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 boolean variable to indicate both the GPIO CS and
the internal chip select 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.
---
drivers/spi/spi.c | 10 ++++++++--
include/linux/spi/spi.h | 1 +
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 5787b72..c042a8c 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -697,10 +697,14 @@ 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->set_cs && spi->master->gpio_ss)
+ spi->master->set_cs(spi, !enable);
+ } else if (spi->master->set_cs) {
spi->master->set_cs(spi, !enable);
+ }
}
#ifdef CONFIG_HAS_DMA
@@ -1845,6 +1849,8 @@ static int of_spi_register_master(struct spi_master
*master)
for (i = 0; i < nb; i++)
cs[i] = of_get_named_gpio(np, "cs-gpios", i);
+ master->gpio_ss = of_property_read_bool(np, "gpio-ss");
+
return 0;
}
#else
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 4b743ac..0437995 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -551,6 +551,7 @@ struct spi_master {
/* gpio chip select */
int *cs_gpios;
+ bool gpio_ss;
/* statistics */
struct spi_statistics statistics;
--
1.7.9.5
