On Fri, Oct 24, 2008 at 10:08:59PM +0200, Wolfgang Ocker wrote:
> SPI slave devices require the specification of a chip select address.
> This patch allows that specification using the gpios property. The reg
> property remains supported.
>
> Signed-off-by: Wolfgang Ocker <[EMAIL PROTECTED]>
> ---
>
> --- linux-2.6.27.3/drivers/of/of_spi.c.of_spi_gpio 2008-10-22
> 23:38:01.000000000 +0200
> +++ linux-2.6.27.3/drivers/of/of_spi.c.of_spi_cshigh 2008-10-24
> 21:36:39.000000000 +0200
[...]
> --- linux-2.6.27.3/Documentation/powerpc/booting-without-of.txt.of_spi_gpio
> 2008-10-22 23:38:01.000000000 +0200
> +++ linux-2.6.27.3/Documentation/powerpc/booting-without-of.txt.of_spi_cshigh
> 2008-10-24 21:57:16.000000000 +0200
> @@ -1909,7 +1909,9 @@ platforms are moved over to use the flat
>
> SPI slave nodes must be children of the SPI master node and can
> contain the following properties.
> - - reg - (required) chip select address of device.
> + - reg - chip select address of device.
> + - gpios - chip select address of device (alternatively).
> + one of reg and gpios is required.
> - compatible - (required) name of SPI device following generic names
> recommended practice
> - spi-max-frequency - (required) Maximum SPI clocking speed of device in
> Hz
> @@ -1936,7 +1938,7 @@ platforms are moved over to use the flat
> [EMAIL PROTECTED] {
> compatible = "ti,tlv320aic26";
> spi-max-frequency = <100000>;
> - reg = <1>;
> + gpios = <&GPIO1 3>;
> };
> };
Close, but no cigar. Sorry. ;-) The bindings are fine as is, you don't
need to change them.
The scheme should look like this:
spi-controller {
#address-cells = <1>;
#size-cells = <0>;
/* two GPIOs, representing two chip selects: 0 and 1 */
gpios = <&pio 5 0 &pio 16 0>;
[EMAIL PROTECTED] {
reg = <0>;
};
[EMAIL PROTECTED] {
reg = <1>;
};
}
Notice that "gpios" is spi-controller's property, not spi devices'.
It is truly as hardware works, SPI controllers consists of two units:
I/O, and chip-select machine. Most spi controllers don't have
dedicated chip-select machines, so they use GPIOs.
The spi controller driver should request all the specified gpios,
and then work with chip select numbers. Something like this:
struct spi_controller {
int *gpios;
unsigned int num_gpios;
...
}
int spi_set_chipselect(struct spi_controller *spi, int cs, int active)
{
/*
* chip-select is not necessary if there is just one device on
* the bus, so gpios = <> are not necessary either */
*/
if (!spi->num_gpios)
return 0;
if (cs > spi->num_gpios)
return -EINVAL;
gpio_set_value(spi->gpios[cs], active);
}
...
unsigned int of_num_gpios(struct device_node *node)
{
unsigned int num = 0;
while (gpio_is_valid(of_get_gpio(node, num)))
num++;
return num;
}
int spi_controller_probe(...)
{
spi_controller *spi;
...
spi->num_gpios = of_num_gpios(node);
if (spi->num_gpios) {
int i = spi->num_gpios;
spi->gpios = kzalloc(sizeof(int) * i, GFP_KERNEL);
if (!spi->gpios)
return -ENOMEM;
do
spi->gpios[i] = of_get_gpio(node, i);
while (!(i--));
}
...
}
--
Anton Vorontsov
email: [EMAIL PROTECTED]
irc://irc.freenode.net/bd2
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