[PATCH] mtd: spinand: add support for HeYangTek HYF1GQ4UDACAE

[Aleksei Sviridkin <f@lex.la>]

The HeYangTek HYF1GQ4UDACAE is a 1 Gbit (128 MiB) SLC SPI-NAND with
2048 + 64 byte pages and on-die 4-bit / 512-byte ECC; its JEDEC
manufacturer ID is 0xc9. The die is GD5F1GQ4-compatible, so the OOB
layout is taken from the in-tree gd5fxgq4xa. The die exposes only a
coarse 2-bit ECC status with no fine-grained bitflip-count register, so
the status is decoded into a representative number of corrected bitflips.

It is found, among others, on some Keenetic KN-3411 (Buddy 6) units.

Datasheet:
https://www.heyangtek.cn/previewfile.jsp?file=ABUIABA9GAAgwsvRnwYo-eDpsgc

Signed-off-by: Aleksei Sviridkin <f@lex.la>
---
This revives Maxim Anisimov's 2024 submission [1], which stalled on the
review feedback. Changes since then:

 - The OOB layout no longer leaves undefined bytes: it is taken verbatim
   from the in-tree gd5fxgq4xa, which the die is compatible with (BBM in
   byte 0, ECC parity in bytes 8..15 of each 16-byte section, the rest
   exposed as free).
 - The ECC status decoding is documented and uses '/' instead of a
   shift. The die exposes only the coarse 2-bit status with no register
   for the exact bitflip count, so the below-threshold code reports
   strength/2 and the refresh-recommended code reports the full strength.
 - The datasheet link is added to the commit message.

Tested on a Keenetic KN-3411 (Buddy 6): the chip is detected and a UBIFS
rootfs mounts and runs on it. nandbiterrs is not applicable here -- this
is an on-die-ECC part with NOP=1, so the in-place raw page reprogram that
nandbiterrs relies on corrupts the page independently of this driver.

[1] https://lore.kernel.org/linux-mtd/20240624061246.5292-1-maxim.anisimov.ua@gmail.com/

 drivers/mtd/nand/spi/Makefile    |   2 +-
 drivers/mtd/nand/spi/core.c      |   1 +
 drivers/mtd/nand/spi/heyangtek.c | 132 +++++++++++++++++++++++++++++++
 include/linux/mtd/spinand.h      |   1 +
 4 files changed, 135 insertions(+), 1 deletion(-)
 create mode 100644 drivers/mtd/nand/spi/heyangtek.c

