linux-kernel - Re: [PATCH V1 1/1] mtd: mtk-nor: set controller to 4B mode with large capacity flash

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Date:   Thu, 30 Mar 2017 12:00:27 +0200
From:   Marek Vasut <marek.vasut@...il.com>
To:     Guochun Mao <guochun.mao@...iatek.com>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Richard Weinberger <richard@....at>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Russell King <linux@...linux.org.uk>,
        linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1 1/1] mtd: mtk-nor: set controller to 4B mode with large
 capacity flash

On 03/30/2017 10:23 AM, Guochun Mao wrote:
> when nor's size larger than 16MByte, nor and controller should
> enter 4Byte mode simultaneously.
> 
> Signed-off-by: Guochun Mao <guochun.mao@...iatek.com>
> ---
>  drivers/mtd/spi-nor/mtk-quadspi.c |    7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/mtd/spi-nor/mtk-quadspi.c b/drivers/mtd/spi-nor/mtk-quadspi.c
> index e661877..05cd8a8 100644
> --- a/drivers/mtd/spi-nor/mtk-quadspi.c
> +++ b/drivers/mtd/spi-nor/mtk-quadspi.c
> @@ -369,6 +369,13 @@ static int mt8173_nor_write_reg(struct spi_nor *nor, u8 opcode, u8 *buf,
>  		/* We only handle 1 byte */
>  		ret = mt8173_nor_wr_sr(mt8173_nor, *buf);
>  		break;
> +	case SPINOR_OP_EN4B:
> +		/* Set nor controller to 4-byte address mode,
> +		 * and simultaneously set nor flash.
> +		 * This case should cooperate with default operation.
> +		 */
> +		writeb(readb(mt8173_nor->base + MTK_NOR_DUAL_REG) | 0x10,
> +				mt8173_nor->base + MTK_NOR_DUAL_REG);

And what happens on READ then ? Who clears that bit when protocol
changes ? You probably want something like cqspi_set_protocol()
instead, which is invoked from {read,write}{,_reg}() and erase().

>  	default:
>  		ret = mt8173_nor_do_tx_rx(mt8173_nor, opcode, buf, len, NULL, 0);
>  		if (ret)
> 


-- 
Best regards,
Marek Vasut