2022-09-01 07:36:42

by Potthuri, Sai Krishna

Subject: [PATCH v2 2/2] mtd: spi-nor: Add support for flash reset

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 <[email protected]>
---
drivers/mtd/spi-nor/core.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index f2c64006f8d7..a78ab9bae2be 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -2933,6 +2933,27 @@ 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;
+
+ reset = devm_gpiod_get_optional(nor->dev, "reset", GPIOD_OUT_LOW);
+ if (IS_ERR_OR_NULL(reset))
+ return PTR_ERR_OR_ZERO(reset);
+
+ /*
+ * Experimental delay values by looking at different flash device
+ * vendors datasheets.
+ */
+ usleep_range(1, 5);
+ gpiod_set_value_cansleep(reset, 1);
+ usleep_range(100, 150);
+ gpiod_set_value_cansleep(reset, 0);
+ usleep_range(1000, 1200);
+
+ return 0;
+}
+
int spi_nor_scan(struct spi_nor *nor, const char *name,
const struct spi_nor_hwcaps *hwcaps)
{
@@ -2965,6 +2986,10 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
if (!nor->bouncebuf)
return -ENOMEM;

+ ret = spi_nor_hw_reset(nor);
+ if (ret)
+ return ret;
+
info = spi_nor_get_flash_info(nor, name);
if (IS_ERR(info))
return PTR_ERR(info);
--
2.17.1

2022-09-01 08:08:25

by Michael Walle

Subject: Re: [PATCH v2 2/2] mtd: spi-nor: Add support for flash reset

Am 2022-09-01 09:29, schrieb Sai Krishna Potthuri:
> 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 <[email protected]>

Reviewed-by: Michael Walle <[email protected]>

Just one comment, see below

> ---
> drivers/mtd/spi-nor/core.c | 25 +++++++++++++++++++++++++
> 1 file changed, 25 insertions(+)
>
> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> index f2c64006f8d7..a78ab9bae2be 100644
> --- a/drivers/mtd/spi-nor/core.c
> +++ b/drivers/mtd/spi-nor/core.c
> @@ -2933,6 +2933,27 @@ 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;
> +
> + reset = devm_gpiod_get_optional(nor->dev, "reset", GPIOD_OUT_LOW);
> + if (IS_ERR_OR_NULL(reset))
> + return PTR_ERR_OR_ZERO(reset);
> +
> + /*
> + * Experimental delay values by looking at different flash device
> + * vendors datasheets.
> + */
> + usleep_range(1, 5);

I think this is superfluous, because parts of the kernel
will boot which should take longer than 1us. But I'm
fine with leaving it here.

-michael

> + gpiod_set_value_cansleep(reset, 1);
> + usleep_range(100, 150);
> + gpiod_set_value_cansleep(reset, 0);
> + usleep_range(1000, 1200);
> +
> + return 0;
> +}
> +
> int spi_nor_scan(struct spi_nor *nor, const char *name,
> const struct spi_nor_hwcaps *hwcaps)
> {
> @@ -2965,6 +2986,10 @@ int spi_nor_scan(struct spi_nor *nor, const char
> *name,
> if (!nor->bouncebuf)
> return -ENOMEM;
>
> + ret = spi_nor_hw_reset(nor);
> + if (ret)
> + return ret;
> +
> info = spi_nor_get_flash_info(nor, name);
> if (IS_ERR(info))
> return PTR_ERR(info);