ea7804 100644
--- a/drivers/edac/edac_mc.c
+++ b/drivers/edac/edac_mc.c
@@ -29,6 +29,9 @@
#include <linux/edac.h>
#include <linux/bitops.h>
#include <linux/uaccess.h>
+#include <linux/idr.h>
+#include <linux/of.h>
+
#include <asm/page.h>
#include "edac_mc.h"
#include "edac_module.h"
@@ -46,6 +49,7 @@ EXPORT_SYMBOL_GPL(edac_op_state);
/* lock to memory controller's control array */
static DEFINE_MUTEX(mem_ctls_mutex);
static LIST_HEAD(mc_devices);
+static DEFINE_IDR(mc_idr);

/*
* Used to lock EDAC MC to just one module, avoiding two drivers e. g.
@@ -493,7 +497,64 @@ void edac_mc_reset_delay_period(unsigned long value)
mutex_unlock(&mem_ctls_mutex);
}

+/**
+ * edac_mc_alloc_id() - Allocate unique Memory Controller identifier
+ *
+ * @mci: pointer to the mci structure to allocate ID for
+ *
+ * Use edac_mc_free_id() to coherently free the MC identifier.
+ *
+ * .. note::
+ * locking model: must be called with the mem_ctls_mutex lock held
+ *
+ * Returns:
+ * 0 on Success, or an error code on failure
+ */
+static int edac_mc_alloc_id(struct mem_ctl_info *mci)
+{
+ struct device_node *np = dev_of_node(mci->pdev);
+ int ret, min, max;
+
+ if (mci->mc_idx == EDAC_AUTO_MC_NUM) {
+ ret = of_alias_get_id(np, "mc");
+ if (ret >= 0) {
+ min = ret;
+ max = ret + 1;
+ } else {
+ min = of_alias_get_highest_id("mc");
+ if (min >= 0)
+ min++;
+ else
+ min = 0;
+
+ max = 0;
+ }
+ } else {
+ min = mci->mc_idx;
+ max = mci->mc_idx + 1;
+ }
+
+ ret = idr_alloc(&mc_idr, mci, min, max, GFP_KERNEL);
+ if (ret < 0)
+ return ret == -ENOSPC ? -EBUSY : ret;
+
+ mci->mc_idx = ret;
+
+ return 0;
+}

+/**
+ * edac_mc_free_id() - Free Memory Controller identifier
+ *
+ * @mci: pointer to the mci structure to free ID from
+ *
+ * .. note::
+ * locking model: must be called with the mem_ctls_mutex lock held
+ */
+static void edac_mc_free_id(struct mem_ctl_info *mci)
+{
+ idr_remove(&mc_idr, mci->mc_idx);
+}

/**
* edac_mc_init_labels() - Initialize DIMM labels
@@ -612,7 +673,8 @@ EXPORT_SYMBOL_GPL(edac_get_owner);
int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
const struct attribute_group **groups)
{
- int ret = -EINVAL;
+ int ret;
+
edac_dbg(0, "\n");

#ifdef CONFIG_EDAC_DEBUG
@@ -649,20 +711,30 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
goto fail0;
}

+ ret = edac_mc_alloc_id(mci);
+ if (ret) {
+ edac_printk(KERN_ERR, EDAC_MC, "failed to allocate MC idx %u\n",
+ mci->mc_idx);
+ goto fail0;
+ }
+
edac_mc_init_labels(mci);

- if (add_mc_to_global_list(mci))
- goto fail0;
+ if (add_mc_to_global_list(mci)) {
+ ret = -EINVAL;
+ goto fail1;
+ }

/* set load time so that error rate can be tracked */
mci->start_time = jiffies;

mci->bus = edac_get_sysfs_subsys();

- if (edac_create_sysfs_mci_device(mci, groups)) {
+ ret = edac_create_sysfs_mci_device(mci, groups);
+ if (ret) {
edac_mc_printk(mci, KERN_WARNING,
"failed to create sysfs device\n");
- goto fail1;
+ goto fail2;
}

if (mci->edac_check) {
@@ -686,9 +758,12 @@ int edac_mc_add_mc_with_groups(struct mem_ctl_info *mci,
mutex_unlock(&mem_ctls_mutex);
return 0;

-fail1:
+fail2:
del_mc_from_global_list(mci);

+fail1:
+ edac_mc_free_id(mci);
+
fail0:
mutex_unlock(&mem_ctls_mutex);
return ret;
@@ -716,6 +791,8 @@ struct mem_ctl_info *edac_mc_del_mc(struct device *dev)
if (del_mc_from_global_list(mci))
edac_mc_owner = NULL;

+ edac_mc_free_id(mci);
+
mutex_unlock(&mem_ctls_mutex);

if (mci->edac_check)
diff --git a/drivers/edac/edac_mc.h b/drivers/edac/edac_mc.h
index 881b00eadf7a..4b6676235b1b 100644
--- a/drivers/edac/edac_mc.h
+++ b/drivers/edac/edac_mc.h
@@ -23,6 +23,7 @@
#define _EDAC_MC_H_

#include <linux/kernel.h>
+#include <linux/limits.h>
#include <linux/types.h>
#include <linux/module.h>
#include <linux/spinlock.h>
@@ -37,6 +38,9 @@
#include <linux/workqueue.h>
#include <linux/edac.h>

+/* Generate MC identifier automatically */
+#define EDAC_AUTO_MC_NUM UINT_MAX
+
#if PAGE_SHIFT < 20
#define PAGES_TO_MiB(pages) ((pages) >> (20 - PAGE_SHIFT))
#define MiB_TO_PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
--
2.37.3