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Date:   Thu, 9 Jan 2020 17:51:07 +0100
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Mason Yang <masonccyang@mxic.com.tw>
Cc:     richard@nod.at, marek.vasut@gmail.com, dwmw2@infradead.org,
        bbrezillon@kernel.org, computersforpeace@gmail.com,
        vigneshr@ti.com, robh+dt@kernel.org, mark.rutland@arm.com,
        devicetree@vger.kernel.org, juliensu@mxic.com.tw,
        linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org
Subject: Re: [PATCH v4 1/2] mtd: rawnand: Add support for Macronix NAND
 randomizer
Message-ID: <20200109175107.57566c18@xps13>
In-Reply-To: <1571902807-10388-2-git-send-email-masonccyang@mxic.com.tw>
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        <1571902807-10388-2-git-send-email-masonccyang@mxic.com.tw>
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Hi Mason,

Mason Yang <masonccyang@mxic.com.tw> wrote on Thu, 24 Oct 2019 15:40:06
+0800:

> Macronix NANDs support randomizer operation for user data scrambled,
> which can be enabled with a SET_FEATURE.
> 
> User data written to the NAND device without randomizer is still readable
> after randomizer function enabled.
> The penalty of randomizer are subpage accesses prohibited and more time
> period is needed in program operation and entering deep power-down mode.
> i.e., tPROG 300us to 340us(randomizer enabled)
> 
> For more high-reliability concern, if subpage write not available with
> hardware ECC and then to enable randomizer is recommended by default.
> Driver checks byte 167 of Vendor Blocks in ONFI parameter page table
> to see if this high-reliability function is supported. By adding a new
> specific DT property in children nodes to enable randomizer function.
> 
> Signed-off-by: Mason Yang <masonccyang@mxic.com.tw>
> ---
>  drivers/mtd/nand/raw/nand_macronix.c | 69 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 69 insertions(+)
> 
> diff --git a/drivers/mtd/nand/raw/nand_macronix.c b/drivers/mtd/nand/raw/nand_macronix.c
> index 58511ae..89101fa 100644
> --- a/drivers/mtd/nand/raw/nand_macronix.c
> +++ b/drivers/mtd/nand/raw/nand_macronix.c
> @@ -11,6 +11,14 @@
>  #define MACRONIX_READ_RETRY_BIT BIT(0)
>  #define MACRONIX_NUM_READ_RETRY_MODES 6
>  
> +#define MACRONIX_RANDOMIZER_BIT BIT(1)
> +#define ONFI_FEATURE_ADDR_MXIC_RANDOMIZER 0xB0
> +#define ENPGM BIT(0)
> +#define RANDEN BIT(1)
> +#define RANDOPT BIT(2)

I forgot: please be consistent with the naming.

Thanks,
Miquèl