diff --git a/drivers/mtd/nand/spi/Makefile b/drivers/mtd/nand/spi/Makefile
index a47bd22cd..b5ccb4486 100644
--- a/drivers/mtd/nand/spi/Makefile
+++ b/drivers/mtd/nand/spi/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
 spinand-objs := core.o otp.o
-spinand-objs += alliancememory.o ato.o dosilicon.o esmt.o fmsh.o foresee.o gigadevice.o
+spinand-objs += alliancememory.o ato.o dosilicon.o esmt.o fmsh.o foresee.o gigadevice.o heyangtek.o
 spinand-objs += macronix.o micron.o paragon.o skyhigh.o toshiba.o winbond.o xtx.o
 obj-$(CONFIG_MTD_SPI_NAND) += spinand.o
diff --git a/drivers/mtd/nand/spi/core.c b/drivers/mtd/nand/spi/core.c
index 0b076790b..0cdd4a62e 100644
--- a/drivers/mtd/nand/spi/core.c
+++ b/drivers/mtd/nand/spi/core.c
@@ -1336,6 +1336,7 @@ static const struct spinand_manufacturer *spinand_manufacturers[] = {
 	&fmsh_spinand_manufacturer,
 	&foresee_spinand_manufacturer,
 	&gigadevice_spinand_manufacturer,
+	&heyangtek_spinand_manufacturer,
 	&macronix_spinand_manufacturer,
 	&micron_spinand_manufacturer,
 	&paragon_spinand_manufacturer,
diff --git a/drivers/mtd/nand/spi/heyangtek.c b/drivers/mtd/nand/spi/heyangtek.c
new file mode 100644
index 000000000..7fc50fd3d
--- /dev/null
+++ b/drivers/mtd/nand/spi/heyangtek.c
@@ -0,0 +1,132 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Authors:
+ *	Andrey Zolotarev <andrey.zolotarev@keenetic.com> - the main driver logic
+ *	Aleksei Sviridkin <f@lex.la> - adaptation to the mainline Linux kernel
+ *
+ * Based on:
+ *	https://github.com/keenetic/kernel-49/commit/bacade569fb12bc0ad31ba09bca9b890118fbca7
+ */
+
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/mtd/spinand.h>
+
+#define SPINAND_MFR_HEYANGTEK			0xc9
+
+#define HYF1GQ4_STATUS_ECC_LIMIT_BITFLIPS	(3 << 4)
+
+static SPINAND_OP_VARIANTS(read_cache_variants,
+		SPINAND_PAGE_READ_FROM_CACHE_1S_4S_4S_OP(0, 1, NULL, 0, 0),
+		SPINAND_PAGE_READ_FROM_CACHE_1S_1S_4S_OP(0, 1, NULL, 0, 0),
+		SPINAND_PAGE_READ_FROM_CACHE_1S_2S_2S_OP(0, 1, NULL, 0, 0),
+		SPINAND_PAGE_READ_FROM_CACHE_1S_1S_2S_OP(0, 1, NULL, 0, 0),
+		SPINAND_PAGE_READ_FROM_CACHE_FAST_1S_1S_1S_OP(0, 1, NULL, 0, 0),
+		SPINAND_PAGE_READ_FROM_CACHE_1S_1S_1S_OP(0, 1, NULL, 0, 0));
+
+static SPINAND_OP_VARIANTS(write_cache_variants,
+		SPINAND_PROG_LOAD_1S_1S_4S_OP(true, 0, NULL, 0),
+		SPINAND_PROG_LOAD_1S_1S_1S_OP(true, 0, NULL, 0));
+
+static SPINAND_OP_VARIANTS(update_cache_variants,
+		SPINAND_PROG_LOAD_1S_1S_4S_OP(false, 0, NULL, 0),
+		SPINAND_PROG_LOAD_1S_1S_1S_OP(false, 0, NULL, 0));
+
+/*
+ * HYF1GQ4UDACAE is a GD5F1GQ4-compatible die, so the OOB layout is taken
+ * from gd5fxgq4xa: the on-die ECC parity occupies bytes 8..15 of each
+ * 16-byte section, the bad block marker sits in byte 0 and the remaining
+ * bytes are exposed as free.
+ */
+static int hyf1gq4_ooblayout_ecc(struct mtd_info *mtd, int section,
+				 struct mtd_oob_region *region)
+{
+	if (section > 3)
+		return -ERANGE;
+
+	region->offset = (16 * section) + 8;
+	region->length = 8;
+
+	return 0;
+}
+
+static int hyf1gq4_ooblayout_free(struct mtd_info *mtd, int section,
+				  struct mtd_oob_region *region)
+{
+	if (section > 3)
+		return -ERANGE;
+
+	if (section) {
+		region->offset = 16 * section;
+		region->length = 8;
+	} else {
+		/* section 0 has one byte reserved for the bad block marker */
+		region->offset = 1;
+		region->length = 7;
+	}
+
+	return 0;
+}
+
+static const struct mtd_ooblayout_ops hyf1gq4_ooblayout = {
+	.ecc = hyf1gq4_ooblayout_ecc,
+	.free = hyf1gq4_ooblayout_free,
+};
+
+static int hyf1gq4_ecc_get_status(struct spinand_device *spinand, u8 status)
+{
+	struct nand_device *nand = spinand_to_nand(spinand);
+
+	switch (status & STATUS_ECC_MASK) {
+	case STATUS_ECC_NO_BITFLIPS:
+		return 0;
+
+	case STATUS_ECC_UNCOR_ERROR:
+		return -EBADMSG;
+
+	case STATUS_ECC_HAS_BITFLIPS:
+		/*
+		 * The die exposes only a coarse 2-bit ECC status and has no
+		 * register for the exact bitflip count. This code means
+		 * "corrected, below the refresh threshold", so report half of
+		 * the ECC strength as a representative value.
+		 */
+		return nanddev_get_ecc_conf(nand)->strength / 2;
+
+	case HYF1GQ4_STATUS_ECC_LIMIT_BITFLIPS:
+		/*
+		 * "Corrected, refresh recommended": report the full ECC
+		 * strength so the upper layers relocate the data.
+		 */
+		return nanddev_get_ecc_conf(nand)->strength;
+
+	default:
+		break;
+	}
+
+	return -EINVAL;
+}
+
+static const struct spinand_info heyangtek_spinand_table[] = {
+	SPINAND_INFO("HYF1GQ4UDACAE",
+		     SPINAND_ID(SPINAND_READID_METHOD_OPCODE_ADDR, 0x21),
+		     NAND_MEMORG(1, 2048, 64, 64, 1024, 20, 1, 1, 1),
+		     NAND_ECCREQ(4, 512),
+		     SPINAND_INFO_OP_VARIANTS(&read_cache_variants,
+					      &write_cache_variants,
+					      &update_cache_variants),
+		     SPINAND_HAS_QE_BIT,
+		     SPINAND_ECCINFO(&hyf1gq4_ooblayout,
+				     hyf1gq4_ecc_get_status)),
+};
+
+static const struct spinand_manufacturer_ops heyangtek_spinand_manuf_ops = {
+};
+
+const struct spinand_manufacturer heyangtek_spinand_manufacturer = {
+	.id = SPINAND_MFR_HEYANGTEK,
+	.name = "HeYangTek",
+	.chips = heyangtek_spinand_table,
+	.nchips = ARRAY_SIZE(heyangtek_spinand_table),
+	.ops = &heyangtek_spinand_manuf_ops,
+};
diff --git a/include/linux/mtd/spinand.h b/include/linux/mtd/spinand.h
index 782984ba3..48357e6ff 100644
--- a/include/linux/mtd/spinand.h
+++ b/include/linux/mtd/spinand.h
@@ -437,6 +437,7 @@ extern const struct spinand_manufacturer esmt_c8_spinand_manufacturer;
 extern const struct spinand_manufacturer fmsh_spinand_manufacturer;
 extern const struct spinand_manufacturer foresee_spinand_manufacturer;
 extern const struct spinand_manufacturer gigadevice_spinand_manufacturer;
+extern const struct spinand_manufacturer heyangtek_spinand_manufacturer;
 extern const struct spinand_manufacturer macronix_spinand_manufacturer;
 extern const struct spinand_manufacturer micron_spinand_manufacturer;
 extern const struct spinand_manufacturer paragon_spinand_manufacturer;
-- 
2.39.5


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