linux-kernel - [RFC PATCH 2/8] mtd: rawnand: ams-delta: Write protect device during probe

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Date:   Thu, 19 Jul 2018 01:57:04 +0200
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Tony Lindgren <tony@...mide.com>,
        Aaro Koskinen <aaro.koskinen@....fi>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-omap@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Artem Bityutskiy <artem.bityutskiy@...ux.intel.com>,
        Janusz Krzysztofik <jmkrzyszt@...il.com>
Subject: [RFC PATCH 2/8] mtd: rawnand: ams-delta: Write protect device during probe

Initialize NWP GPIO pin low to protect the device from hazard during
probe.  Release write protection as soon as the device is under
control.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>
---
 drivers/mtd/nand/raw/ams-delta.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/raw/ams-delta.c b/drivers/mtd/nand/raw/ams-delta.c
index 48233d638d2a..6ac38e9cfa1a 100644
--- a/drivers/mtd/nand/raw/ams-delta.c
+++ b/drivers/mtd/nand/raw/ams-delta.c
@@ -219,8 +219,8 @@ static int ams_delta_init(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, priv);
 
-	/* Set chip enabled, but  */
-	priv->gpiod_nwp = devm_gpiod_get(&pdev->dev, "nwp", GPIOD_OUT_HIGH);
+	/* Set chip enabled but write protected */
+	priv->gpiod_nwp = devm_gpiod_get(&pdev->dev, "nwp", GPIOD_OUT_LOW);
 	if (IS_ERR(priv->gpiod_nwp)) {
 		err = PTR_ERR(priv->gpiod_nwp);
 		dev_err(&pdev->dev, "NWP GPIO request failed (%d)\n", err);
@@ -267,6 +267,9 @@ static int ams_delta_init(struct platform_device *pdev)
 	if (err)
 		goto out_mtd;
 
+	/* As soon as the device is found, release write protection */
+	gpiod_set_value(priv->gpiod_nwp, 1);
+
 	/* Register the partitions */
 	mtd_device_register(mtd, partition_info, ARRAY_SIZE(partition_info));
 
@@ -288,6 +291,9 @@ static int ams_delta_cleanup(struct platform_device *pdev)
 	struct mtd_info *mtd = nand_to_mtd(&priv->nand_chip);
 	void __iomem *io_base = priv->io_base;
 
+	/* Apply write protection */
+	gpiod_set_value(priv->gpiod_nwp, 0);
+
 	/* Release resources, unregister device */
 	nand_release(mtd);
 
-- 
2.16.4