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IVA2.2 Subsystem Basic Programming Model
1. Configure the PRCM to switch on L2:
PRCM.PM_PWSTCTRL_IVA2.SHAREDL2CACHEFLATONSTATE = 0x3.
2. Read back PRCM.PM_PWSTCTRL_IVA2 to ensure that Step 1 is complete.
3. Restore
(j = 0 to 31).
4. Restore
5. Read back PRCM.PM_PWSTCTRL_IVA2 to ensure that Step 4 is complete.
NOTE:
After this sequence, L2$ is empty and content in L2$-SRAM configured as memory-mapped
is lost.
NOTE:
This mode does not provide large power savings, but is provided in IVA2.2 as an enabler for
power-management software development, anticipating that leakage is a major contributor to
power consumption, even in active mode.
5.4.10.5 Video and Sequencer Module Management
5.4.10.5.1 Module Dynamic Power Savings
The video accelerator/sequencer modules implement auto-clock gating to save dynamic power
consumption when no activity is locally detected. For some modules (iME, iLF, iVLCD, sequencer, video
system controller), it is also possible to disable auto-gating by software. Auto-clock gating has no
performance impact.
To optimize local power management, configure the following registers (default values):
•
IVA.
AutoIdle = 1
•
IVA.
AutoIdle = 1
•
IVA.
AutoIdle = 1
•
IVA.
AutoIdle = 1
•
IVA.iVLCD_SYSCONFIG AutoIdle = 1
5.4.10.5.2 System Dynamic Power Savings
For further system dynamic power savings, a module root clock can be independently stopped when the
module has no activity.
The root clock of a module can be stopped by writing 0 in the bit associated with that module in the
IVA.
register. The clock can be stopped, depending on whether the module is
active when it is asked to be stopped. Reading the bit associated with the module in the
IVA.
register lets the user check whether the module clock has effectively been
stopped.
Writing 1 in the bit associated with that module immediately restarts clocks if they are stopped, and makes
the module operational
When stopping the module root clock, take the following precautions:
•
Synchronize with other CPUs/DMAs to determine whether another part of the system requires access
to the module.
•
Check whether the module has dependencies with other modules.
•
Poll the status register in the module to determine whether the module is active.
CAUTION
Invalid configuration of
causes unpredictable results.
801
SWPU177N – December 2009 – Revised November 2010
IVA2.2 Subsystem
Copyright © 2009–2010, Texas Instruments Incorporated
