spi: Add Flag to Enable Slave Select with GPIO Chip Select.
Some SPI masters require slave selection before the transfer
can begin [1]. The SPI framework currently selects the chip using
either 1) the internal CS mechanism or 2) the GPIO CS, but not both.
This patch adds a new master->flags define to indicate both the GPIO
CS and the internal chip select mechanism should be used.
Tested On:
Altera CycloneV development kit
Compile tested for build errors on x86_64 (allyesconfigs)
[1] DesignWare dw_apb_ssi Databook, Version 3.20a (page 39)
Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 4b743ac..75c6bd0 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -442,6 +442,7 @@ struct spi_master {
#define SPI_MASTER_NO_TX BIT(2) /* can't do buffer write */
#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */
#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
+#define SPI_MASTER_GPIO_SS BIT(5) /* GPIO CS must select slave */
/*
* on some hardware transfer / message size may be constrained