linux-kernel - Re: [PATCH 12/13] mtd: spinand: Perform Power-on-Reset when runtime

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Date:   Fri, 6 Aug 2021 21:12:31 +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 12/13] mtd: spinand: Perform Power-on-Reset when
 runtime_pm suspend is issued

Hi Apurva,

Apurva Nandan <a-nandan@...com> wrote on Tue, 13 Jul 2021 13:05:37
+0000:

> A soft reset using FFh command doesn't erase the flash's configuration
> and doesn't reset the SPI IO mode also. This can result in the flash
> being in a different SPI IO mode, e.g. Octal DTR, when resuming from
> sleep. This would render the flash in an unusable state.

              could put the falsh in?

> Perform a Power-on-Reset (PoR), if available in the flash, when
> suspending the device by runtime_pm. This would set the flash to clean

I think runtime_pm is something else.

> state for reinitialization during resume and would also ensure that it
> is in standard SPI IO mode (1S-1S-1S) before the resume begins.

Please add a comment about this to explain why we don't do this reset
at resume time.

> 
> Signed-off-by: Apurva Nandan <a-nandan@...com>
> ---
>  drivers/mtd/nand/spi/core.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
> index 608f4eb85b0a..6fb3aa6af540 100644
> --- a/drivers/mtd/nand/spi/core.c
> +++ b/drivers/mtd/nand/spi/core.c
> @@ -1329,6 +1329,21 @@ static void spinand_mtd_resume(struct mtd_info *mtd)
>  	spinand_ecc_enable(spinand, false);
>  }
>  
> +static int spinand_mtd_suspend(struct mtd_info *mtd)
> +{
> +	struct spinand_device *spinand = mtd_to_spinand(mtd);
> +	int ret;
> +
> +	if (!(spinand->flags & SPINAND_HAS_POR_CMD_BIT))
> +		return 0;
> +
> +	ret = spinand_power_on_rst_op(spinand);
> +	if (ret)
> +		dev_err(&spinand->spimem->spi->dev, "suspend() failed\n");
> +
> +	return ret;
> +}
> +
>  static int spinand_init(struct spinand_device *spinand)
>  {
>  	struct device *dev = &spinand->spimem->spi->dev;
> @@ -1401,6 +1416,7 @@ static int spinand_init(struct spinand_device *spinand)
>  	mtd->_erase = spinand_mtd_erase;
>  	mtd->_max_bad_blocks = nanddev_mtd_max_bad_blocks;
>  	mtd->_resume = spinand_mtd_resume;
> +	mtd->_suspend = spinand_mtd_suspend;
>  
>  	if (nand->ecc.engine) {
>  		ret = mtd_ooblayout_count_freebytes(mtd);


Thanks,
Miquèl