From: Thor Thayer <ttha...@opensource.altera.com>
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 <ttha...@opensource.altera.com>
---
v2 Move changes to SPI framework based on maintainer comments
Add a new SPI master boolean variable.
v3 Change boolean variable to master->flags based on comments
---
drivers/spi/spi.c | 9 +++++++--
include/linux/spi/spi.h | 1 +
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 5787b72..cbe15ab 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -697,10 +697,15 @@ static void spi_set_cs(struct spi_device *spi, bool
enable)
if (spi->mode & SPI_CS_HIGH)
enable = !enable;
- if (gpio_is_valid(spi->cs_gpio))
+ if (gpio_is_valid(spi->cs_gpio)) {
gpio_set_value(spi->cs_gpio, !enable);
- else if (spi->master->set_cs)
+ /* Some SPI masters need both GPIO CS & slave_select */
+ if ((spi->master->flags & SPI_MASTER_GPIO_SS) &&
+ spi->master->set_cs)
+ spi->master->set_cs(spi, !enable);
+ } else if (spi->master->set_cs) {
spi->master->set_cs(spi, !enable);
+ }
}
#ifdef CONFIG_HAS_DMA
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
--
1.7.9.5
