APQ8096: Need to port patches for random boot failure issue, from kernel version 5.7.19 to 4.14.96

Hi,

We have some frequency stability issue in kernel release version 4.14.96, we have also created Frequency switching stability issues on Q820 thread previously. After applying changes suggested by @Loic in https://git.linaro.org/people/loic.poulain/linux.git/log/?h=qcomlt-4.14-820c-voltage-scaling branch, our cpufreq-bench issue got resolved but there is still a random boot failure issue.

We have tested kernel version 5.7.19 and it seems in this kernel version, random boot stuck issue got resolved (haven’t tested cpufreq-bench yet), we have tested approx. 70 hour reboot test and haven’t observed boot failure issue.

Now our condition is that we have released our product on 4.14.96 kernel and don’t want to upgrade whole kernel at this stage. So we want to know some path where we can port changes which solved this random boot failure issue. It will really helpful if we get to know specific patches or branch in which this issue was resolved.

Thanks,
Hiren

I looked into backporting the changes some time ago, and the conclusion I came to was that it wasn’t feasible – much less work involved in moving forward to 5.4, which is an LTS release and free of the boot failure problem.

Any particular reason it would be a huge challenge for you to use a newer kernel?

Hi @Hiren , unfortunately I don’t know which change fixed the boot issue, it would request some git bisecting… I would suggest moving to 5.4 or up. An other solution (workaround) would be to disable ramdump/download mode, which prevents the board to reboot normally when the boot issue occurs, this requests a tiny change in the XBL bootloader (closed source) to discard boot_dload mode.

Hi, Sorry for late response. @doitright we are checking with our customer to use latest kernel and why they don’t want to upgrade kernel.

@Loic we already gives bypass ramdump mode workaround to our customer but now they also want to fix this issue in 4.14.96 kernel, so we are looking for some patches which could possibly resolve this issue.