OMAP3430ES2+ introduces a new feature: optional powerdomain context
hardware save-and-restore (SAR).  Currently, this feature only applies
to USBHOST and USBTLL module context when the USBHOST or CORE
powerdomains enter a low-power sleep state[1].  This feature avoids
re-enumeration of USB devices when the powerdomains return from idle,
which is potentially time-consuming.

This patch adds support for enabling and disabling hardware
save-and-restore to the powerdomain code.  Three new functions are
added, pwrdm_enable_hdwr_sar(), pwrdm_disable_hdwr_sar(), and
pwrdm_can_hdwr_sar().  A new struct powerdomain "flags" field is
added, with a PWRDM_HAS_HDWR_SAR flag to indicate powerdomains with
SAR support.

Thanks to Jouni Högander <jouni.hogander@nokia.com> for reviewing an
earlier version of these patches, and Richard Woodruff <r-woodruff2@ti.com>
for clarifying the purpose of these bits.

1.  For the USBHOST controller module, context loss occurs when the
    USBHOST powerdomain enters off-idle.  For USBTLL, context loss
    occurs either if CORE enters off-idle, or if the CORE logic is
    configured to turn off when CORE enters retention-idle (OSWR).
    34xx ES2 TRM 4.8.6.1.1, 4.8.6.1.2
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Thie patch adds code to the powerdomain layer to track the
clockdomains associated with each powerdomain.

It also modifies the clockdomain code to register clockdomains
with their corresponding powerdomain when the clockdomain is registered.
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>

This patch creates an interface to the powerdomain registers in the
PRM/CM modules on OMAP2/3.  This interface is intended to be used by
PM code, e.g., pm.c; not by device drivers directly.

Each powerdomain will be defined in later patches as static
structures.  Also defined are dependencies between powerdomains,
used for adding and removing PM_WKDEP and CM_SLEEPDEP bits.  The
powerdomain structures are linked into a list at boot by
pwrdm_register(), similar to the OMAP clock code.

The patch adds a Kconfig option, CONFIG_OMAP_DEBUG_POWERDOMAIN, which
when enabled will emit verbose debug messages via pr_debug().
Signed-off-by: NPaul Walmsley <paul@pwsan.com>
Signed-off-by: NTony Lindgren <tony@atomide.com>