Hello Markus, Markus Reichl wrote: > Hi Tobias, > > Am 21.11.2016 um 14:33 schrieb Tobias Jakobi: >> Hello everyone, >> >> I was thinking about the following. At the moment we have a suspend OPP >> for cpufreq-dt in place for the Exynos4412 SoC (added in >> 1605b60ad064c7019db8ade07f0b7bdc8c197b93). The rationale behind is that >> the board using the SoC might not have some PMIC reset in place. In case >> the board goes into reboot with a low OPP (i.e. low frequency, but also >> low core voltage), this results in a hang when the first-stage >> bootloaders sets its default core frequency. >> >> So this is properly handled in the kernel just fine, except for some >> corner cases like emergency reboot. >> >> But some time ago devfreq support for the various busses in the >> Exynos4412 was added. On the ODROID boards e.g. this adjust MIF and INT >> voltage. >> >> Let us take the DMC bus. Operating frequency is 100~400MHz and voltage >> is 900~1050mV. >> >> Now let's look at the corresponding board file >> (http://git.denx.de/?p=u-boot.git;a=blob;f=board/samsung/odroid/odroid.c#l234) >> in upstream u-boot. If I read this correctly DMC is set to 400MHz there. >> >> Here's the question. Could this, similar to the cpufreq/core frequency >> issue, pose a problem when the kernel goes into reboot when DMC is on >> the lowest OPP state? >> >> I'm not saying that it does. This just came to my mind during some >> recent discussion. > > Made a test with > # echo performance > /sys/class/devfreq/bus_leftbus/governor > # echo performance > /sys/class/devfreq/bus_dmc/governor > just before reboot. > > 20 out of 20 reboots worked. > > With devfreq simple_ondemand governor around 50% reboots hung. thanks for the tests. I assume by 'reboots hung' you mean that the boot process doesn't even reach u-boot? - Tobias > This could support your thoughts above. > > Servus, > -- > Markus >> >> >> With best wishes, >> Tobias >> -- >> 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 >> > -- > 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 > -- 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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