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

[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 <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);
+
+	return 0;
+}
+
 int spi_nor_scan(struct spi_nor *nor, const char *name,
 		 const struct spi_nor_hwcaps *hwcaps)
 {
+	struct device_node *np = spi_nor_get_flash_node(nor);
 	const struct flash_info *info;
 	struct device *dev = nor->dev;
 	struct mtd_info *mtd = &nor->mtd;
@@ -2965,6 +2999,14 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
 	if (!nor->bouncebuf)
 		return -ENOMEM;
 
+	if (of_property_read_bool(np, "broken-flash-reset")) {
+		nor->flags |= SNOR_F_BROKEN_RESET;
+	} else {
+		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