[PATCH] mtd: spi-nor: add support for Fudan Microelectronics FM25Q256

[Cole Leavitt <cole@unwrap.rs>]

Add support for the Fudan Microelectronics FM25Q256 (JEDEC ID f7 f0 30),
a 256Mbit (32MB) SPI NOR flash chip. This chip is found on Lenovo
ThinkPad P16 Gen 3 (Arrow Lake-S) platforms as the SPI flash backing
the UEFI firmware.

The chip supports 4K sector erase, dual read, and quad read modes.

Without this patch, the kernel's spi-nor driver reports:
  spi-nor spi0.0: unrecognized JEDEC id bytes: f7 f0 30
and refuses to create an MTD device, preventing userspace tools from
accessing the flash.

Signed-off-by: Cole Leavitt <cole@unwrap.rs>
---
 drivers/mtd/spi-nor/Makefile |  1 +
 drivers/mtd/spi-nor/core.c   |  1 +
 drivers/mtd/spi-nor/core.h   |  1 +
 drivers/mtd/spi-nor/fudan.c  | 25 +++++++++++++++++++++++++
 4 files changed, 28 insertions(+)
 create mode 100644 drivers/mtd/spi-nor/fudan.c

diff --git a/drivers/mtd/spi-nor/Makefile b/drivers/mtd/spi-nor/Makefile
index 5dd9c35f6b6f..2c8b9b3e08bb 100644
--- a/drivers/mtd/spi-nor/Makefile
+++ b/drivers/mtd/spi-nor/Makefile
@@ -5,6 +5,7 @@ spi-nor-objs			+= atmel.o
 spi-nor-objs			+= eon.o
 spi-nor-objs			+= esmt.o
 spi-nor-objs			+= everspin.o
+spi-nor-objs			+= fudan.o
 spi-nor-objs			+= gigadevice.o
 spi-nor-objs			+= intel.o
 spi-nor-objs			+= issi.o
diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
index d3f8a78efd3b..395ff5c39883 100644
--- a/drivers/mtd/spi-nor/core.c
+++ b/drivers/mtd/spi-nor/core.c
@@ -1944,6 +1944,7 @@ static const struct spi_nor_manufacturer *manufacturers[] = {
 	&spi_nor_eon,
 	&spi_nor_esmt,
 	&spi_nor_everspin,
+	&spi_nor_fudan,
 	&spi_nor_gigadevice,
 	&spi_nor_intel,
 	&spi_nor_issi,
diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
index 16b382d4f04f..be63273677c8 100644
--- a/drivers/mtd/spi-nor/core.h
+++ b/drivers/mtd/spi-nor/core.h
@@ -594,6 +594,7 @@ extern const struct spi_nor_manufacturer spi_nor_atmel;
 extern const struct spi_nor_manufacturer spi_nor_eon;
 extern const struct spi_nor_manufacturer spi_nor_esmt;
 extern const struct spi_nor_manufacturer spi_nor_everspin;
+extern const struct spi_nor_manufacturer spi_nor_fudan;
 extern const struct spi_nor_manufacturer spi_nor_gigadevice;
 extern const struct spi_nor_manufacturer spi_nor_intel;
 extern const struct spi_nor_manufacturer spi_nor_issi;
diff --git a/drivers/mtd/spi-nor/fudan.c b/drivers/mtd/spi-nor/fudan.c
new file mode 100644
index 000000000000..e9a4d3ed3cd0
--- /dev/null
+++ b/drivers/mtd/spi-nor/fudan.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Fudan Microelectronics SPI NOR flash support.
+ *
+ * JEDEC manufacturer ID 0xf7.
+ */
+
+#include <linux/mtd/spi-nor.h>
+
+#include "core.h"
+
+static const struct flash_info fudan_nor_parts[] = {
+	{
+		.id = SNOR_ID(0xf7, 0xf0, 0x30),
+		.name = "fm25q256",
+		.size = SZ_32M,
+		.no_sfdp_flags = SECT_4K | SPI_NOR_DUAL_READ | SPI_NOR_QUAD_READ,
+	},
+};
+
+const struct spi_nor_manufacturer spi_nor_fudan = {
+	.name = "fudan",
+	.parts = fudan_nor_parts,
+	.nparts = ARRAY_SIZE(fudan_nor_parts),
+};

base-commit: 2687c848e57820651b9f69d30c4710f4219f7dbf
-- 
2.52.0

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