(In reply to Alex Deucher from comment #7)
> (In reply to Jan Ziak from comment #6)
> > (In reply to Alex Deucher from comment #3)
> > > Please attach your xorg log and dmesg output.
> > 
> > Upstream Linux kernel does not support variable mclk on R9 390. I enabled
> > variable mclk by patching some code in drivers/gpu/drm/amd/amdgpu/ (mostly
> > ci_dpm.c).
> 
> What patch(es) did you use?

I added a function based on ci_dpm_force_state_mclk() in ci_dpm.c.

mask is 0x3.

----
static int ci_dpm_force_state_mclk_mask(struct amdgpu_device *adev, u32 mask) {
    struct ci_power_info *pi = ci_get_pi(adev);

    if (!pi->mclk_dpm_key_disabled) {
        PPSMC_Result smc_result =
amdgpu_ci_send_msg_to_smc_with_parameter(adev,
PPSMC_MSG_MCLKDPM_SetEnabledMask, mask);
            printk("[atomsymbol] %s:%d: mask=0x%X, ok=%d\n", __FUNCTION__,
__LINE__, mask, smc_result == PPSMC_Result_OK);
            if (smc_result != PPSMC_Result_OK)
                return -EINVAL;
    }
    return 0;
}
----

/sys/class/drm/card?/device/power_dpm_force_performance_level is set to "auto".