mtd: nandsim: Introduce debugfs infrastructure

It's more user friendly to report debug information and statistics
through debugfs, than to use printing facilites.

This patch introduces a very minimal debugfs infrastructure
and moves eraseblock wear report to an entry located at:

/sys/kernel/debug/nandsim/wear_report

This means we can remove rptwear option and just let
the user get the wear report when we needs to.

Signed-off-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>

1 files changed, 130 insertions, 56 deletions

diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index a932c485eb0..2ab827428f1 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -42,6 +42,8 @@
 #include <linux/sched.h>
 #include <linux/fs.h>
 #include <linux/pagemap.h>
+#include <linux/seq_file.h>
+#include <linux/debugfs.h>
 
 /* Default simulator parameters values */
 #if !defined(CONFIG_NANDSIM_FIRST_ID_BYTE)  || \
@@ -105,7 +107,6 @@ static char *weakblocks = NULL;
 static char *weakpages = NULL;
 static unsigned int bitflips = 0;
 static char *gravepages = NULL;
-static unsigned int rptwear = 0;
 static unsigned int overridesize = 0;
 static char *cache_file = NULL;
 static unsigned int bbt;
@@ -130,7 +131,6 @@ module_param(weakblocks,     charp, 0400);
 module_param(weakpages,      charp, 0400);
 module_param(bitflips,       uint, 0400);
 module_param(gravepages,     charp, 0400);
-module_param(rptwear,        uint, 0400);
 module_param(overridesize,   uint, 0400);
 module_param(cache_file,     charp, 0400);
 module_param(bbt,            uint, 0400);
@@ -162,7 +162,6 @@ MODULE_PARM_DESC(bitflips,       "Maximum number of random bit flips per page (z
 MODULE_PARM_DESC(gravepages,     "Pages that lose data [: maximum reads (defaults to 3)]"
                                  " separated by commas e.g. 1401:2 means page 1401"
                                  " can be read only twice before failing");
-MODULE_PARM_DESC(rptwear,        "Number of erases between reporting wear, if not zero");
 MODULE_PARM_DESC(overridesize,   "Specifies the NAND Flash size overriding the ID bytes. "
                                  "The size is specified in erase blocks and as the exponent of a power of two"
                                  " e.g. 5 means a size of 32 erase blocks");
@@ -286,6 +285,11 @@ MODULE_PARM_DESC(bch,		 "Enable BCH ecc and set how many bits should "
 /* Maximum page cache pages needed to read or write a NAND page to the cache_file */
 #define NS_MAX_HELD_PAGES 16
 
+struct nandsim_debug_info {
+        struct dentry *dfs_root;
+        struct dentry *dfs_wear_report;
+};
+
 /*
  * A union to represent flash memory contents and flash buffer.
  */
@@ -365,6 +369,8 @@ struct nandsim {
         void *file_buf;
         struct page *held_pages[NS_MAX_HELD_PAGES];
         int held_cnt;
+
+        struct nandsim_debug_info dbg;
 };
 
 /*
@@ -442,11 +448,123 @@ static LIST_HEAD(grave_pages);
 static unsigned long *erase_block_wear = NULL;
 static unsigned int wear_eb_count = 0;
 static unsigned long total_wear = 0;
-static unsigned int rptwear_cnt = 0;
 
 /* MTD structure for NAND controller */
 static struct mtd_info *nsmtd;
 
+static int nandsim_debugfs_show(struct seq_file *m, void *private)
+{
+        unsigned long wmin = -1, wmax = 0, avg;
+        unsigned long deciles[10], decile_max[10], tot = 0;
+        unsigned int i;
+
+        /* Calc wear stats */
+        for (i = 0; i < wear_eb_count; ++i) {
+                unsigned long wear = erase_block_wear[i];
+                if (wear < wmin)
+                        wmin = wear;
+                if (wear > wmax)
+                        wmax = wear;
+                tot += wear;
+        }
+
+        for (i = 0; i < 9; ++i) {
+                deciles[i] = 0;
+                decile_max[i] = (wmax * (i + 1) + 5) / 10;
+        }
+        deciles[9] = 0;
+        decile_max[9] = wmax;
+        for (i = 0; i < wear_eb_count; ++i) {
+                int d;
+                unsigned long wear = erase_block_wear[i];
+                for (d = 0; d < 10; ++d)
+                        if (wear <= decile_max[d]) {
+                                deciles[d] += 1;
+                                break;
+                        }
+        }
+        avg = tot / wear_eb_count;
+
+        /* Output wear report */
+        seq_printf(m, "Total numbers of erases:  %lu\n", tot);
+        seq_printf(m, "Number of erase blocks:   %u\n", wear_eb_count);
+        seq_printf(m, "Average number of erases: %lu\n", avg);
+        seq_printf(m, "Maximum number of erases: %lu\n", wmax);
+        seq_printf(m, "Minimum number of erases: %lu\n", wmin);
+        for (i = 0; i < 10; ++i) {
+                unsigned long from = (i ? decile_max[i - 1] + 1 : 0);
+                if (from > decile_max[i])
+                        continue;
+                seq_printf(m, "Number of ebs with erase counts from %lu to %lu : %lu\n",
+                        from,
+                        decile_max[i],
+                        deciles[i]);
+        }
+
+        return 0;
+}
+
+static int nandsim_debugfs_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, nandsim_debugfs_show, inode->i_private);
+}
+
+static const struct file_operations dfs_fops = {
+        .open           = nandsim_debugfs_open,
+        .read           = seq_read,
+        .llseek         = seq_lseek,
+        .release        = single_release,
+};
+
+/**
+ * nandsim_debugfs_create - initialize debugfs
+ * @dev: nandsim device description object
+ *
+ * This function creates all debugfs files for UBI device @ubi. Returns zero in
+ * case of success and a negative error code in case of failure.
+ */
+static int nandsim_debugfs_create(struct nandsim *dev)
+{
+        struct nandsim_debug_info *dbg = &dev->dbg;
+        struct dentry *dent;
+        int err;
+
+        if (!IS_ENABLED(CONFIG_DEBUG_FS))
+                return 0;
+
+        dent = debugfs_create_dir("nandsim", NULL);
+        if (IS_ERR_OR_NULL(dent)) {
+                int err = dent ? -ENODEV : PTR_ERR(dent);
+
+                NS_ERR("cannot create \"nandsim\" debugfs directory, err %d\n",
+                        err);
+                return err;
+        }
+        dbg->dfs_root = dent;
+
+        dent = debugfs_create_file("wear_report", S_IRUSR,
+                                   dbg->dfs_root, dev, &dfs_fops);
+        if (IS_ERR_OR_NULL(dent))
+                goto out_remove;
+        dbg->dfs_wear_report = dent;
+
+        return 0;
+
+out_remove:
+        debugfs_remove_recursive(dbg->dfs_root);
+        err = dent ? PTR_ERR(dent) : -ENODEV;
+        return err;
+}
+
+/**
+ * nandsim_debugfs_remove - destroy all debugfs files
+ */
+static void nandsim_debugfs_remove(struct nandsim *ns)
+{
+        if (IS_ENABLED(CONFIG_DEBUG_FS))
+                debugfs_remove_recursive(ns->dbg.dfs_root);
+}
+
 /*
  * Allocate array of page pointers, create slab allocation for an array
  * and initialize the array by NULL pointers.
@@ -911,8 +1029,6 @@ static int setup_wear_reporting(struct mtd_info *mtd)
 {
         size_t mem;
 
