On Mon, 6 Jan 2014 00:00:00 +0200 Siarhei Siamashka <[email protected]> wrote:
> A better solution is to really ramp up the CPU to the maximum clock > speed if we have some external power source connected (ACIN or VBUS). > Adhering to the "principle of least surprise", it makes sense to fork > the "ondemand" governor with some new name and make it the default. A new governor (and a platform-specific one, no less) is unlikely to ever be mainlined. Try mainlining those "fantasy" or "interactive", you'll more likely be <del>laughed out of the building</del> politely pointed to all the tunables of "ondemand", some of which I just listed in my other E-Mail. If you *really* want to react to power events, there is no reason a userspace program can't change max/min_frequency of the ondemand governor, or even switch between ondemand and performance as the power situation allows; it could be either a daemon or a oneshot script called from udev(?), if changes are only required on plugging/unplugging of power source. In fact I think there should be something like that already (designed for laptops). > The users will be able to lookup the name of this new governor in > google and find linux-sunxi wiki with the detailed explanations > about how it works :-) Now what it really should do: > 1. It can subscribe to the notifications from AXP209 about > plugging/unplugging the external power sources and run the CPU > at the maximum speed when external power is available. > This should solve all the performance issues for the > development boards and any devices running from the external > power sources. I believe that this is exactly the primary use > case for the vast majority of linux-sunxi users :-) > 2. It might include the tweaks from http://linux-sunxi.org/Cpufreq > in the case if they are confirmed to be useful when running on > a battery. > 3. In the case if we have only microusb connected and can take only > 500 mA from it, then we might be interested in preventing the > battery from eventually getting drained. As we know, even the > CPU alone can cause more than 500 mA consumption if really > stressed. The cpufreq governor may try to limit the maximum > CPU clock speed if the LiPo battery charge is low and only > microusb is connected for charging it. > 4. Maybe do something to prevent SoC overheating if CPU, Mali and > Cedar are all used at the same time? AXP209 has some ADC and we > might try to limit the CPU / Mali / Cedar clock frequencies > if the power drain is too high. But the properly working thermal > sensor in A10 / A20 (if it exists) would be of course a better > solution. -- With respect, Roman
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