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

[Potthuri, Sai Krishna]

Hi Takahiro Kuwano,

> -----Original Message-----
> From: Takahiro Kuwano <tkuw584924 at gmail.com>
> Sent: Thursday, September 1, 2022 7:28 AM
> To: Potthuri, Sai Krishna <sai.krishna.potthuri at amd.com>; Tudor Ambarus
> <tudor.ambarus at microchip.com>; Pratyush Yadav <pratyush at kernel.org>;
> Michael Walle <michael at walle.cc>; Miquel Raynal
> <miquel.raynal at bootlin.com>; Richard Weinberger <richard at nod.at>;
> Vignesh Raghavendra <vigneshr at ti.com>; Rob Herring
> <robh+dt at kernel.org>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt at linaro.org>
> Cc: devicetree at vger.kernel.org; linux-mtd at lists.infradead.org; linux-
> kernel at vger.kernel.org; saikrishna12468 at gmail.com; git (AMD-Xilinx)
> <git at amd.com>; takahiro Kuwano <Takahiro.Kuwano at infineon.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 at amd.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 for sharing this information.
I will take care of this in v2.

Regards
Sai Krishna