This patch enables data stripe feature in spi core. This feature is
required to support dual parallel mode of ZynqMP GQSPI controller.
To achieve the same an API SPI_MASTER_DATA_STRIPE is added.
With data stripe enabled,
- even bytes i.e. 0, 2, 4,... are transmitted on lower data bus
- odd bytes i.e. 1, 3, 5,.. are transmitted on upper data bus.
To support data stripe; need to assert both chip selects once.
This is achieved through API SPI_MASTER_BOTH_CS.
Signed-off-by: Naga Sureshkumar Relli <nagas...@xilinx.com>
---
Changes for v4:
- No changes, sending the previous one as is
Change for v3:
- Updated comments for newly added APIs
- Changed patch description for ease of understanding
Changes for v2:
- Added error handling condition for newly added features
---
drivers/spi/spi.c | 8 ++++++++
include/linux/spi/spi.h | 11 +++++++++++
2 files changed, 19 insertions(+)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 5787b72..01980af 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2538,6 +2538,14 @@ static int __spi_validate(struct spi_device *spi, struct
spi_message *message)
if (list_empty(&message->transfers))
return -EINVAL;
+ /*
+ * Data stripe option is selected if and only if when
+ * two chips are enabled
+ */
+ if ((master->flags & SPI_MASTER_DATA_STRIPE)
+ && !(master->flags & SPI_MASTER_BOTH_CS))
+ return -EINVAL;
+
/* Half-duplex links include original MicroWire, and ones with
* only one data pin like SPI_3WIRE (switches direction) or where
* either MOSI or MISO is missing. They can also be caused by
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 4b743ac..94a5e6a 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -443,6 +443,17 @@ struct spi_master {
#define SPI_MASTER_MUST_RX BIT(3) /* requires rx */
#define SPI_MASTER_MUST_TX BIT(4) /* requires tx */
+ /* Controller may support data stripe feature when more than one
+ * chips are present.
+ * Setting data stripe will send data in following manner:
+ * -> even bytes i.e. 0, 2, 4,... are transmitted on lower data bus
+ * -> odd bytes i.e. 1, 3, 5,.. are transmitted on upper data bus
+ */
+#define SPI_MASTER_DATA_STRIPE BIT(7) /* support data stripe */
+ /* Controller may support asserting more than one chip select at once.
+ * This flag will enable that feature.
+ */
+#define SPI_MASTER_BOTH_CS BIT(8) /* assert both chip selects */
/*
* on some hardware transfer / message size may be constrained
* the limit may depend on device transfer settings
--
2.10.2
