Hi Tony, I have few more questions on OMAP3: 1) As you know there are power scripts in drivers/mfd folder for PMIC chip (Triton2). Is this mandatory to use these scripts like there are P1,P2,P3 areas are there in PMIC. 2) My understanding was when regulator_enable and disable are called from device drivers, voltage regulators are powered on/off, is it correct, if yes, why do we need to use power scripts? 3) Suppose HiFreq clk source (Oscillator), since there are no suspend/resume hooks from PMIC. Do we mandatory to use these scripts during suspend to RAM or we can directly power off oscillators or is there any hardware mechanism also, when all voltage regulators are disabled, HiFreq oscillator will be cut off. 4) Do power scripts are mandatory for all OMAP platforms? Regards, d. raj > Date: Thu, 14 Aug 2014 07:09:43 -0700 > From: tony@xxxxxxxxxxx > To: draj187@xxxxxxxxxxx > CC: linux-omap@xxxxxxxxxxxxxxx > Subject: Re: Questions about enabling dps(dynamic power switching) and SLM > > * Deepa Raj <draj187@xxxxxxxxxxx> [140813 06:16]: >> Hi, >> >> I am working on OMAP3 and OMaP4. I know we can do AVS by smartreflex. The Questions are as follows: >> >> 1) I have gone through TRM but could not find how can we enable/disable dps and slm. Can you please point out how can we do that? > > With the mainline tree we currently have omap3 working for DPS. > For omap4 and later, features are not working at least not yet. > To play with omap3 dps with mainline kernel, you need to consider > the following: > > 1. Start with a board that's known to work, like beagleboard xm > > 2. Start with omap2plus_defconfig, keep EHCI disabled, and OTG cable > disconnected > > 3. Enable UART timeouts and off-idle on the device with something like > > #!/bin/bash > > uarts=$(find /sys/class/tty/ttyO*/device/power/ -type d) > for uart in $uarts; do > echo 3000> $uart/autosuspend_delay_ms > done > > uarts=$(find /sys/class/tty/ttyO*/power/ -type d) > for uart in $uarts; do > echo enabled> $uart/wakeup > echo auto> $uart/control > done > > echo 1> /sys/kernel/debug/pm_debug/enable_off_mode > > Also the screen needs to be blanked if you have one. Once > the system starts hitting deeper idle states, you can see > that set off values in /sys/kernel/debug/pm_debug/count. > >> 2) Does DPS and SLM only applies to MPU,IVA and core domains or it applies to all devices? > > We are now cutting off all voltages during idle if the twl4030 > configuration is enabled with ti,twl4030-power-idle-osc-off > in the board specific .dts file. > >> 3) According to OMAP ppt, DPS (similar like run time power management and having wakeup latency in micro seconds). If we enable DPS, does hardware take care of switching on/off power domains means there is no need of powering on/off devices through software? > > Right, the devices will idle and save and restore their > state using runtime PM. Once all the blocking devices are > idle, the system will automatically start entering deeper > idle states. > >> 4) Will DPS only triggers to retention state only or off state also? > > Both work, depending on if /sys/kernel/debug/pm_debug/enable_off_mode > is enabled or not. > >> 5) If we enable SLM (according to omap ppt, suspend to ram) but wakeup latencies in milliseconds, if we enable this feature, does the hardware be able to power off all the devices when system is idle or it only applies to VDD1 (MPU-IVA) or VDD2 (Core domain)? > > What is automatically powered down depends on the twl4030 script > configuration, see for example omap3_idle_rconfig. For omap4, > and later the twl6040 control is only over I2C4 AFAIK. > >> Hope to see answers from experts. > > Hopefully that will get you started :) > > Regards, > > Tony > -- > To unsubscribe from this list: send the line "unsubscribe linux-omap" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
