Re: [PATCH v3 2/3] spi / ACPI: add ACPI enumeration support

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Tuesday, November 20, 2012 03:15:25 PM Mika Westerberg wrote:
> On Tue, Nov 20, 2012 at 02:05:26PM +0100, Rafael J. Wysocki wrote:
> > On Tuesday, November 20, 2012 12:29:43 PM Mika Westerberg wrote:
> > > ACPI 5 introduced SPISerialBus resource that allows us to enumerate and
> > > configure the SPI slave devices behind the SPI controller. This patch adds
> > > support for this to the SPI core.
> > > 
> > > In addition we bind ACPI nodes to SPI devices. This makes it possible for
> > > the slave drivers to get the ACPI handle for further configuration.
> > > 
> > > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > > ---
> > >  drivers/spi/spi.c |  115 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 114 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> > > index 84c2861..3ae5351 100644
> > > --- a/drivers/spi/spi.c
> > > +++ b/drivers/spi/spi.c
> > > @@ -35,6 +35,8 @@
> > >  #include <linux/sched.h>
> > >  #include <linux/delay.h>
> > >  #include <linux/kthread.h>
> > > +#include <linux/ioport.h>
> > > +#include <linux/acpi.h>
> > >  
> > >  static void spidev_release(struct device *dev)
> > >  {
> > > @@ -93,6 +95,10 @@ static int spi_match_device(struct device *dev, struct device_driver *drv)
> > >  	if (of_driver_match_device(dev, drv))
> > >  		return 1;
> > >  
> > > +	/* Then try ACPI */
> > > +	if (acpi_driver_match_device(dev, drv))
> > > +		return 1;
> > > +
> > >  	if (sdrv->id_table)
> > >  		return !!spi_match_id(sdrv->id_table, spi);
> > >  
> > > @@ -888,6 +894,112 @@ static void of_register_spi_devices(struct spi_master *master)
> > >  static void of_register_spi_devices(struct spi_master *master) { }
> > >  #endif
> > >  
> > > +#ifdef CONFIG_ACPI
> > > +static int acpi_spi_add_resource(struct acpi_resource *ares, void *data)
> > > +{
> > > +	struct acpi_resource_spi_serialbus *sb;
> > > +	struct spi_device *spi = data;
> > > +	struct resource r;
> > > +
> > > +	switch (ares->type) {
> > > +	case ACPI_RESOURCE_TYPE_IRQ:
> > > +	case ACPI_RESOURCE_TYPE_EXTENDED_IRQ:
> > 
> > It is not necessary to check the resource type for IRQ resources here,
> > because acpi_dev_resource_interrupt() will do it for you anyway. :-)
> > 
> > So, I would first check if the resource type is ACPI_RESOURCE_TYPE_SERIAL_BUS
> > (and populate the spi_device fields if so) and then do something like this:
> > 
> > if (acpi_dev_resource_interrupt(ares, 0, &r)) {
> > 	if (spi->irq < 0)
> > 		spi->irq = r.start;
> > 
> > 	return 1;
> > }
> > 
> > We don't even need to memset(), because we're not going to use that resource
> > object going forward.
> 
> But doesn't acpi_dev_resource_interrupt() do acpi_register_gsi() and all
> that stuff? And we were supposed to avoid that.

Right.

So, because the function will always return 1 anyway, you can do

if (spi->irq < 0) {
	struct resource r;

	if (acpi_dev_resource_interrupt(ares, 0, &r))
		spi->irq = r.start;
}

after checking the ACPI_RESOURCE_TYPE_SERIAL_BUS type.

