mtd: spi-nor: core: Add helpers to read/write any register

There are manufacturers that use registers indexed by address. Some of
them support "read/write any register" opcodes. Provide core methods that
can be used by all manufacturers. SPI NOR controller ops are intentionally
not supported as we intend to move all the SPI NOR controller drivers
under the SPI subsystem.

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Pratyush Yadav <p.yadav@ti.com>
Tested-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Reviewed-by: Pratyush Yadav <p.yadav@ti.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Link: https://lore.kernel.org/r/20220420103427.47867-7-tudor.ambarus@microchip.com

drivers/mtd/spi-nor/core.c

@@ -307,6 +307,52 @@ ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
 	return nor->controller_ops->write(nor, to, len, buf);
 }
 
+/**
+ * spi_nor_read_any_reg() - read any register from flash memory, nonvolatile or
+ * volatile.
+ * @nor:        pointer to 'struct spi_nor'.
+ * @op:		SPI memory operation. op->data.buf must be DMA-able.
+ * @proto:	SPI protocol to use for the register operation.
+ *
+ * Return: zero on success, -errno otherwise
+ */
+int spi_nor_read_any_reg(struct spi_nor *nor, struct spi_mem_op *op,
+			 enum spi_nor_protocol proto)
+{
+	if (!nor->spimem)
+		return -EOPNOTSUPP;
+
+	spi_nor_spimem_setup_op(nor, op, proto);
+	return spi_nor_spimem_exec_op(nor, op);
+}
+
+/**
+ * spi_nor_write_any_volatile_reg() - write any volatile register to flash
+ * memory.
+ * @nor:        pointer to 'struct spi_nor'
+ * @op:		SPI memory operation. op->data.buf must be DMA-able.
+ * @proto:	SPI protocol to use for the register operation.
+ *
+ * Writing volatile registers are instant according to some manufacturers
+ * (Cypress, Micron) and do not need any status polling.
+ *
+ * Return: zero on success, -errno otherwise
+ */
+int spi_nor_write_any_volatile_reg(struct spi_nor *nor, struct spi_mem_op *op,
+				   enum spi_nor_protocol proto)
+{
+	int ret;
+
+	if (!nor->spimem)
+		return -EOPNOTSUPP;
+
+	ret = spi_nor_write_enable(nor);
+	if (ret)
+		return ret;
+	spi_nor_spimem_setup_op(nor, op, proto);
+	return spi_nor_spimem_exec_op(nor, op);
+}
+
 /**
  * spi_nor_write_enable() - Set write enable latch with Write Enable command.
  * @nor:	pointer to 'struct spi_nor'.

drivers/mtd/spi-nor/core.h

@@ -554,6 +554,10 @@ ssize_t spi_nor_read_data(struct spi_nor *nor, loff_t from, size_t len,
 			  u8 *buf);
 ssize_t spi_nor_write_data(struct spi_nor *nor, loff_t to, size_t len,
 			   const u8 *buf);
+int spi_nor_read_any_reg(struct spi_nor *nor, struct spi_mem_op *op,
+			 enum spi_nor_protocol proto);
+int spi_nor_write_any_volatile_reg(struct spi_nor *nor, struct spi_mem_op *op,
+				   enum spi_nor_protocol proto);
 int spi_nor_erase_sector(struct spi_nor *nor, u32 addr);
 
 int spi_nor_otp_read_secr(struct spi_nor *nor, loff_t addr, size_t len, u8 *buf);