On Tue, Dec 08, 2015 at 10:26:49AM +0000, Jon Hunter wrote:
> Enabling CPUFreq support for Tegra124 Chromebooks is causing the Tegra124
> to hang when resuming from suspend.
>
> When CPUFreq is enabled, the CPU clock is changed from the PLLX clock to
> the DFLL clock during kernel boot. When resuming from suspend the CPU
> clock is temporarily changed back to the PLLX clock before switching back
> to the DFLL. If the DFLL is operating at a much lower frequency than the
> PLLX when we enter suspend, and so the CPU voltage rail is at a voltage
> too low for the CPUs to operate at the PLLX frequency, then the device
> will hang.
>
> Please note that the PLLX is used in the resume sequence to switch the CPU
> clock from the very slow 32K clock to a faster clock during early resume
> to speed up the resume sequence before the DFLL is resumed.
>
> Ideally, we should fix this by setting the suspend frequency so that it
> matches the PLLX frequency, however, that would be a bigger change. For
> now simply disable CPUFreq support for Tegra124 Chromebooks to avoid the
> hang when resuming from suspend.
>
> Fixes: 9a0baee960a7 ("ARM: tegra: Enable CPUFreq support for Tegra124
> Chromebooks")
>
> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
> ---
>
> Please note that this fix is required for v4.4
Since I saw this mentioned on IRC, I applied it directly to the arm-soc
fixes branch.
Thanks,
-Olof
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