[PATCH 1/2] mtd: spi-nor: add Global Block Unlock support

[Tudor.Ambarus]

From: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>

To avoid inadvertent writes during power-up, some flashes are
write-protected by default after a power-on reset cycle.
A Global Block-Protection Unlock command offers a single
command cycle that unlocks the entire memory array. This is
identical with what other nor flashes are doing by clearing
the block protection bits from the status register: disable
the write protection after a power-on reset cycle.

We can't determine this purely by manufacturer type and it's not
autodetectable by anything like SFDP, so make a new flag for it:
UNLOCK_GLOBAL_BLOCK.

Note that the Global Block Unlock command has different names
depending on the manufacturer, but always the same command value:
0x98. Macronix's MX25U12835F names it Gang Block Unlock,
Winbound's W25Q128FV names it Global Block Unlock and
Microchip's SST26VF064B names it Global Block Protection Unlock.

Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
---
 drivers/mtd/spi-nor/spi-nor.c | 47 ++++++++++++++++++++++++++++++++++++++++++-
 include/linux/mtd/spi-nor.h   |  1 +
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
index f5c1c71caf1b..08ae45fdc44a 100644
--- a/drivers/mtd/spi-nor/spi-nor.c
+++ b/drivers/mtd/spi-nor/spi-nor.c
@@ -186,7 +186,7 @@ struct flash_info {
 	u16		page_size;
 	u16		addr_width;
 
-	u16		flags;
+	u32		flags;
 #define SECT_4K			BIT(0)	/* SPINOR_OP_BE_4K works uniformly */
 #define SPI_NOR_NO_ERASE	BIT(1)	/* No erase command needed */
 #define SST_WRITE		BIT(2)	/* use SST byte programming */
@@ -215,6 +215,7 @@ struct flash_info {
 #define SPI_NOR_SKIP_SFDP	BIT(13)	/* Skip parsing of SFDP tables */
 #define USE_CLSR		BIT(14)	/* use CLSR command */
 #define SPI_NOR_OCTAL_READ	BIT(15)	/* Flash supports Octal Read */
+#define UNLOCK_GLOBAL_BLOCK	BIT(16)	/* Unlock global block protection */
 
 	/* Part specific fixup hooks. */
 	const struct spi_nor_fixups *fixups;
@@ -2025,6 +2026,41 @@ static int spi_nor_spansion_clear_sr_bp(struct spi_nor *nor)
 	return spi_nor_clear_sr_bp(nor);
 }
 
+/**
+ * spi_nor_unlock_global_block_protection() - Unlock the Global Block Protection
+ * @nor:        pointer to a 'struct spi_nor'
+ *
+ * The Global Block-Protection Unlock command offers a single command cycle
+ * that unlocks the entire memory array.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spi_nor_unlock_global_block_protection(struct spi_nor *nor)
+{
+	int ret;
+
+	write_enable(nor);
+
+	if (nor->spimem) {
+		struct spi_mem_op op =
+			SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_ULBPR, 1),
+				   SPI_MEM_OP_NO_ADDR,
+				   SPI_MEM_OP_NO_DUMMY,
+				   SPI_MEM_OP_NO_DATA);
+
+		ret = spi_mem_exec_op(nor->spimem, &op);
+	} else {
+		ret = nor->write_reg(nor, SPINOR_OP_ULBPR, NULL, 0);
+	}
+
+	if (ret < 0) {
+		dev_err(nor->dev, "error %d on ULBPR\n", ret);
+		return ret;
+	}
+
+	return spi_nor_wait_till_ready(nor);
+}
+
 /* Used when the "_ext_id" is two bytes at most */
 #define INFO(_jedec_id, _ext_id, _sector_size, _n_sectors, _flags)	\
 		.id = {							\
@@ -4506,6 +4542,15 @@ static int spi_nor_disable_block_protection(struct spi_nor *nor)
 		nor->params.disable_block_protection =
 			spi_nor_spansion_clear_sr_bp;
 
+	/*
+	 * If the flash supports the Global Block-Protection Unlock command,
+	 * use it for faster throughput: a single command cycle that unlocks
+	 * the entire memory array.
+	 */
+	if (nor->info->flags & UNLOCK_GLOBAL_BLOCK)
+		nor->params.disable_block_protection =
+			spi_nor_unlock_global_block_protection;
+
 	return nor->params.disable_block_protection(nor);
 }
 
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index a3a765c21edc..8c07b06ad0e8 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -66,6 +66,7 @@
 #define SPINOR_OP_CLFSR		0x50	/* Clear flag status register */
 #define SPINOR_OP_RDEAR		0xc8	/* Read Extended Address Register */
 #define SPINOR_OP_WREAR		0xc5	/* Write Extended Address Register */
+#define SPINOR_OP_ULBPR		0x98	/* Global Block Unlock Protection */
 
 /* 4-byte address opcodes - used on Spansion and some Macronix flashes. */
 #define SPINOR_OP_READ_4B	0x13	/* Read data bytes (low frequency) */
-- 
2.9.5