Hi Mike,
Since commit 9b6a3f3633a5cc9("coresight: etmv4: Fix CPU power management setup in probe() function"), ETM probe fails consistently like below:
localhost ~ # dmesg | grep -i etm [ 6.460602] coresight-etm4x: probe of 7040000.etm failed with error -16 [ 6.524756] coresight etm1: CPU1: ETM v4.2 initialized [ 6.531152] coresight etm2: CPU2: ETM v4.2 initialized [ 6.538495] coresight etm3: CPU3: ETM v4.2 initialized [ 6.545124] coresight etm4: CPU4: ETM v4.2 initialized [ 6.552904] coresight etm5: CPU5: ETM v4.2 initialized [ 6.559714] coresight etm6: CPU6: ETM v4.2 initialized [ 6.569596] coresight etm7: CPU7: ETM v4.2 initialized localhost ~ #
Most of the time its for ETM0 but I occasionally see ETM1 and other ETMs failing to probe, but the some ETM probe failure is always there. I'm using SC7180 based platform on 5.4 kernel which has all the coresight patches backported.
If I revert that commit, I don't see the issue at all. In case you can identify something which might be causing this, please let me know. I'm planning to look into this as well in the meantime.
Thanks, Sai