[PATCH v4 10/20] mtd: nand: qcom: erased codeword detection configuration

[Abhishek Sahu]

The NAND controller returns ECC failure during read of completely
erased codeword. The NAND controller has hardware functionality
to detect erased codeword in case of BCH ECC algorithm. The
NAND_ERASED_CW_DETECT_CFG register controls the erased
codeword/page detection controller. This register should be reset
before every page read by setting and clearing bit 0 of
NAND_ERASED_CW_DETECT_CFG.

Signed-off-by: Abhishek Sahu <absahu@xxxxxxxxxxxxxx>
---
 drivers/mtd/nand/qcom_nandc.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
index b452cfb..3d9fd7f 100644
--- a/drivers/mtd/nand/qcom_nandc.c
+++ b/drivers/mtd/nand/qcom_nandc.c
@@ -200,6 +200,11 @@
 #define NAND_BAM_NWD			BIT(1)
 /* Finish writing in the current sgl and start writing in another sgl */
 #define NAND_BAM_NEXT_SGL		BIT(2)
+/*
+ * Erased codeword status is being used two times in single transfer so this
+ * flag will determine the current value of erased codeword status register
+ */
+#define NAND_ERASED_CW_SET		BIT(4)
 
 /*
  * This data type corresponds to the BAM transaction which will be used for all
@@ -278,6 +283,8 @@ struct nandc_regs {
 	__le32 read_location2;
 	__le32 read_location3;
 
+	__le32 erased_cw_detect_cfg_clr;
+	__le32 erased_cw_detect_cfg_set;
 };
 
 /*
@@ -805,6 +812,13 @@ static int write_reg_dma(struct qcom_nand_controller *nandc, int first,
 	if (first == NAND_FLASH_CMD)
 		flow_control = true;
 
+	if (first == NAND_ERASED_CW_DETECT_CFG) {
+		if (flags & NAND_ERASED_CW_SET)
+			vaddr = &regs->erased_cw_detect_cfg_set;
+		else
+			vaddr = &regs->erased_cw_detect_cfg_clr;
+	}
+
 	if (first == NAND_EXEC_CMD)
 		flags |= NAND_BAM_NWD;
 
@@ -857,6 +871,9 @@ static void config_nand_page_read(struct qcom_nand_controller *nandc)
 	write_reg_dma(nandc, NAND_ADDR0, 2, 0);
 	write_reg_dma(nandc, NAND_DEV0_CFG0, 3, 0);
 	write_reg_dma(nandc, NAND_EBI2_ECC_BUF_CFG, 1, 0);
+	write_reg_dma(nandc, NAND_ERASED_CW_DETECT_CFG, 1, 0);
+	write_reg_dma(nandc, NAND_ERASED_CW_DETECT_CFG, 1,
+		      NAND_ERASED_CW_SET | NAND_BAM_NEXT_SGL);
 }
 
 /*
@@ -2258,6 +2275,10 @@ static int qcom_nand_host_setup(struct qcom_nand_host *host)
 
 	host->clrflashstatus = FS_READY_BSY_N;
 	host->clrreadstatus = 0xc0;
+	nandc->regs->erased_cw_detect_cfg_clr =
+		cpu_to_le32(CLR_ERASED_PAGE_DET);
+	nandc->regs->erased_cw_detect_cfg_set =
+		cpu_to_le32(SET_ERASED_PAGE_DET);
 
 	dev_dbg(nandc->dev,
 		"cfg0 %x cfg1 %x ecc_buf_cfg %x ecc_bch cfg %x cw_size %d cw_data %d strength %d parity_bytes %d steps %d\n",
-- 
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