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

[Venkatesh Yadav Abbarapu]

Add support for spi-nor flash reset via GPIO controller
by reading the reset-gpios property.

[Ported from Linux kernel commit
8f1ee9ef71d0 ("mtd: spi-nor: Add support for flash reset") ]

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu at amd.com>
---
Changes in v2:
- Removed the code from spi_nor_remove() as gpio descriptor is
managed by DEVRES.
---
 drivers/mtd/spi/spi-nor-core.c | 38 ++++++++++++++++++++++++++++++++++
 include/linux/mtd/spi-nor.h    |  1 +
 2 files changed, 39 insertions(+)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index ec841fb13b..93a7d046c0 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -12,6 +12,7 @@
 #include <display_options.h>
 #include <log.h>
 #include <watchdog.h>
+#include <asm/gpio.h>
 #include <dm.h>
 #include <dm/device_compat.h>
 #include <dm/devres.h>
@@ -4415,6 +4416,37 @@ void spi_nor_set_fixups(struct spi_nor *nor)
 #endif /* SPI_FLASH_MACRONIX */
 }
 
+static int spi_nor_hw_reset(struct spi_nor *nor)
+{
+	struct udevice *dev = nor->spi->dev;
+	int rc;
+
+	nor->flash_gpio_reset = devm_gpiod_get_optional(dev, "reset",
+							GPIOD_IS_OUT | GPIOD_ACTIVE_LOW);
+
+	if (nor->flash_gpio_reset) {
+		/*
+		 * Experimental delay values by looking at different flash device
+		 * vendors datasheets.
+		 */
+		udelay(5);
+
+		/* Toggle gpio to reset the flash device. */
+		rc = dm_gpio_set_value(nor->flash_gpio_reset, 1);
+		if (rc)
+			return rc;
+
+		udelay(150);
+
+		rc = dm_gpio_set_value(nor->flash_gpio_reset, 0);
+		if (rc)
+			return rc;
+
+		udelay(1200);
+	}
+	return 0;
+}
+
 int spi_nor_scan(struct spi_nor *nor)
 {
 	struct spi_nor_flash_parameter params;
@@ -4440,6 +4472,12 @@ int spi_nor_scan(struct spi_nor *nor)
 
 	nor->setup = spi_nor_default_setup;
 
+	if (CONFIG_IS_ENABLED(DM_GPIO)) {
+		ret = spi_nor_hw_reset(nor);
+		if (ret)
+			return ret;
+	}
+
 #ifdef CONFIG_SPI_FLASH_SOFT_RESET_ON_BOOT
 	/*
 	 * When the flash is handed to us in a stateful mode like 8D-8D-8D, it
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index b8b207f7b5..eb2e9c90b2 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -583,6 +583,7 @@ struct spi_nor {
 	u8			cmd_buf[SPI_NOR_MAX_CMD_SIZE];
 	enum spi_nor_cmd_ext	cmd_ext_type;
 	struct spi_nor_fixups	*fixups;
+	struct gpio_desc	*flash_gpio_reset;
 
 	int (*setup)(struct spi_nor *nor, const struct flash_info *info,
 		     const struct spi_nor_flash_parameter *params);
-- 
2.17.1