[PATCH 2/2] mxc_nand: use our own read_page function

[Michael Grzeschik <m.grzeschik@pengutronix.de>]

The current approach of the read_page function is to iterate over all
subpages and call the correct_data function. The correct_data function
currently does the same. It iterates over all subpages and checks for
correctable and uncorrectable data. This redundant call for each
subpage leads to miscalculations.

This patch changes the driver to use its own read_page function in which
we call the correct_data function only once per page. With that we do
the failure and correct statistics counting inside this function.

Signed-off-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
---
 drivers/mtd/nand/mxc_nand.c | 73 ++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 69 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
index 7fd495e..09e3682 100644
--- a/drivers/mtd/nand/mxc_nand.c
+++ b/drivers/mtd/nand/mxc_nand.c
@@ -141,6 +141,8 @@ struct mxc_nand_host;
 
 struct mxc_nand_devtype_data {
 	void (*preset)(struct mtd_info *);
+	int (*read_page)(struct mtd_info *mtd, struct nand_chip *chip,
+			uint8_t *buf, int oob_required, int page);
 	void (*send_cmd)(struct mxc_nand_host *, uint16_t, int);
 	void (*send_addr)(struct mxc_nand_host *, uint16_t, int);
 	void (*send_page)(struct mtd_info *, unsigned int);
@@ -649,6 +651,59 @@ static int mxc_nand_correct_data_v1(struct mtd_info *mtd, u_char *dat,
 	return 0;
 }
 
+/**
+ * mxc_nand_read_page_hwecc_v2_v3 - [REPLACEABLE] hardware ECC based page read function
+ * @mtd: mtd info structure
+ * @chip: nand chip info structure
+ * @buf: buffer to store read data
+ * @oob_required: caller requires OOB data read to chip->oob_poi
+ * @page: page number to read
+ *
+ * Not for syndrome calculating ECC controllers which need a special oob layout.
+ */
+static int
+mxc_nand_read_page_hwecc_v2_v3(struct mtd_info *mtd,
+			       struct nand_chip *chip,
+			       uint8_t *buf, int oob_required, int page)
+{
+	int i, eccsize = chip->ecc.size;
+	struct nand_chip *nand_chip = mtd->priv;
+	struct mxc_nand_host *host = nand_chip->priv;
+	int eccbytes = chip->ecc.bytes;
+	int eccsteps = chip->ecc.steps;
+	uint8_t *p = buf;
+	uint8_t *ecc_calc = chip->buffers->ecccalc;
+	uint8_t *ecc_code = chip->buffers->ecccode;
+	uint32_t *eccpos = chip->ecc.layout->eccpos;
+	unsigned int max_bitflips = 0;
+	u32 ecc_stat, err;
+	int stat;
+
+	ecc_stat = host->devtype_data->get_ecc_status(host);
+	for (i = 0; eccsteps; eccsteps--, i += eccbytes, p += eccsize) {
+		err = ecc_stat & 0xf;
+		chip->ecc.hwctl(mtd, NAND_ECC_READ);
+		chip->read_buf(mtd, p, eccsize);
+		chip->ecc.calculate(mtd, p, &ecc_calc[i]);
+		ecc_stat >>= 4;
+
+	}
+	ecc_stat = host->devtype_data->get_ecc_status(host);
+	chip->read_buf(mtd, chip->oob_poi, mtd->oobsize);
+
+	for (i = 0; i < chip->ecc.total; i++)
+		ecc_code[i] = chip->oob_poi[eccpos[i]];
+
+	eccsteps = chip->ecc.steps;
+	p = buf;
+
+	stat = chip->ecc.correct(mtd, p, &ecc_code[i], &ecc_calc[i]);
+	max_bitflips = max_t(unsigned int, max_bitflips, stat);
+
+	return max_bitflips;
+}
+
+
 static int mxc_nand_correct_data_v2_v3(struct mtd_info *mtd, u_char *dat,
 				 u_char *read_ecc, u_char *calc_ecc)
 {
@@ -656,7 +711,7 @@ static int mxc_nand_correct_data_v2_v3(struct mtd_info *mtd, u_char *dat,
 	struct mxc_nand_host *host = nand_chip->priv;
 	u32 ecc_stat, err;
 	int no_subpages = 1;
-	int ret = 0;
+	int ret = 0, broken = 0;
 	u8 ecc_bit_mask, err_limit = 0x1;
 
 	ecc_bit_mask = 0xf;
@@ -673,15 +728,21 @@ static int mxc_nand_correct_data_v2_v3(struct mtd_info *mtd, u_char *dat,
 	do {
 		err = ecc_stat & ecc_bit_mask;
 		if (err > err_limit) {
-			printk(KERN_WARNING "UnCorrectable RS-ECC Error\n");
-			return -1;
+			broken++;
 		} else {
 			ret += err;
 		}
 		ecc_stat >>= 4;
 	} while (--no_subpages);
 
-	pr_debug("%d Symbol Correctable RS-ECC Error\n", ret);
+	mtd->ecc_stats.corrected += ret;
+	if (ret)
+		printk("%d Symbol Correctable RS-ECC Error\n", ret);
+
+	mtd->ecc_stats.failed += broken;
+	if (broken)
+		printk(KERN_WARNING "%d Symbol UnCorrectable RS-ECC Error\n",
+			 broken);
 
 	return ret;
 }
@@ -1244,6 +1305,7 @@ static const struct mxc_nand_devtype_data imx27_nand_devtype_data = {
 /* v21: i.MX25, i.MX35 */
 static const struct mxc_nand_devtype_data imx25_nand_devtype_data = {
 	.preset = preset_v2,
+	.read_page = mxc_nand_read_page_hwecc_v2_v3,
 	.send_cmd = send_cmd_v1_v2,
 	.send_addr = send_addr_v1_v2,
 	.send_page = send_page_v2,
@@ -1270,6 +1332,7 @@ static const struct mxc_nand_devtype_data imx25_nand_devtype_data = {
 /* v3.2a: i.MX51 */
 static const struct mxc_nand_devtype_data imx51_nand_devtype_data = {
 	.preset = preset_v3,
+	.read_page = mxc_nand_read_page_hwecc_v2_v3,
 	.send_cmd = send_cmd_v3,
 	.send_addr = send_addr_v3,
 	.send_page = send_page_v3,
@@ -1297,6 +1360,7 @@ static const struct mxc_nand_devtype_data imx51_nand_devtype_data = {
 /* v3.2b: i.MX53 */
 static const struct mxc_nand_devtype_data imx53_nand_devtype_data = {
 	.preset = preset_v3,
+	.read_page = mxc_nand_read_page_hwecc_v2_v3,
 	.send_cmd = send_cmd_v3,
 	.send_addr = send_addr_v3,
 	.send_page = send_page_v3,
@@ -1517,6 +1581,7 @@ static int mxcnd_probe(struct platform_device *pdev)
 	this->ecc.layout = host->devtype_data->ecclayout_512;
 
 	if (host->pdata.hw_ecc) {
+		this->ecc.read_page = host->devtype_data->read_page;
 		this->ecc.calculate = mxc_nand_calculate_ecc;
 		this->ecc.hwctl = mxc_nand_enable_hwecc;
 		this->ecc.correct = host->devtype_data->correct_data;
-- 
2.0.0