[PATCH 17/39] mtd: nand: denali: support HW_ECC_FIXUP capability

[Masahiro Yamada <yamada.masahiro@socionext.com>]

Some old versions of the Denali IP (perhaps used only for Intel?)
detects ECC errors and provides correct data via a register, but
does not touch the transferred data.  So, the software must fixup
the data in the buffer according to the provided ECC correction
information.

Newer versions perform ECC correction before transferring the data.
No more software intervention is needed.  The ECC_ERROR_ADDRESS and
ECC_CORRECTION_INFO registers were deprecated.  Instead, the number
of corrected bit-flips can be read from the ECC_COR_INFO register.
When an uncorrectable ECC error happens, a status flag is set to the
INTR_STATUS and ECC_COR_INFO registers.

As is often the case with this IP, the register view of INTR_STATUS
had broken compatibility.

For older versions (SW ECC fixup):
  bit 0:  ECC_TRANSACTION_DONE
  bit 1:  ECC_ERR

For newer versions (HW ECC fixup):
  bit 0:  ECC_UNCOR_ERR
  bit 1:  Reserved

Due to this difference, the irq_mask must be fixed too.  The comment
block in the denali_sw_ecc_fixup() has been moved to the common part
because the comment applies to both cases.

The U-Boot port of this driver already supports the HW ECC fixup.  I
borrowed the comment "Some versions of ..." in denali.h from U-Boot.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 drivers/mtd/nand/denali.c | 44 ++++++++++++++++++++++++++++++++++----------
 drivers/mtd/nand/denali.h | 14 ++++++++++++++
 2 files changed, 48 insertions(+), 10 deletions(-)

diff --git a/drivers/mtd/nand/denali.c b/drivers/mtd/nand/denali.c
index 271b41a..c101e7f 100644
--- a/drivers/mtd/nand/denali.c
+++ b/drivers/mtd/nand/denali.c
@@ -894,6 +894,25 @@ static bool is_erased(u8 *buf, int len)
 			return false;
 	return true;
 }
+
+static bool denali_hw_ecc_fixup(struct denali_nand_info *denali,
+				unsigned int *max_bitflips)
+{
+	int bank = denali->flash_bank;
+	u32 ecc_cor;
+
+	ecc_cor = ioread32(denali->flash_reg + ECC_COR_INFO(bank));
+	ecc_cor >>= ECC_COR_INFO_SHIFT(bank);
+
+	if (ecc_cor & ECC_COR_INFO__UNCOR_ERR) {
+		*max_bitflips = 0;
+		return true;
+	}
+
+	*max_bitflips = ecc_cor & ECC_COR_INFO__MAX_ERRORS;
+	return false;
+}
+
 #define ECC_SECTOR_SIZE 512
 
 #define ECC_SECTOR(x)	(((x) & ECC_ERROR_ADDRESS__SECTOR_NR) >> 12)
@@ -949,11 +968,6 @@ static bool denali_sw_ecc_fixup(struct denali_nand_info *denali, u8 *buf,
 				bitflips++;
 			}
 		} else {
-			/*
-			 * if the error is not correctable, need to look at the
-			 * page to see if it is an erased page. if so, then
-			 * it's not a real ECC error
-			 */
 			check_erased_page = true;
 		}
 	} while (!ECC_LAST_ERR(err_correction_info));
@@ -1109,12 +1123,12 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
 {
 	unsigned int max_bitflips;
 	struct denali_nand_info *denali = mtd_to_denali(mtd);
-
 	dma_addr_t addr = denali->buf.dma_buf;
 	size_t size = mtd->writesize + mtd->oobsize;
-
 	u32 irq_status;
-	u32 irq_mask = INTR_STATUS__ECC_TRANSACTION_DONE | INTR_STATUS__ECC_ERR;
+	u32 irq_mask = denali->caps & DENALI_CAPS_HW_ECC_FIXUP ?
+		INTR_STATUS__DMA_CMD_COMP | INTR_STATUS__ECC_UNCOR_ERR :
+		INTR_STATUS__ECC_TRANSACTION_DONE | INTR_STATUS__ECC_ERR;
 	bool check_erased_page = false;
 
 	if (page != denali->page) {
@@ -1139,11 +1153,21 @@ static int denali_read_page(struct mtd_info *mtd, struct nand_chip *chip,
 
 	memcpy(buf, denali->buf.buf, mtd->writesize);
 
-	check_erased_page = denali_sw_ecc_fixup(denali, buf, irq_status,
-						&max_bitflips);
+	if (denali->caps & DENALI_CAPS_HW_ECC_FIXUP)
+		check_erased_page = denali_hw_ecc_fixup(denali, &max_bitflips);
+	else
+		check_erased_page = denali_sw_ecc_fixup(denali, buf, irq_status,
+							&max_bitflips);
+
 	denali_enable_dma(denali, false);
 
 	if (check_erased_page) {
+		/*
+		 * If the error is not correctable, need to look at the page to
+		 * see if it is an erased page. If so, then it's not a real ECC
+		 * error.
+		 */
+
 		read_oob_data(mtd, chip->oob_poi, denali->page);
 
 		/* check ECC failures that may have occurred on erased pages */
diff --git a/drivers/mtd/nand/denali.h b/drivers/mtd/nand/denali.h
index 69314d0..beadc8a 100644
--- a/drivers/mtd/nand/denali.h
+++ b/drivers/mtd/nand/denali.h
@@ -20,6 +20,7 @@
 #ifndef __DENALI_H__
 #define __DENALI_H__
 
+#include <linux/bitops.h>
 #include <linux/mtd/nand.h>
 
 #define DEVICE_RESET				0x0
@@ -219,6 +220,13 @@
 #define INTR_STATUS(__bank)	(0x410 + ((__bank) * 0x50))
 #define INTR_EN(__bank)		(0x420 + ((__bank) * 0x50))
 
+/*
+ * Some versions of the IP have the ECC fixup handled in hardware.  In this
+ * configuration we only get interrupted when the error is uncorrectable.
+ * Unfortunately this bit replaces INTR_STATUS__ECC_TRANSACTION_DONE from the
+ * old IP.
+ */
+#define     INTR_STATUS__ECC_UNCOR_ERR			0x0001
 #define     INTR_STATUS__ECC_TRANSACTION_DONE		0x0001
 #define     INTR_STATUS__ECC_ERR			0x0002
 #define     INTR_STATUS__DMA_CMD_COMP			0x0004
@@ -297,6 +305,11 @@
 #define     ERR_CORRECTION_INFO__ERROR_TYPE		0x4000
 #define     ERR_CORRECTION_INFO__LAST_ERR_INFO		0x8000
 
+#define ECC_COR_INFO(__bank)	(0x650 + (__bank) / 2 * 0x10)
+#define ECC_COR_INFO_SHIFT(__bank)	((__bank) % 2 * 8)
+#define     ECC_COR_INFO__MAX_ERRORS			0x007f
+#define     ECC_COR_INFO__UNCOR_ERR			0x0080
+
 #define DMA_ENABLE				0x700
 #define     DMA_ENABLE__FLAG				0x0001
 
@@ -421,6 +434,7 @@ struct denali_nand_info {
 	u32 bbtskipbytes;
 	u32 max_banks;
 	unsigned int caps;
+#define DENALI_CAPS_HW_ECC_FIXUP		BIT(0)
 };
 
 extern int denali_init(struct denali_nand_info *denali);
-- 
2.7.4