mtd: nand: pxa3xx: Add driver-specific ECC BCH support

This commit adds the BCH ECC support available in NFCv2 controller.
Depending on the detected required strength the respective ECC layout
is selected.

This commit adds an empty ECC layout, since support to access large
pages is first required. Once that support is added, a proper ECC
layout will be added as well.

Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Tested-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/pxa3xx_nand.c

@@ -58,6 +58,7 @@
 #define NDPCR		(0x18) /* Page Count Register */
 #define NDBDR0		(0x1C) /* Bad Block Register 0 */
 #define NDBDR1		(0x20) /* Bad Block Register 1 */
+#define NDECCCTRL	(0x28) /* ECC control */
 #define NDDB		(0x40) /* Data Buffer */
 #define NDCB0		(0x48) /* Command Buffer0 */
 #define NDCB1		(0x4C) /* Command Buffer1 */
@@ -198,6 +199,7 @@ struct pxa3xx_nand_info {
 
 	int			cs;
 	int			use_ecc;	/* use HW ECC ? */
+	int			ecc_bch;	/* using BCH ECC? */
 	int			use_dma;	/* use DMA ? */
 	int			use_spare;	/* use spare ? */
 	int			need_wait;
@@ -205,6 +207,8 @@ struct pxa3xx_nand_info {
 	unsigned int		fifo_size;	/* max. data size in the FIFO */
 	unsigned int		data_size;	/* data to be read from FIFO */
 	unsigned int		oob_size;
+	unsigned int		spare_size;
+	unsigned int		ecc_size;
 	int 			retcode;
 
 	/* cached register value */
@@ -335,19 +339,12 @@ static void pxa3xx_set_datasize(struct pxa3xx_nand_info *info)
 	int oob_enable = info->reg_ndcr & NDCR_SPARE_EN;
 
 	info->data_size = info->fifo_size;
-	if (!oob_enable) {
-		info->oob_size = 0;
+	if (!oob_enable)
 		return;
-	}
 
-	switch (info->fifo_size) {
-	case 2048:
-		info->oob_size = (info->use_ecc) ? 40 : 64;
-		break;
-	case 512:
-		info->oob_size = (info->use_ecc) ? 8 : 16;
-		break;
-	}
+	info->oob_size = info->spare_size;
+	if (!info->use_ecc)
+		info->oob_size += info->ecc_size;
 }
 
 /**
@@ -362,10 +359,15 @@ static void pxa3xx_nand_start(struct pxa3xx_nand_info *info)
 
 	ndcr = info->reg_ndcr;
 
-	if (info->use_ecc)
+	if (info->use_ecc) {
 		ndcr |= NDCR_ECC_EN;
-	else
+		if (info->ecc_bch)
+			nand_writel(info, NDECCCTRL, 0x1);
+	} else {
 		ndcr &= ~NDCR_ECC_EN;
+		if (info->ecc_bch)
+			nand_writel(info, NDECCCTRL, 0x0);
+	}
 
 	if (info->use_dma)
 		ndcr |= NDCR_DMA_EN;
@@ -1067,6 +1069,41 @@ static int pxa3xx_nand_sensing(struct pxa3xx_nand_info *info)
 	return 0;
 }
 
+static int pxa_ecc_init(struct pxa3xx_nand_info *info,
+			struct nand_ecc_ctrl *ecc,
+			int strength, int page_size)
+{
+	/*
+	 * We don't use strength here as the PXA variant
+	 * is used with non-ONFI compliant devices.
+	 */
+	if (page_size == 2048) {
+		info->spare_size = 40;
+		info->ecc_size = 24;
+		ecc->mode = NAND_ECC_HW;
+		ecc->size = 512;
+		ecc->strength = 1;
+		return 1;
+
+	} else if (page_size == 512) {
+		info->spare_size = 8;
+		info->ecc_size = 8;
+		ecc->mode = NAND_ECC_HW;
+		ecc->size = 512;
+		ecc->strength = 1;
+		return 1;
+	}
+	return 0;
+}
+
+static int armada370_ecc_init(struct pxa3xx_nand_info *info,
+			      struct nand_ecc_ctrl *ecc,
+			      int strength, int page_size)
+{
+	/* Unimplemented yet */
+	return 0;
+}
+
 static int pxa3xx_nand_scan(struct mtd_info *mtd)
 {
 	struct pxa3xx_nand_host *host = mtd->priv;
@@ -1137,13 +1174,13 @@ static int pxa3xx_nand_scan(struct mtd_info *mtd)
 	pxa3xx_flash_ids[1].name = NULL;
 	def = pxa3xx_flash_ids;
 KEEP_CONFIG:
-	chip->ecc.mode = NAND_ECC_HW;
-	chip->ecc.size = info->fifo_size;
-	chip->ecc.strength = 1;
-
 	if (info->reg_ndcr & NDCR_DWIDTH_M)
 		chip->options |= NAND_BUSWIDTH_16;
 
+	/* Device detection must be done with ECC disabled */
+	if (info->variant == PXA3XX_NAND_VARIANT_ARMADA370)
+		nand_writel(info, NDECCCTRL, 0x0);
+
 	if (nand_scan_ident(mtd, 1, def))
 		return -ENODEV;
 
@@ -1158,6 +1195,21 @@ KEEP_CONFIG:
 		chip->bbt_md = &bbt_mirror_descr;
 	}
 
+	if (info->variant == PXA3XX_NAND_VARIANT_ARMADA370)
+		ret = armada370_ecc_init(info, &chip->ecc,
+				   chip->ecc_strength_ds,
+				   mtd->writesize);
+	else
+		ret = pxa_ecc_init(info, &chip->ecc,
+				   chip->ecc_strength_ds,
+				   mtd->writesize);
+	if (!ret) {
+		dev_err(&info->pdev->dev,
+			"ECC strength %d at page size %d is not supported\n",
+			chip->ecc_strength_ds, mtd->writesize);
+		return -ENODEV;
+	}
+
 	/* calculate addressing information */
 	if (mtd->writesize >= 2048)
 		host->col_addr_cycles = 2;