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From:   Michal Suchanek <msuchanek@suse.de>
To:     linux-sunxi@lists.linux.dev
Cc:     Michal Suchanek <msuchanek@suse.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Chen-Yu Tsai <wens@csie.org>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Samuel Holland <samuel@sholland.org>,
        Tudor Ambarus <tudor.ambarus@microchip.com>,
        Pratyush Yadav <p.yadav@ti.com>,
        Michael Walle <michael@walle.cc>,
        Miquel Raynal <miquel.raynal@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org
Subject: [PATCH 1/2] mtd: spi-nor: When a flash memory is missing do not report an error
Date:   Thu, 14 Jul 2022 21:19:47 +0200
Message-Id: <701967b0c418db333c66b48d225df60aa9d03ead.1657826188.git.msuchanek@suse.de>
MIME-Version: 1.0
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It is normal that devices are designed with multiple types of storage,
and only some types of storage are present.

The kernel can handle this situation gracefully for many types of
storage devices such as mmc or ata but it reports and error when spi
flash is not present.

Only print a notice that the storage device is missing when no response
to the identify command is received.

Consider reply buffers with all bits set to the same value no response.

Signed-off-by: Michal Suchanek <msuchanek@suse.de>
---
 drivers/mtd/spi-nor/core.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index 502967c76c5f..6bab540171a4 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -1652,6 +1652,24 @@ static const struct flash_info *spi_nor_match_id(struct spi_nor *nor,
 	return NULL;
 }
 
+static const bool buffer_uniform(const u8 *buffer, size_t length)
+{
+	bool all0;
+	size_t i;
+
+	for (all0 = true, i = 0; i < length; i++)
+		if (buffer[i] != 0) {
+			all0 = false;
+			break;
+		}
+	if (all0)
+		return true;
+	for (i = 0; i < length; i++)
+		if (buffer[i] != 0xff)
+			return false;
+	return true;
+}
+
 static const struct flash_info *spi_nor_detect(struct spi_nor *nor)
 {
 	const struct flash_info *info;
@@ -1666,8 +1684,11 @@ static const struct flash_info *spi_nor_detect(struct spi_nor *nor)
 
 	info = spi_nor_match_id(nor, id);
 	if (!info) {
-		dev_err(nor->dev, "unrecognized JEDEC id bytes: %*ph\n",
-			SPI_NOR_MAX_ID_LEN, id);
+		if (buffer_uniform(id, SPI_NOR_MAX_ID_LEN))
+			dev_info(nor->dev, "No flash memory detected.\n");
+		else
+			dev_err(nor->dev, "unrecognized JEDEC id bytes: %*ph\n",
+				SPI_NOR_MAX_ID_LEN, id);
 		return ERR_PTR(-ENODEV);
 	}
 	return info;
-- 
2.35.3