mtd: spi-nor: Add Global Block Unlock command

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, Winbond's
W25Q128FV names it Global Block Unlock and Microchip's
SST26VF064B names it Global Block Protection Unlock.

Used in the Individual Block Protection mode, which is mutually
exclusive with the Block Protection mode (BP0-3).
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20210121110546.382633-1-tudor.ambarus@microchip.com

drivers/mtd/spi-nor/core.c

@@ -853,6 +853,43 @@ int spi_nor_wait_till_ready(struct spi_nor *nor)
 						    DEFAULT_READY_WAIT_JIFFIES);
 }
 
+/**
+ * spi_nor_global_block_unlock() - Unlock Global Block Protection.
+ * @nor:	pointer to 'struct spi_nor'.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+int spi_nor_global_block_unlock(struct spi_nor *nor)
+{
+	int ret;
+
+	ret = spi_nor_write_enable(nor);
+	if (ret)
+		return ret;
+
+	if (nor->spimem) {
+		struct spi_mem_op op =
+			SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_GBULK, 0),
+				   SPI_MEM_OP_NO_ADDR,
+				   SPI_MEM_OP_NO_DUMMY,
+				   SPI_MEM_OP_NO_DATA);
+
+		spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
+
+		ret = spi_mem_exec_op(nor->spimem, &op);
+	} else {
+		ret = spi_nor_controller_ops_write_reg(nor, SPINOR_OP_GBULK,
+						       NULL, 0);
+	}
+
+	if (ret) {
+		dev_dbg(nor->dev, "error %d on Global Block Unlock\n", ret);
+		return ret;
+	}
+
+	return spi_nor_wait_till_ready(nor);
+}
+
 /**
  * spi_nor_write_sr() - Write the Status Register.
  * @nor:	pointer to 'struct spi_nor'.

drivers/mtd/spi-nor/core.h

@@ -434,6 +434,7 @@ int spi_nor_write_disable(struct spi_nor *nor);
 int spi_nor_set_4byte_addr_mode(struct spi_nor *nor, bool enable);
 int spi_nor_write_ear(struct spi_nor *nor, u8 ear);
 int spi_nor_wait_till_ready(struct spi_nor *nor);
+int spi_nor_global_block_unlock(struct spi_nor *nor);
 int spi_nor_lock_and_prep(struct spi_nor *nor);
 void spi_nor_unlock_and_unprep(struct spi_nor *nor);
 int spi_nor_sr1_bit6_quad_enable(struct spi_nor *nor);

include/linux/mtd/spi-nor.h

@@ -53,6 +53,7 @@
 #define SPINOR_OP_WREAR		0xc5	/* Write Extended Address Register */
 #define SPINOR_OP_SRSTEN	0x66	/* Software Reset Enable */
 #define SPINOR_OP_SRST		0x99	/* Software Reset */
+#define SPINOR_OP_GBULK		0x98    /* Global Block Unlock */
 
 /* 4-byte address opcodes - used on Spansion and some Macronix flashes. */
 #define SPINOR_OP_READ_4B	0x13	/* Read data bytes (low frequency) */