[PATCH v4 3/6] mtd: spi-nor: spansion: Add support for Read/Write Any Register

[tkuw584924 at gmail.com]

From: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>

Some of Spansion/Cypress chips support Read/Write Any Register commands.
These commands are mainly used to write volatile registers and access to
the registers in second and subsequent die for multi-die package parts.

The Read Any Register instruction (65h) is followed by register address
and dummy cycles, then the selected register byte is returned.

The Write Any Register instruction (71h) is followed by register address
and register byte to write.

Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
---
Changes in v4:
  - Fix dummy cycle calculation in spansion_read_any_reg()
  - Modify comment for spansion_write_any_reg()
  
Changes in v3:
  - Cleanup implementation

 drivers/mtd/spi-nor/spansion.c | 106 +++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)

diff --git a/drivers/mtd/spi-nor/spansion.c b/drivers/mtd/spi-nor/spansion.c
index b0c5521c1e27..52a427d0af02 100644
--- a/drivers/mtd/spi-nor/spansion.c
+++ b/drivers/mtd/spi-nor/spansion.c
@@ -19,6 +19,112 @@
 #define SPINOR_REG_CYPRESS_CFR5V_OCT_DTR_DS	0
 #define SPINOR_OP_CYPRESS_RD_FAST		0xee
 
+/**
+ * spansion_read_any_reg() - Read Any Register.
+ * @nor:	pointer to a 'struct spi_nor'
+ * @reg_addr:	register address
+ * @reg_dummy:	number of dummy cycles for register read
+ * @reg_val:	pointer to a buffer where the register value is copied into
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spansion_read_any_reg(struct spi_nor *nor, u32 reg_addr,
+				 u8 reg_dummy, u8 *reg_val)
+{
+	ssize_t ret;
+
+	if (nor->spimem) {
+		struct spi_mem_op op =
+			SPI_MEM_OP(SPI_MEM_OP_CMD(SPINOR_OP_RD_ANY_REG, 0),
+				   SPI_MEM_OP_ADDR(nor->addr_width, reg_addr, 0),
+				   SPI_MEM_OP_DUMMY(reg_dummy, 0),
+				   SPI_MEM_OP_DATA_IN(1, reg_val, 0));
+
+		spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
+
+		op.dummy.nbytes = (reg_dummy * op.dummy.buswidth) / 8;
+		if (spi_nor_protocol_is_dtr(nor->reg_proto))
+			op.dummy.nbytes *= 2;
+
+		ret = spi_mem_exec_op(nor->spimem, &op);
+	} else {
+		enum spi_nor_protocol proto = nor->read_proto;
+		u8 opcode = nor->read_opcode;
+		u8 dummy = nor->read_dummy;
+
+		nor->read_opcode = SPINOR_OP_RD_ANY_REG;
+		nor->read_dummy = reg_dummy;
+		nor->read_proto = nor->reg_proto;
+
+		ret = nor->controller_ops->read(nor, reg_addr, 1, reg_val);
+
+		nor->read_opcode = opcode;
+		nor->read_dummy = dummy;
+		nor->read_proto = proto;
+
+		if (ret == 1)
+			return ret;
+		if (ret != 1)
+			return -EIO;
+
+		ret = 0;
+	}
+
+	return ret;
+}
+
+/**
+ * spansion_write_any_reg() - Write Any Register.
+ * @nor:	pointer to a 'struct spi_nor'
+ * @reg_addr:	register address (should be a volatile register)
+ * @reg_val:	register value to be written
+ *
+ * Volatile register write will be effective immediately after the operation so
+ * this function does not poll the status.
+ *
+ * Return: 0 on success, -errno otherwise.
+ */
+static int spansion_write_any_reg(struct spi_nor *nor, u32 reg_addr, u8 reg_val)
+{
+	ssize_t 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_WR_ANY_REG, 0),
+				   SPI_MEM_OP_ADDR(nor->addr_width, reg_addr, 0),
+				   SPI_MEM_OP_NO_DUMMY,
+				   SPI_MEM_OP_DATA_OUT(1, &reg_val, 0));
+
+		spi_nor_spimem_setup_op(nor, &op, nor->reg_proto);
+
+		ret = spi_mem_exec_op(nor->spimem, &op);
+	} else {
+		enum spi_nor_protocol proto = nor->write_proto;
+		u8 opcode = nor->program_opcode;
+
+		nor->program_opcode = SPINOR_OP_WR_ANY_REG;
+		nor->write_proto = nor->reg_proto;
+
+		ret = nor->controller_ops->write(nor, reg_addr, 1, &reg_val);
+
+		nor->program_opcode = opcode;
+		nor->write_proto = proto;
+
+		if (ret < 0)
+			return ret;
+		if (ret != 1)
+			return -EIO;
+
+		ret = 0;
+	}
+
+	return ret;
+}
+
 /**
  * spi_nor_cypress_octal_dtr_enable() - Enable octal DTR on Cypress flashes.
  * @nor:		pointer to a 'struct spi_nor'
-- 
2.25.1