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

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Date:   Thu, 1 Sep 2022 12:59:14 +0530
From:   Sai Krishna Potthuri <sai.krishna.potthuri@....com>
To:     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>, Sai Krishna Potthuri <sai.krishna.potthuri@....com>
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 <sai.krishna.potthuri@....com>
---
 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