This will allow to use gpio for chip select with no modification in the
driver binding
When use the cs-gpios, the gpio number will be passed via the cs_gpio field
and the number of chip select will automatically increased with max(hw cs, gpio
cs).
So if for example the controller has 2 CS lines, and the cs-gpios
property looks like this:
cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;
Then it should be configured so that num_chipselect = 4 with the
following mapping:
cs0 : &gpio1 0 0
cs1 : native
cs2 : &gpio1 1 0
cs3 : &gpio1 2 0
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagn...@jcrosoft.com>
Cc: devicetree-disc...@lists.ozlabs.org
Cc: spi-devel-general@lists.sourceforge.net
Signed-off-by: Richard Genoud <richard.gen...@gmail.com>
---
v2:
update to allow to overwrite hw gpio via cs-gpio
as sugested by Grant
Best Regards,
J.
Documentation/devicetree/bindings/spi/spi-bus.txt | 20 ++++++++
drivers/spi/spi.c | 54 +++++++++++++++++++--
include/linux/spi/spi.h | 3 ++
3 files changed, 74 insertions(+), 3 deletions(-)
diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt
b/Documentation/devicetree/bindings/spi/spi-bus.txt
index d2c33d0..77a8b0d 100644
--- a/Documentation/devicetree/bindings/spi/spi-bus.txt
+++ b/Documentation/devicetree/bindings/spi/spi-bus.txt
@@ -12,6 +12,7 @@ The SPI master node requires the following properties:
- #size-cells - should be zero.
- compatible - name of SPI bus controller following generic names
recommended practice.
+- cs-gpios - (optional) gpios chip select.
No other properties are required in the SPI bus node. It is assumed
that a driver for an SPI bus device will understand that it is an SPI bus.
However, the binding does not attempt to define the specific method for
@@ -24,6 +25,22 @@ support describing the chip select layout.
Optional property:
- num-cs : total number of chipselects
+If cs-gpios is used the number of chip select will automatically increased
+with max(cs-gpios > hw cs)
+
+So if for example the controller has 2 CS lines, and the cs-gpios
+property looks like this:
+
+cs-gpios = <&gpio1 0 0> <0> <&gpio1 1 0> <&gpio1 2 0>;
+
+Then it should be configured so that num_chipselect = 4 with the
+following mapping:
+
+cs0 : &gpio1 0 0
+cs1 : native
+cs2 : &gpio1 1 0
+cs3 : &gpio1 2 0
+
SPI slave nodes must be children of the SPI master node and can
contain the following properties.
- reg - (required) chip select address of device.
@@ -37,6 +54,9 @@ contain the following properties.
- spi-cs-high - (optional) Empty property indicating device requires
chip select active high
+If a gpio chipselect is used for the SPI slave the gpio number will be passed
+via the cs_gpio
+
SPI example for an MPC5200 SPI bus:
spi@f00 {
#address-cells = <1>;
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index fc0da39..efb635f 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -30,6 +30,7 @@
#include <linux/slab.h>
#include <linux/mod_devicetable.h>
#include <linux/spi/spi.h>
+#include <linux/of_gpio.h>
#include <linux/pm_runtime.h>
#include <linux/export.h>
#include <linux/sched.h>
@@ -327,6 +328,7 @@ struct spi_device *spi_alloc_device(struct spi_master
*master)
spi->dev.parent = &master->dev;
spi->dev.bus = &spi_bus_type;
spi->dev.release = spidev_release;
+ spi->cs_gpio = -EINVAL;
device_initialize(&spi->dev);
return spi;
}
@@ -344,15 +346,16 @@ EXPORT_SYMBOL_GPL(spi_alloc_device);
int spi_add_device(struct spi_device *spi)
{
static DEFINE_MUTEX(spi_add_lock);
- struct device *dev = spi->master->dev.parent;
+ struct spi_master *master = spi->master;
+ struct device *dev = master->dev.parent;
struct device *d;
int status;
/* Chipselects are numbered 0..max; validate. */
- if (spi->chip_select >= spi->master->num_chipselect) {
+ if (spi->chip_select >= master->num_chipselect) {
dev_err(dev, "cs%d >= max %d\n",
spi->chip_select,
- spi->master->num_chipselect);
+ master->num_chipselect);
return -EINVAL;
}
@@ -376,6 +379,9 @@ int spi_add_device(struct spi_device *spi)
goto done;
}
+ if (master->cs_gpios)
+ spi->cs_gpio = master->cs_gpios[spi->chip_select];
+
/* Drivers may modify this initial i/o setup, but will
* normally rely on the device being setup. Devices
* using SPI_CS_HIGH can't coexist well otherwise...
@@ -949,6 +955,44 @@ struct spi_master *spi_alloc_master(struct device *dev,
unsigned size)
}
EXPORT_SYMBOL_GPL(spi_alloc_master);
+#ifdef CONFIG_OF
+static int of_spi_register_master(struct spi_master *master)
+{
+ int nb, i;
+ int *cs;
+ struct device_node *np = master->dev.of_node;
+
+ if (!np)
+ return 0;
+
+ nb = of_gpio_named_count(np, "cs-gpios");
+ master->num_chipselect = max(nb, master->num_chipselect);
+
+ if (nb < 1)
+ return 0;
+
+ cs = devm_kzalloc(&master->dev,
+ sizeof(int) * master->num_chipselect,
+ GFP_KERNEL);
+ master->cs_gpios = cs;
+
+ if (!master->cs_gpios)
+ return -ENOMEM;
+
+ memset(cs, -EINVAL, master->num_chipselect);
+
+ for (i = 0; i < nb; i++)
+ cs[i] = of_get_named_gpio(np, "cs-gpios", i);
+
+ return 0;
+}
+#else
+static int of_spi_register_master(struct spi_master *master)
+{
+ return 0;
+}
+#endif
+
/**
* spi_register_master - register SPI master controller
* @master: initialized master, originally from spi_alloc_master()
@@ -980,6 +1024,10 @@ int spi_register_master(struct spi_master *master)
if (!dev)
return -ENODEV;
+ status = of_spi_register_master(master);
+ if (status)
+ return status;
+
/* even if it's just one always-selected device, there must
* be at least one chipselect
*/
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index fa702ae..f629189 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -90,6 +90,7 @@ struct spi_device {
void *controller_state;
void *controller_data;
char modalias[SPI_NAME_SIZE];
+ int cs_gpio; /* chip select gpio */
/*
* likely need more hooks for more protocol options affecting how
@@ -362,6 +363,8 @@ struct spi_master {
int (*transfer_one_message)(struct spi_master *master,
struct spi_message *mesg);
int (*unprepare_transfer_hardware)(struct spi_master *master);
+ /* gpio chip select */
+ int *cs_gpios;
};
static inline void *spi_master_get_devdata(struct spi_master *master)
--
1.7.10.4
------------------------------------------------------------------------------
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