Commit 74317984 authored by Jean-Christophe PLAGNIOL-VILLARD's avatar Jean-Christophe PLAGNIOL-VILLARD Committed by Grant Likely

of_spi: add generic binding support to specify cs gpio

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: default avatarJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: devicetree-discuss@lists.ozlabs.org
Cc: spi-devel-general@lists.sourceforge.net
Signed-off-by: default avatarRichard Genoud <richard.genoud@gmail.com>
[grant.likely: fixed up type of cs count so min() can do type checking]
Signed-off-by: default avatarGrant Likely <grant.likely@secretlab.ca>
parent 15d0983f
......@@ -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>;
......
......@@ -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...
......@@ -946,6 +952,44 @@ 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)
{
u16 nb;
int i, *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()
......@@ -977,6 +1021,10 @@ 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
*/
......
......@@ -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)
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment