spi: spi-mem: Add SPI_MEM_NO_DATA to the spi_mem_data_dir enum

Commit: 0ebb261a0b2d ("spi: spi-mem: Add SPI_MEM_NO_DATA to the spi_mem_data_dir enum")
in linux.

When defining spi_mem_op templates we don't necessarily know the size
that will be passed when the template is actually used, and basing the
supports_op() check on op->data.nbytes to know whether there will be
data transferred for a specific operation is not possible.

Add SPI_MEM_NO_DATA to the spi_mem_data_dir enum so that we can base
our checks on op->data.dir instead of op->data.nbytes.

This also fixes a bug identified with the atmel-quaspi driver.
The spi-nor core, when erasing sectors, fills the spi_mem_op template
using SPI_MEM_OP_NO_DATA, which initializes all the data members with
value zero. This is wrong because data.dir is treated as SPI_MEM_DATA_IN,
which translates in our driver to read accesses for erases (RICR), while
the controller expects write accesses (WICR).

Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>

drivers/spi/spi-mem.c

@@ -153,7 +153,7 @@ bool spi_mem_default_supports_op(struct spi_slave *slave,
 	    spi_check_buswidth_req(slave, op->dummy.buswidth, true))
 		return false;
 
-	if (op->data.nbytes &&
+	if (op->data.dir != SPI_MEM_NO_DATA &&
 	    spi_check_buswidth_req(slave, op->data.buswidth,
 				   op->data.dir == SPI_MEM_DATA_OUT))
 		return false;

include/spi-mem.h

@@ -60,10 +60,12 @@
 /**
  * enum spi_mem_data_dir - describes the direction of a SPI memory data
  *			   transfer from the controller perspective
+ * @SPI_MEM_NO_DATA: no data transferred
  * @SPI_MEM_DATA_IN: data coming from the SPI memory
  * @SPI_MEM_DATA_OUT: data sent the SPI memory
  */
 enum spi_mem_data_dir {
+	SPI_MEM_NO_DATA,
 	SPI_MEM_DATA_IN,
 	SPI_MEM_DATA_OUT,
 };