• Jon Hunter's avatar
    ARM: tegra: Fix suspend hang on Tegra124 Chromebooks · 80373d37
    Jon Hunter authored
    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: 9a0baee9 ("ARM: tegra: Enable CPUFreq support for Tegra124
    		      Chromebooks")
    Signed-off-by: default avatarJon Hunter <jonathanh@nvidia.com>
    Signed-off-by: default avatarOlof Johansson <olof@lixom.net>
    80373d37
tegra124-nyan.dtsi 15.7 KB