linux-kernel - Re: [PATCH v4 11/20] mtd: nand: qcom: enable BAM or ADM mode

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Date:   Wed, 16 Aug 2017 10:20:15 +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 11/20] mtd: nand: qcom: enable BAM or ADM mode



On 08/11/2017 05:09 PM, Abhishek Sahu wrote:
> 1. DM_EN is only required for EBI2 NAND controller which uses ADM
> 2. BAM mode will be disabled after power on reset which needs to
>     be enabled before starting any BAM transfers.
> 
> Signed-off-by: Abhishek Sahu <absahu@...eaurora.org>
> ---
>   drivers/mtd/nand/qcom_nandc.c | 17 ++++++++++++++---
>   1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/qcom_nandc.c b/drivers/mtd/nand/qcom_nandc.c
> index 3d9fd7f..ae873d3 100644
> --- a/drivers/mtd/nand/qcom_nandc.c
> +++ b/drivers/mtd/nand/qcom_nandc.c
> @@ -163,6 +163,9 @@
>   #define NAND_DEV_CMD_VLD_VAL		(READ_START_VLD | WRITE_START_VLD | \
>   					 ERASE_START_VLD | SEQ_READ_START_VLD)
>   
> +/* NAND_CTRL bits */
> +#define	BAM_MODE_EN			BIT(0)
> +
>   /*
>    * the NAND controller performs reads/writes with ECC in 516 byte chunks.
>    * the driver calls the chunks 'step' or 'codeword' interchangeably
> @@ -1035,7 +1038,8 @@ static int read_id(struct qcom_nand_host *host, int column)
>   	nandc_set_reg(nandc, NAND_FLASH_CMD, FETCH_ID);
>   	nandc_set_reg(nandc, NAND_ADDR0, column);
>   	nandc_set_reg(nandc, NAND_ADDR1, 0);
> -	nandc_set_reg(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
> +	nandc_set_reg(nandc, NAND_FLASH_CHIP_SELECT,
> +		      nandc->props->is_bam ? 0 : DM_EN);

I'm not sure why the above register was configured in read_id in the first place. Would
it be required later if we want the controller to support multiple NAND chips? If not,
then we could consider dropping this. Anyway, that can be posted as a separate patch
later.

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

Thanks,
Archit

>   	nandc_set_reg(nandc, NAND_EXEC_CMD, 1);
>   
>   	write_reg_dma(nandc, NAND_FLASH_CMD, 4, NAND_BAM_NEXT_SGL);
> @@ -2408,12 +2412,19 @@ static void qcom_nandc_unalloc(struct qcom_nand_controller *nandc)
>   /* one time setup of a few nand controller registers */
>   static int qcom_nandc_setup(struct qcom_nand_controller *nandc)
>   {
> +	u32 nand_ctrl;
> +
>   	/* kill onenand */
>   	nandc_write(nandc, SFLASHC_BURST_CFG, 0);
>   	nandc_write(nandc, NAND_DEV_CMD_VLD, NAND_DEV_CMD_VLD_VAL);
>   
> -	/* enable ADM DMA */
> -	nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
> +	/* enable ADM or BAM DMA */
> +	if (nandc->props->is_bam) {
> +		nand_ctrl = nandc_read(nandc, NAND_CTRL);
> +		nandc_write(nandc, NAND_CTRL, nand_ctrl | BAM_MODE_EN);
> +	} else {
> +		nandc_write(nandc, NAND_FLASH_CHIP_SELECT, DM_EN);
> +	}
>   
>   	/* save the original values of these registers */
>   	nandc->cmd1 = nandc_read(nandc, NAND_DEV_CMD1);
> 

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