Add base debugfs mechanism for SoundWire bus by creating soundwire
root and master-N and slave-x hierarchy.

Also add SDW Slave SCP, DP0 and DP-N register debug file.

Registers not implemented will print as "XX"

Credits: this patch is based on an earlier internal contribution by
Vinod Koul, Sanyog Kale, Shreyas Nc and Hardik Shah.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Sanyog Kale <sanyog.r.kale@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20190821185821.12690-2-pierre-louis.bossart@linux.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Use Linux style

Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The limitation of being able to check only for -EPROBE_DEFER from
dev_pm_domain_attach() has been removed. Hence let's respect all error
codes and bail out accordingly.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

MIPI Discovery And Configuration (DisCo) Specification for SoundWire
specifies properties to be implemented for SoundWire Masters and
Slaves. The DisCo spec doesn't mandate these properties. However,
SDW bus cannot work without knowing these values.

The helper functions read the Master and Slave properties.
Implementers of Master or Slave drivers can use any of the below
three mechanisms:
   a) Use these APIs here as .read_prop() callback for Master
      and Slave
   b) Implement own methods and set those as .read_prop(), but invoke
      APIs in this file for generic read and override the values with
      platform specific data
   c) Implement ones own methods which do not use anything provided
      here

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Acked-By: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This adds the base SoundWire bus type, bus and driver registration.
along with changes to module device table for new SoundWire
device type.

Signed-off-by: Sanyog Kale <sanyog.r.kale@intel.com>
Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com>
Acked-By: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>