linux-kernel - Re: [PATCH] devfreq: tegra20: add COMMON

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Message-ID: <CAK8P3a1HOOk48G+-wZGWrM_fg5cn3ytH66qaEU6c7e0BjW+SNw@mail.gmail.com>
Date:   Fri, 28 Jun 2019 14:27:19 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>,
        Linux PM list <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] devfreq: tegra20: add COMMON_CLK dependency

On Fri, Jun 28, 2019 at 1:05 PM Dmitry Osipenko <digetx@...il.com> wrote:
> 28.06.2019 14:00, Dmitry Osipenko пишет:

> >
> > How is it possible to happen? There is a stub for clk_set_min_rate() when COMMON_CLK
> > is disabled .. Could you please show the kernel's config that causes the problem?
> >
> > Moreover that was me who added the missing stub for clk_set_min_rate() in [1] to fix [2].
> >
> > [1]
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/include/linux/clk.h?id=b88c9f4129dcec941e5a26508e991c08051ed1ac
> >
> > [2] https://lists.01.org/pipermail/kbuild-all/2019-April/060292.html
> >
> > So this patch looks wrong to me because apparently it fixes a non-existent problem.
> >
>
> Oh, wait. That was "implicit declaration" and this one is "undefined reference"!
> Still looks like something else need to be fixed..

The stub takes care of the case where there is no CLK support at all, i.e.
CONFIG_HAVE_CLK is disabled. However, some older ARM platforms
still have a custom implementation of the API and lack clk_set_min_rate().

$ git grep -l 'EXPORT_SYMBOL.*\<clk_set_rate\>'  | xargs grep -L
clk_set_min_rate
arch/arm/mach-ep93xx/clock.c
arch/arm/mach-mmp/clock.c
arch/arm/mach-omap1/clock.c
arch/arm/mach-sa1100/clock.c
arch/arm/mach-w90x900/clock.c
arch/c6x/platforms/pll.c
arch/m68k/coldfire/clk.c
arch/mips/ar7/clock.c
arch/mips/bcm63xx/clk.c
arch/mips/lantiq/clk.c
arch/mips/loongson64/lemote-2f/clock.c
arch/mips/ralink/clk.c
arch/unicore32/kernel/clock.c
drivers/sh/clk/core.c

We could in theory convert all of those to COMMON_CLK, or simply add
a dummy clk_set_min_rate() for each one, but since there is only one user,
my fix was simpler.

       Arnd