lightnvm: introduce mlc lower page table mappings

NAND MLC memories have both lower and upper pages. When programming,
both of these must be written, before data can be read. However,
these lower and upper pages might not placed at even and odd flash
pages, but can be skipped. Therefore each flash memory has its lower
pages defined, which can then be used when programming and to know when
padding are necessary.

This patch implements the lower page definition in the specification,
and exposes it through a simple lookup table at dev->lptbl.

Signed-off-by: Matias Bjørling <m@bjorling.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/lightnvm/core.c

@@ -362,6 +362,51 @@ int nvm_submit_ppa(struct nvm_dev *dev, struct ppa_addr *ppa, int nr_ppas,
 }
 EXPORT_SYMBOL(nvm_submit_ppa);
 
+static int nvm_init_slc_tbl(struct nvm_dev *dev, struct nvm_id_group *grp)
+{
+	int i;
+
+	dev->lps_per_blk = dev->pgs_per_blk;
+	dev->lptbl = kcalloc(dev->lps_per_blk, sizeof(int), GFP_KERNEL);
+	if (!dev->lptbl)
+		return -ENOMEM;
+
+	/* Just a linear array */
+	for (i = 0; i < dev->lps_per_blk; i++)
+		dev->lptbl[i] = i;
+
+	return 0;
+}
+
+static int nvm_init_mlc_tbl(struct nvm_dev *dev, struct nvm_id_group *grp)
+{
+	int i, p;
+	struct nvm_id_lp_mlc *mlc = &grp->lptbl.mlc;
+
+	if (!mlc->num_pairs)
+		return 0;
+
+	dev->lps_per_blk = mlc->num_pairs;
+	dev->lptbl = kcalloc(dev->lps_per_blk, sizeof(int), GFP_KERNEL);
+	if (!dev->lptbl)
+		return -ENOMEM;
+
+	/* The lower page table encoding consists of a list of bytes, where each
+	 * has a lower and an upper half. The first half byte maintains the
+	 * increment value and every value after is an offset added to the
+	 * previous incrementation value */
+	dev->lptbl[0] = mlc->pairs[0] & 0xF;
+	for (i = 1; i < dev->lps_per_blk; i++) {
+		p = mlc->pairs[i >> 1];
+		if (i & 0x1) /* upper */
+			dev->lptbl[i] = dev->lptbl[i - 1] + ((p & 0xF0) >> 4);
+		else /* lower */
+			dev->lptbl[i] = dev->lptbl[i - 1] + (p & 0xF);
+	}
+
+	return 0;
+}
+
 static int nvm_core_init(struct nvm_dev *dev)
 {
 	struct nvm_id *id = &dev->identity;
@@ -387,11 +432,23 @@ static int nvm_core_init(struct nvm_dev *dev)
 		return -EINVAL;
 	}
 
-	if (grp->fmtype != 0 && grp->fmtype != 1) {
+	switch (grp->fmtype) {
+	case NVM_ID_FMTYPE_SLC:
+		if (nvm_init_slc_tbl(dev, grp))
+			return -ENOMEM;
+		break;
+	case NVM_ID_FMTYPE_MLC:
+		if (nvm_init_mlc_tbl(dev, grp))
+			return -ENOMEM;
+		break;
+	default:
 		pr_err("nvm: flash type not supported\n");
 		return -EINVAL;
 	}
 
+	if (!dev->lps_per_blk)
+		pr_info("nvm: lower page programming table missing\n");
+
 	if (grp->mpos & 0x020202)
 		dev->plane_mode = NVM_PLANE_DOUBLE;
 	if (grp->mpos & 0x040404)
@@ -420,6 +477,8 @@ static void nvm_free(struct nvm_dev *dev)
 
 	if (dev->mt)
 		dev->mt->unregister_mgr(dev);
+
+	kfree(dev->lptbl);
 }
 
 static int nvm_init(struct nvm_dev *dev)