[PATCH 1/4 v4] of_spi: add generic binding support to specify cs gpio
Jean-Christophe PLAGNIOL-VILLARD
plagnioj at jcrosoft.com
Fri Mar 9 13:02:32 EST 2012
On 08:14 Fri 09 Mar , Grant Likely wrote:
> On Wed, 7 Mar 2012 13:23:06 +0100, Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com> wrote:
> > 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.
> >
> > Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
> > Cc: devicetree-discuss at lists.ozlabs.org
> > Cc: spi-devel-general at lists.sourceforge.net
> > ---
> > v4:
> > use cs_gpio to pass the gpio number
> >
> > Best Regards,
> > J.
> > Documentation/devicetree/bindings/spi/spi-bus.txt | 6 ++
> > drivers/spi/spi.c | 57 +++++++++++++++++++-
> > include/linux/spi/spi.h | 6 ++
> > 3 files changed, 66 insertions(+), 3 deletions(-)
> >
> > diff --git a/Documentation/devicetree/bindings/spi/spi-bus.txt b/Documentation/devicetree/bindings/spi/spi-bus.txt
> > index e782add..c253379 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
> > @@ -21,6 +22,8 @@ assumption that board specific platform code will be used to manage
> > chip selects. Individual drivers can define additional properties to
> > support describing the chip select layout.
> >
> > +If cs-gpios is used the number of chip select will automatically increased.
> > +
> > SPI slave nodes must be children of the SPI master node and can
> > contain the following properties.
> > - reg - (required) chip select address of device.
> > @@ -34,6 +37,9 @@ 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 controller_data
> > +
> > SPI example for an MPC5200 SPI bus:
> > spi at f00 {
> > #address-cells = <1>;
> > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> > index b2ccdea..c1d0955 100644
> > --- a/drivers/spi/spi.c
> > +++ b/drivers/spi/spi.c
> > @@ -28,6 +28,7 @@
> > #include <linux/mod_devicetable.h>
> > #include <linux/spi/spi.h>
> > #include <linux/of_spi.h>
> > +#include <linux/of_gpio.h>
> > #include <linux/pm_runtime.h>
> > #include <linux/export.h>
> >
> > @@ -322,6 +323,7 @@ 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;
> > }
> > @@ -339,15 +341,16 @@ 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;
> > }
> >
> > @@ -371,6 +374,13 @@ int spi_add_device(struct spi_device *spi)
> > goto done;
> > }
> >
> > + if (master->num_gpio_cs &&
> > + spi->chip_select >= master->first_gpio_cs) {
> > + int num = spi->chip_select - master->first_gpio_cs;
> > +
> > + spi->cs_gpio = master->cs_gpios[num];
>
> spi->cs_gpio isn't used anywhere.
driver
as example atmel spi
I choose to let the driver to manage it as they may need to manange specific
register when using both hw and gpio cs
>
> > + }
> > +
> > /* 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...
> > @@ -561,6 +571,43 @@ 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");
> > +
> > + if (nb < 1)
> > + return 0;
> > +
> > + cs = devm_kzalloc(&master->dev, sizeof(int) * nb, GFP_KERNEL);
> > + master->cs_gpios = cs;
> > +
> > + if (!master->cs_gpios)
> > + return -ENOMEM;
> > +
> > + master->first_gpio_cs = master->num_chipselect;
> > + master->num_chipselect += nb;
> > + master->num_gpio_cs = nb;
>
> I think this can be simplified. Rather than trying to optimize by having
> a set of integrated cs lines followed by a gpio set, I think it would be
> better to have a single cs_gpios table that covers the whole range of
> num_chipselect; even if they overlap natural cs lines. That will make for
> an easier to use binding since users won't need to remember how many natural
> cs lines are on the device when filling the cs-gpios property. It will
> also make the code simpler because first_gpio_cs and num_gpio_cs can both
> be eliminated. It also means the core can have exact knowledge about which
> gpio is associated with which cs number.
ok why not so I feel the array with -EINVAL for hw cs;
Best Regards,
J.
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