> > 
> > > +		/* Only use the first interrupt resource and skip the rest */
> > > +		memset(&r, 0, sizeof(r));
> > > +		if (spi->irq < 0 && acpi_dev_resource_interrupt(ares, 0, &r))
> > > +			spi->irq = r.start;
> > > +		return 1;
> > > +
> > > +	case ACPI_RESOURCE_TYPE_SERIAL_BUS:
> > > +		sb = &ares->data.spi_serial_bus;
> > > +		if (sb->type == ACPI_RESOURCE_SERIAL_TYPE_SPI) {
> > > +			spi->chip_select = sb->device_selection;
> > > +			spi->max_speed_hz = sb->connection_speed;
> > > +
> > > +			if (sb->clock_phase == ACPI_SPI_SECOND_PHASE)
> > > +				spi->mode |= SPI_CPHA;
> > > +			if (sb->clock_polarity == ACPI_SPI_START_HIGH)
> > > +				spi->mode |= SPI_CPOL;
> > > +			if (sb->device_polarity == ACPI_SPI_ACTIVE_HIGH)
> > > +				spi->mode |= SPI_CS_HIGH;
> > > +
> > > +			return 1;
> > > +		}
> > > +		return 0;
> > > +	}
> > > +
> > > +	return 0;
> > 
> > We're not interested in any resources except for the above, so I think we
> > can just always return 1 from this function, or am I missing anything?
> 
> Right you are, we can return 1 always. I'll update this.
> 
> > > +}
> > > +
> > > +static acpi_status acpi_spi_add_device(acpi_handle handle, u32 level,
> > > +				       void *data, void **return_value)
> > > +{
> > > +	struct spi_master *master = data;
> > > +	struct list_head resource_list;
> > > +	struct acpi_device *adev;
> > > +	struct spi_device *spi;
> > > +	int ret;
> > > +
> > > +	if (acpi_bus_get_device(handle, &adev))
> > > +		return AE_OK;
> > > +	if (acpi_bus_get_status(adev) || !adev->status.present)
> > > +		return AE_OK;
> > > +
> > > +	spi = spi_alloc_device(master);
> > > +	if (!spi) {
> > > +		dev_err(&master->dev, "failed to allocate SPI device for %s\n",
> > > +			dev_name(&adev->dev));
> > > +		return AE_NO_MEMORY;
> > > +	}
> > > +
> > > +	ACPI_HANDLE_SET(&spi->dev, handle);
> > > +	spi->irq = -1;
> > > +
> > > +	INIT_LIST_HEAD(&resource_list);
> > > +	ret = acpi_dev_get_resources(adev, &resource_list,
> > > +				     acpi_spi_add_resource, spi);
> > 
> > acpi_dev_free_resource_list(&resource_list); can be done here (the list
> > is going to be empty anyway if acpi_spi_add_resource() always returns 1)
> > and then you won't need the fail_put_dev label.
> 
> OK, but there are still two cases below where we need to do
> spi_dev_put(spi). Or do you mean that for each case I just call that
> directly instead of goto fail_put_dev?

Yes, that's what I meant.  I'd just do

if (ret < 0 || !spi->max_speed_hz) {
	spi_dev_put(spi);
	return AE_OK;
}

> > > +	if (ret < 0)
> > > +		goto fail_put_dev;
> > > +
> > > +	acpi_dev_free_resource_list(&resource_list);
> > > +
> > > +	if (!spi->max_speed_hz)
> > > +		goto fail_put_dev;
> > > +
> > > +	strlcpy(spi->modalias, dev_name(&adev->dev), sizeof(spi->modalias));
> > > +	if (spi_add_device(spi)) {
> > > +		dev_err(&master->dev, "failed to add SPI device %s from ACPI\n",
> > > +			dev_name(&adev->dev));
> > > +		goto fail_put_dev;
> > > +	}
> > > +
> > > +	return AE_OK;
> > > +
> > > +fail_put_dev:
> > > +	spi_dev_put(spi);
> > > +
> > > +	return AE_OK;
> > > +}
> > > +
> > > +static void acpi_register_spi_devices(struct spi_master *master)
> > > +{
> > > +	acpi_status status;
> > > +	acpi_handle handle;
> > > +
> > > +	handle = ACPI_HANDLE(&master->dev);
> > > +	if (!handle)
> > > +		return;
> > > +
> > > +	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
> > > +				     acpi_spi_add_device, NULL,
> > > +				     master, NULL);
> > > +	if (ACPI_FAILURE(status))
> > > +		dev_warn(&master->dev, "failed to enumerate SPI slaves\n");
> > > +}
> > > +#else
> > > +static inline void acpi_register_spi_devices(struct spi_master *master) {}
> > > +#endif /* CONFIG_ACPI */
> > > +
> > >  static void spi_master_release(struct device *dev)
> > >  {
> > >  	struct spi_master *master;
> > > @@ -1023,8 +1135,9 @@ int spi_register_master(struct spi_master *master)
> > >  		spi_match_master_to_boardinfo(master, &bi->board_info);
> > >  	mutex_unlock(&board_lock);
> > >  
> > > -	/* Register devices from the device tree */
> > > +	/* Register devices from the device tree and ACPI */
> > >  	of_register_spi_devices(master);
> > > +	acpi_register_spi_devices(master);
> > >  done:
> > >  	return status;
> > >  }

Thanks,
Rafael


-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.