mtd: nand: sunxi: implement ->read_subpage()

Being able to read subpages can greatly improve read performances if the
MTD user is only interested in a small section of a NAND page.
This is particularly true with large pages (>= 8k).

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index d8ad50f..e4d487c 100644 (file)
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -973,6 +973,39 @@ static int sunxi_nfc_hw_ecc_read_page(struct mtd_info *mtd,
        return max_bitflips;
 }
 
+static int sunxi_nfc_hw_ecc_read_subpage(struct mtd_info *mtd,
+                                        struct nand_chip *chip,
+                                        u32 data_offs, u32 readlen,
+                                        u8 *bufpoi, int page)
+{
+       struct nand_ecc_ctrl *ecc = &chip->ecc;
+       int ret, i, cur_off = 0;
+       unsigned int max_bitflips = 0;
+
+       sunxi_nfc_hw_ecc_enable(mtd);
+
+       chip->cmdfunc(mtd, NAND_CMD_READ0, 0, page);
+       for (i = data_offs / ecc->size;
+            i < DIV_ROUND_UP(data_offs + readlen, ecc->size); i++) {
+               int data_off = i * ecc->size;
+               int oob_off = i * (ecc->bytes + 4);
+               u8 *data = bufpoi + data_off;
+               u8 *oob = chip->oob_poi + oob_off;
+
+               ret = sunxi_nfc_hw_ecc_read_chunk(mtd, data, data_off,
+                                                 oob,
+                                                 oob_off + mtd->writesize,
+                                                 &cur_off, &max_bitflips,
+                                                 !i, page);
+               if (ret < 0)
+                       return ret;
+       }
+
+       sunxi_nfc_hw_ecc_disable(mtd);
+
+       return max_bitflips;
+}
+
 static int sunxi_nfc_hw_ecc_write_page(struct mtd_info *mtd,
                                       struct nand_chip *chip,
                                       const uint8_t *buf, int oob_required,
@@ -1389,6 +1422,7 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct mtd_info *mtd,
        ecc->write_page = sunxi_nfc_hw_ecc_write_page;
        ecc->read_oob_raw = nand_read_oob_std;
        ecc->write_oob_raw = nand_write_oob_std;
+       ecc->read_subpage = sunxi_nfc_hw_ecc_read_subpage;
        layout = ecc->layout;
        nsectors = mtd->writesize / ecc->size;
 
@@ -1635,6 +1669,8 @@ static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *nfc,
        if (nand->options & NAND_NEED_SCRAMBLING)
                nand->options |= NAND_NO_SUBPAGE_WRITE;
 
+       nand->options |= NAND_SUBPAGE_READ;
+
        ret = sunxi_nand_chip_init_timings(chip, np);
        if (ret) {
                dev_err(dev, "could not configure chip timings: %d\n", ret);