linux-kernel - Bad commit backported on the v5.15.y branch ?

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Message-ID:
 <AM9P192MB1316ABE1A8E1D41C4243F596D7792@AM9P192MB1316.EURP192.PROD.OUTLOOK.COM>
Date: Fri, 11 Oct 2024 08:48:39 +0000
From: Joel GUITTET <jguittet.opensource@...ekio.com>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Bad commit backported on the v5.15.y branch ?

Hello,

I faced some issue related to scaling frequency on ZynqMP device using v5.15.167 kernel.
As an exemple setting the scaling frequency below show it's not properly set:

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_available_frequencies
299999 399999 599999 1199999

echo 399999 > /sys/devices/system/cpu/cpufreq/policy0/scaling_setspeed

cat /sys/devices/system/cpu/cpufreq/policy0/scaling_cur_freq
399999

cat /sys/devices/system/cpu/cpufreq/policy0/cpuinfo_cur_freq
299999 ====> Should be 399999

After analysis of this issue with the help of Xilinx, it appears that a commit was backported on the 5.15.y branch, but probably it should not, or not as is. The commit is 9117fc44fd3a9538261e530ba5a022dfc9519620 modifying drivers/clk/zynqmp/divider.c.

Is anybody reading this message able to answer why it was backported ? The information I have until now is that it is intended recent kernel version. Dependencies for this modification is currently under clarification with Xilinx (maybe another commit to backport).

By the way, reverting this commit fix the issue shown above.

Thanks for the feedback,
Joel