mtd: mxc_nand: limit the size of used oob

For 4k pages the i.MX NFC hardware uses no more than 218 bytes for 8bit ECC
data. Larger oobsize confuses the logic of copy_spare(). Limit the size of used
oob size to avoid that.

Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
index 5bbc1c5..ceeb61c 100644 (file)
--- a/drivers/mtd/nand/mxc_nand.c
+++ b/drivers/mtd/nand/mxc_nand.c
@@ -189,6 +189,7 @@ struct mxc_nand_host {
        int                     clk_act;
        int                     irq;
        int                     eccsize;
+       int                     used_oobsize;
        int                     active_cs;
 
        struct completion       op_completion;
@@ -827,7 +828,7 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom)
        u16 sparebuf_size = host->devtype_data->spare_len;
 
        /* size of oob chunk for all but possibly the last one */
-       oob_chunk_size = (mtd->oobsize / num_chunks) & ~1;
+       oob_chunk_size = (host->used_oobsize / num_chunks) & ~1;
 
        if (bfrom) {
                for (i = 0; i < num_chunks - 1; i++)
@@ -838,7 +839,7 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom)
                /* the last chunk */
                memcpy32_fromio(d + i * oob_chunk_size,
                                s + i * sparebuf_size,
-                               mtd->oobsize - i * oob_chunk_size);
+                               host->used_oobsize - i * oob_chunk_size);
        } else {
                for (i = 0; i < num_chunks - 1; i++)
                        memcpy32_toio(&s[i * sparebuf_size],
@@ -848,7 +849,7 @@ static void copy_spare(struct mtd_info *mtd, bool bfrom)
                /* the last chunk */
                memcpy32_toio(&s[oob_chunk_size * sparebuf_size],
                              &d[i * oob_chunk_size],
-                             mtd->oobsize - i * oob_chunk_size);
+                             host->used_oobsize - i * oob_chunk_size);
        }
 }
 
@@ -1606,6 +1607,15 @@ static int mxcnd_probe(struct platform_device *pdev)
        else if (mtd->writesize == 4096)
                this->ecc.layout = host->devtype_data->ecclayout_4k;
 
+       /*
+        * Experimentation shows that i.MX NFC can only handle up to 218 oob
+        * bytes. Limit used_oobsize to 218 so as to not confuse copy_spare()
+        * into copying invalid data to/from the spare IO buffer, as this
+        * might cause ECC data corruption when doing sub-page write to a
+        * partially written page.
+        */
+       host->used_oobsize = min(mtd->oobsize, 218U);
+
        if (this->ecc.mode == NAND_ECC_HW) {
                if (is_imx21_nfc(host) || is_imx27_nfc(host))
                        this->ecc.strength = 1;