This patch allows the UART clocks to be disabled when the OMAP UARTs
are inactive, thus permitting the chip to hit retention in idle.
After the expiration of an activity timer, each UART is allowed to
disable its clocks so the system can enter retention. The activity
timer is (re)activated on any UART interrupt, UART wake event or any
IO pad wakeup. The actual disable of the UART clocks is done in the
'prepare_idle' hook called from the OMAP idle loop.
While the activity timer is active, the smart-idle mode of the UART is
also disabled. This is due to a "feature" of the UART module that
after a UART wakeup, the smart-idle mode may be entered before the
UART has communicated the interrupt, or upon TX, an idle mode may be
entered before the TX FIFOs are emptied.
Upon suspend, the 'prepare_suspend' hook cancels any pending activity
timers and allows the clocks to be disabled immediately.
In addition, upon disabling clocks the UART state is saved in case
of an off-mode transition while clocks are off.
Special thanks to Tero Kristo for the initial ideas and first versions
of UART idle support, and to Jouni Hogander for extra testing and
bugfixes.
Tested on OMAP3 (Beagle, RX51, SDP, EVM) and OMAP2 (n810)
Cc: Tero Kristo <tero.kristo@nokia.com>
Cc: Jouni Hogander <jouni.hogander@nokia.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
This patch is to sync the core linux-omap PM code with mainline. This
code has evolved and been used for a while the linux-omap tree, but
the attempt here is to finally get this into mainline.
Following this will be a series of patches from the 'PM branch' of the
linux-omap tree to add full PM hardware support from the linux-omap
tree.
Much of this PM core code was written by Jouni Hogander with
significant contributions from Paul Walmsley as well as many others
from Nokia, Texas Instruments and linux-omap community.
Signed-off-by: Jouni Hogander <jouni.hogander@nokia.com>
Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