-        if (!rptwear)
-                return 0;
         wear_eb_count = div_u64(mtd->size, mtd->erasesize);
         mem = wear_eb_count * sizeof(unsigned long);
         if (mem / sizeof(unsigned long) != wear_eb_count) {
@@ -929,64 +1045,18 @@ static int setup_wear_reporting(struct mtd_info *mtd)
 
 static void update_wear(unsigned int erase_block_no)
 {
-        unsigned long wmin = -1, wmax = 0, avg;
-        unsigned long deciles[10], decile_max[10], tot = 0;
-        unsigned int i;
-
         if (!erase_block_wear)
                 return;
         total_wear += 1;
+        /*
+         * TODO: Notify this through a debugfs entry,
+         * instead of showing an error message.
+         */
         if (total_wear == 0)
                 NS_ERR("Erase counter total overflow\n");
         erase_block_wear[erase_block_no] += 1;
         if (erase_block_wear[erase_block_no] == 0)
                 NS_ERR("Erase counter overflow for erase block %u\n", erase_block_no);
-        rptwear_cnt += 1;
-        if (rptwear_cnt < rptwear)
-                return;
-        rptwear_cnt = 0;
-        /* Calc wear stats */
-        for (i = 0; i < wear_eb_count; ++i) {
-                unsigned long wear = erase_block_wear[i];
-                if (wear < wmin)
-                        wmin = wear;
-                if (wear > wmax)
-                        wmax = wear;
-                tot += wear;
-        }
-        for (i = 0; i < 9; ++i) {
-                deciles[i] = 0;
-                decile_max[i] = (wmax * (i + 1) + 5) / 10;
-        }
-        deciles[9] = 0;
-        decile_max[9] = wmax;
-        for (i = 0; i < wear_eb_count; ++i) {
-                int d;
-                unsigned long wear = erase_block_wear[i];
-                for (d = 0; d < 10; ++d)
-                        if (wear <= decile_max[d]) {
-                                deciles[d] += 1;
-                                break;
-                        }
-        }
-        avg = tot / wear_eb_count;
-        /* Output wear report */
-        NS_INFO("*** Wear Report ***\n");
-        NS_INFO("Total numbers of erases:  %lu\n", tot);
-        NS_INFO("Number of erase blocks:   %u\n", wear_eb_count);
-        NS_INFO("Average number of erases: %lu\n", avg);
-        NS_INFO("Maximum number of erases: %lu\n", wmax);
-        NS_INFO("Minimum number of erases: %lu\n", wmin);
-        for (i = 0; i < 10; ++i) {
-                unsigned long from = (i ? decile_max[i - 1] + 1 : 0);
-                if (from > decile_max[i])
-                        continue;
-                NS_INFO("Number of ebs with erase counts from %lu to %lu : %lu\n",
-                        from,
-                        decile_max[i],
-                        deciles[i]);
-        }
-        NS_INFO("*** End of Wear Report ***\n");
 }
 
 /*
@@ -2330,6 +2400,9 @@ static int __init ns_init_module(void)
         if ((retval = setup_wear_reporting(nsmtd)) != 0)
                 goto err_exit;
 
+        if ((retval = nandsim_debugfs_create(nand)) != 0)
+                goto err_exit;
+
         if ((retval = init_nandsim(nsmtd)) != 0)
                 goto err_exit;
 
@@ -2369,6 +2442,7 @@ static void __exit ns_cleanup_module(void)
         struct nandsim *ns = ((struct nand_chip *)nsmtd->priv)->priv;
         int i;
 
+        nandsim_debugfs_remove(ns);
         free_nandsim(ns);    /* Free nandsim private resources */
         nand_release(nsmtd); /* Unregister driver */
         for (i = 0;i < ARRAY_SIZE(ns->partitions); ++i)