linux-kernel - Re: [PATCH 2/2] mtd: spi-nor: Add support for flash reset

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Message-ID: <11077b0e-0a79-401e-5232-1dc1d1a04d83@gmail.com>
Date:   Thu, 1 Sep 2022 10:57:36 +0900
From:   Takahiro Kuwano <tkuw584924@...il.com>
To:     Sai Krishna Potthuri <sai.krishna.potthuri@....com>,
        Tudor Ambarus <tudor.ambarus@...rochip.com>,
        Pratyush Yadav <pratyush@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Cc:     devicetree@...r.kernel.org, linux-mtd@...ts.infradead.org,
        linux-kernel@...r.kernel.org, saikrishna12468@...il.com,
        git@....com, takahiro Kuwano <Takahiro.Kuwano@...ineon.com>
Subject: Re: [PATCH 2/2] mtd: spi-nor: Add support for flash reset

Hello,

On 8/29/2022 6:05 PM, Sai Krishna Potthuri wrote:
> Add support for spi-nor flash reset via GPIO controller by reading the
> reset-gpio property. If there is a valid GPIO specifier then reset will
> be performed by asserting and deasserting the GPIO using gpiod APIs
> otherwise it will not perform any operation.
> 
> Signed-off-by: Sai Krishna Potthuri <sai.krishna.potthuri@....com>
> ---
>  drivers/mtd/spi-nor/core.c | 50 +++++++++++++++++++++++++++++++++++---
>  1 file changed, 46 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index f2c64006f8d7..d4703ff69ad0 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2401,12 +2401,8 @@ static void spi_nor_no_sfdp_init_params(struct spi_nor *nor)
>   */
>  static void spi_nor_init_flags(struct spi_nor *nor)
>  {
> -	struct device_node *np = spi_nor_get_flash_node(nor);
>  	const u16 flags = nor->info->flags;
>  
> -	if (of_property_read_bool(np, "broken-flash-reset"))
> -		nor->flags |= SNOR_F_BROKEN_RESET;
> -
>  	if (flags & SPI_NOR_SWP_IS_VOLATILE)
>  		nor->flags |= SNOR_F_SWP_IS_VOLATILE;
>  
> @@ -2933,9 +2929,47 @@ static void spi_nor_set_mtd_info(struct spi_nor *nor)
>  	mtd->_put_device = spi_nor_put_device;
>  }
>  
> +static int spi_nor_hw_reset(struct spi_nor *nor)
> +{
> +	struct gpio_desc *reset;
> +	int ret;
> +
> +	reset = devm_gpiod_get_optional(nor->dev, "reset", GPIOD_ASIS);
> +	if (IS_ERR_OR_NULL(reset))
> +		return PTR_ERR_OR_ZERO(reset);
> +
> +	/* Set the direction as output and enable the output */
> +	ret = gpiod_direction_output(reset, 1);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Experimental Minimum Chip select high to Reset delay value
> +	 * based on the flash device spec.
> +	 */
> +	usleep_range(1, 5);
> +	gpiod_set_value(reset, 0);
> +
> +	/*
> +	 * Experimental Minimum Reset pulse width value based on the
> +	 * flash device spec.
> +	 */
> +	usleep_range(10, 15);
> +	gpiod_set_value(reset, 1);
> +
> +	/*
> +	 * Experimental Minimum Reset recovery delay value based on the
> +	 * flash device spec.
> +	 */
> +	usleep_range(35, 40);
Infineon (Spansion/Cypress) SEMPER flash (S25HL/HS, S28HL/HS) family
specifies minimum tRH (Reset Pulse Hold - RESET# Low to CS# Low) as
450~600us. Please take care for this.

Please find datasheets at the following links.

https://www.infineon.com/dgdl/Infineon-S25HS256T_S25HS512T_S25HS01GT_S25HL256T_S25HL512T_S25HL01GT_256-Mb_(32-MB)_512-Mb_(64-MB)_1-Gb_(128-MB)_HS-T_(1.8-V)_HL-T_(3.0-V)_Semper_Flash_with_Quad_SPI-DataSheet-v02_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ee674b86ee3&da=t

https://www.infineon.com/dgdl/Infineon-S28HS256T_S28HS512T_S28HS01GT_S28HL256T_S28HL512T_S28HL01GT_256-Mb_(32-MB)_512-Mb_(64-MB)_1-Gb_(128-MB)_HS-T_(1.8-V)_HL-T_(3.0-V)_Semper_Flash_with_Octal_Interface-DataSheet-v03_00-EN.pdf?fileId=8ac78c8c7d0d8da4017d0ee6bca96f97&da=t

Thanks,
Takahiro Kuwano