[PATCH v3 1/4] mtd: nand: mxc_nand: cleanup copy_spare function

Baruch Siach
2015-05-13T08:17:36Z

From: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

To give people without the reference manual at hand a chance to
understand how spare area is handled in the i.MX nand controller,
improve commenting, naming of variables and coding style.

No functional change intended.

Reviewed-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
[baruch: declare oob_chunk_size; update comments; reword commit log]
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
drivers/mtd/nand/mxc_nand.c | 46 ++++++++++++++++++++++++++++++---------------
1 file changed, 31 insertions(+), 15 deletions(-)

diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
index 372e0e38f59b..33b22b9c0b30 100644
--- a/drivers/mtd/nand/mxc_nand.c
+++ b/drivers/mtd/nand/mxc_nand.c
@@ -807,32 +807,48 @@ static void mxc_nand_select_chip_v2(struct mtd_info *mtd, int chip)
}

/*
- * Function to transfer data to/from spare area.
+ * The controller splits a page into data chunks of 512 bytes + partial oob.
+ * There are writesize / 512 such chunks, the size of the partial oob parts is
+ * oobsize / #chunks rounded down to a multiple of 2. The last oob chunk then
+ * contains additionally the byte lost by rounding (if any).
+ * This function handles the needed shuffling between host->data_buf (which
+ * holds a page in natural order, i.e. writesize bytes data + oobsize bytes
+ * spare) and the NFC buffer.
*/
static void copy_spare(struct mtd_info *mtd, bool bfrom)
{
struct nand_chip *this = mtd->priv;
struct mxc_nand_host *host = this->priv;
- u16 i, j;
- u16 n = mtd->writesize >> 9;
+ u16 i, oob_chunk_size;
+ u16 num_chunks = mtd->writesize / 512;
+
u8 *d = host->data_buf + mtd->writesize;
u8 __iomem *s = host->spare0;
- u16 t = host->devtype_data->spare_len;
+ u16 sparebuf_size = host->devtype_data->spare_len;

- j = (mtd->oobsize / n >> 1) << 1;
+ /* size of oob chunk for all but possibly the last one */
+ oob_chunk_size = (mtd->oobsize / num_chunks) & ~1;

if (bfrom) {
- for (i = 0; i < n - 1; i++)
- memcpy32_fromio(d + i * j, s + i * t, j);
-
- /* the last section */
- memcpy32_fromio(d + i * j, s + i * t, mtd->oobsize - i * j);
+ for (i = 0; i < num_chunks - 1; i++)
+ memcpy32_fromio(d + i * oob_chunk_size,
+ s + i * sparebuf_size,
+ oob_chunk_size);
+
+ /* the last chunk */
+ memcpy32_fromio(d + i * oob_chunk_size,
+ s + i * sparebuf_size,
+ mtd->oobsize - i * oob_chunk_size);
} else {
- for (i = 0; i < n - 1; i++)
- memcpy32_toio(&s[i * t], &d[i * j], j);
-
- /* the last section */
- memcpy32_toio(&s[i * t], &d[i * j], mtd->oobsize - i * j);
+ for (i = 0; i < num_chunks - 1; i++)
+ memcpy32_toio(&s[i * sparebuf_size],
+ &d[i * oob_chunk_size],
+ oob_chunk_size);
+
+ /* the last chunk */
+ memcpy32_toio(&s[oob_chunk_size * sparebuf_size],
+ &d[i * oob_chunk_size],
+ mtd->oobsize - i * oob_chunk_size);
}
}

--
2.1.4