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

Documentation/devicetree/bindings/spi/spi-bus.txt

+20 −0
Original line number Diff line number Diff line
@@ -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>;

drivers/spi/spi.c

+51 −3
Original line number Diff line number Diff line
@@ -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

	 */

include/linux/spi/spi.h

+3 −0
Original line number Diff line number Diff line
@@ -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)