On Mon, Apr 12, 2010 at 09:55:28PM +0900, jassi brar wrote: > On Mon, Apr 12, 2010 at 6:39 PM, Lukasz Majewski <l.majewski@xxxxxxxxxxx> wrote: > > One approach to solve the problem, and therefore deliver power savings, > > is to modify the ALSA driver and provide a switch to inform the CPU IDLE > > framework that it should now use the DEEP IDLE instead of IDLE when entering > > the Low Power Audio playback mode is expected. This change may be performed > > by replacing the method for entering the IDLE mode to DEEP IDLE. Moreover > > some sources immune to power gating (like e.g. RTC timer) have to be used > > for waking up. The biggest problem for this approach is the kernel's policy > > violation, that no user program should directly change scheduling/idle > > policy. > Actually any power saving mode is transparent to the LPAM(LowPowerAudioMode). > "LPAM h/w" is simply an I2S controller with an additional 'overlay' > stereo channel > which is h/w-mix'ed with the first two of the 6 channels. And these overlay > channels works just as well in normal power mode. LPAM is but one > ramification of > of the platform using the interrupt as a wakeup source. It is also used for > low latency playback like 'alerts' and 'alarms'. > Our LPAM doesn't work right away not because of the power management stack > but because ASoC can't yet handle a > codec-active-in-system-suspended-mode scenario. > So, I too think it's a bad idea to hack core PM for things like LPAM. > > > So what is your opinion about integrating use of the DEEP IDLE state mode > > in the scheduler (either as new scheduling policy or modifying scheduler > > code)? > imho, such 'variation' in suspend had better be implemented in > platform specific manner. > Just because samsung's manual call it deep-IDLE doesn't make it an 'IDLE' mode. > It is closer to suspend than idle, at least to me. It does seem to be a form of suspend, as it halts the SDRAM and powers down the ARM core... this means that there's a whole pile of stuff that needs to be considered before allowing the system to go into such a state. -- Ben Q: What's a light-year? A: One-third less calories than a regular year. -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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