linux-kernel - Re: [PATCH 11/13] mtd: spinand: Add support for Power-on-Reset (PoR) instruction

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Date:   Fri, 6 Aug 2021 21:08:40 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Apurva Nandan <a-nandan@...com>
Cc:     Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Mark Brown <broonie@...nel.org>,
        Patrice Chotard <patrice.chotard@...s.st.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-spi@...r.kernel.org>, Pratyush Yadav <p.yadav@...com>
Subject: Re: [PATCH 11/13] mtd: spinand: Add support for Power-on-Reset
 (PoR) instruction

Hi Apurva,

Apurva Nandan <a-nandan@...com> wrote on Tue, 13 Jul 2021 13:05:36
+0000:

> Manufacturers like Gigadevice and Winbond are adding Power-on-Reset
> functionality in their SPI NAND flash chips. PoR instruction consists
> of a 66h command followed by 99h command, and is different from the FFh
> reset. The reset command FFh just clears the status only registers,
> while the PoR command erases all the configurations written to the
> flash and is equivalent to a power-down -> power-up cycle.
> 
> Add support for the Power-on-Reset command for any flash that provides
> this feature.
> 
> Datasheet: https://www.winbond.com/export/sites/winbond/datasheet/W35N01JW_Datasheet_Brief.pdf
> 
> Signed-off-by: Apurva Nandan <a-nandan@...com>
> ---

[...]
				\
> @@ -218,6 +230,8 @@ struct spinand_device;
>   * reading/programming/erasing when the RESET occurs. Since we always
>   * issue a RESET when the device is IDLE, 5us is selected for both initial
>   * and poll delay.
> + * Power on Reset can take max upto 500 us to complete, so sleep for 1000 us

s/max upto/up to/

> + * to 1200 us safely.

I don't really get why, if the maximum is 500, then let's wait for
500us.

>   */
>  #define SPINAND_READ_INITIAL_DELAY_US	6
>  #define SPINAND_READ_POLL_DELAY_US	5
> @@ -227,6 +241,8 @@ struct spinand_device;
>  #define SPINAND_WRITE_POLL_DELAY_US	15
>  #define SPINAND_ERASE_INITIAL_DELAY_US	250
>  #define SPINAND_ERASE_POLL_DELAY_US	50
> +#define SPINAND_POR_MIN_DELAY_US	1000
> +#define SPINAND_POR_MAX_DELAY_US	1200
>  
>  #define SPINAND_WAITRDY_TIMEOUT_MS	400
>  
> @@ -351,6 +367,7 @@ struct spinand_ecc_info {
>  #define SPINAND_HAS_QE_BIT		BIT(0)
>  #define SPINAND_HAS_CR_FEAT_BIT		BIT(1)
>  #define SPINAND_HAS_OCTAL_DTR_BIT	BIT(2)
> +#define SPINAND_HAS_POR_CMD_BIT		BIT(3)
>  
>  /**
>   * struct spinand_ondie_ecc_conf - private SPI-NAND on-die ECC engine structure




Thanks,
Miquèl