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

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Message-ID: <06bab5c5-e9fd-4741-bab7-6b199cfac18a@leemhuis.info>
Date: Mon, 14 Oct 2024 08:45:34 +0200
From: Thorsten Leemhuis <regressions@...mhuis.info>
To: Jay Buddhabhatti <jay.buddhabhatti@....com>
Cc: Greg KH <gregkh@...uxfoundation.org>,
 Linux kernel regressions list <regressions@...ts.linux.dev>,
 Sasha Levin <sashal@...nel.org>, Stephen Boyd <sboyd@...nel.org>,
 Joel GUITTET <jguittet.opensource@...ekio.com>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: Bad commit backported on the v5.15.y branch ?

On 11.10.24 10:48, Joel GUITTET wrote:
> 
> 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.

FWIW, that is 1fe15be1fb6135 ("drivers: clk: zynqmp: update divider
round rate logic") [v6.8-rc1].

> Is anybody reading this message able to answer why it was
> backported ?

Looks like because it fixes a bug. I CCed the original author and those
that handled the patch, maybe they can help us out and tell us what's
the best strategy forward here.

> 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.
Does 6.12-rc work fine for you? Because if not, we should fix the
problem there.

Ciao, Thorsten