linux-kernel - Re: [PATCH v4 10/20] mtd: nand: qcom: erased codeword detection configuration

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Date:   Wed, 16 Aug 2017 10:14:30 +0530
From:   Archit Taneja <architt@...eaurora.org>
To:     Abhishek Sahu <absahu@...eaurora.org>,
        boris.brezillon@...e-electrons.com
Cc:     dwmw2@...radead.org, computersforpeace@...il.com,
        marek.vasut@...il.com, richard@....at, cyrille.pitchen@...ev4u.fr,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        andy.gross@...aro.org, sricharan@...eaurora.org
Subject: Re: [PATCH v4 10/20] mtd: nand: qcom: erased codeword detection
 configuration



On 08/11/2017 05:09 PM, Abhishek Sahu wrote:
> 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.

Reviewed-by: Archit Taneja <architt@...eaurora.org>

Thanks,
Archit

> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>   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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