linux-kernel - Re: [PATCH] ASoC: remove NULL pointer check for clk_disable

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Message-ID: <CAK7LNATFZjKkCtb1CQb6NdHEZAra6AqzqBW2i8QJgiLWt4eHzg@mail.gmail.com>
Date:   Sun, 21 May 2017 03:50:33 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>
Cc:     alsa-devel@...a-project.org, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Fabio Estevam <fabio.estevam@....com>,
        patches@...nsource.wolfsonmicro.com,
        Sangbeom Kim <sbkim73@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        Timur Tabi <timur@...i.org>, Mark Brown <broonie@...nel.org>,
        Support Opensource <support.opensource@...semi.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Xiubo Li <Xiubo.Lee@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        linuxppc-dev@...ts.ozlabs.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        Nicolin Chen <nicoleotsuka@...il.com>
Subject: Re: [PATCH] ASoC: remove NULL pointer check for clk_disable_unprepare

2017-05-21 3:42 GMT+09:00 Masahiro Yamada <yamada.masahiro@...ionext.com>:
> Hi Krzysztof,
>
>
> 2017-05-21 3:04 GMT+09:00 Krzysztof Kozlowski <krzk@...nel.org>:
>> On Sun, May 21, 2017 at 02:42:38AM +0900, Masahiro Yamada wrote:
>>> After long term efforts of fixing non-common clock implementations,
>>> clk_disable() is a no-op for a NULL pointer input, and this is now
>>> tree-wide consistent.
>>>
>>> All clock consumers can safely call clk_disable(_unprepare) without
>>> NULL pointer check.
>>>
>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>>> ---
>>>
>>>  sound/soc/codecs/adau17x1.c                | 3 +--
>>>  sound/soc/codecs/da7213.c                  | 3 +--
>>>  sound/soc/codecs/da7218.c                  | 3 +--
>>>  sound/soc/codecs/da7219-aad.c              | 5 ++---
>>>  sound/soc/codecs/da7219.c                  | 3 +--
>>>  sound/soc/codecs/es8328.c                  | 3 +--
>>>  sound/soc/codecs/wm8731.c                  | 3 +--
>>>  sound/soc/davinci/davinci-evm.c            | 3 +--
>>>  sound/soc/fsl/imx-audmux.c                 | 6 ++----
>>>  sound/soc/intel/boards/bytcr_rt5640.c      | 2 +-
>>>  sound/soc/intel/boards/cht_bsw_rt5645.c    | 3 +--
>>>  sound/soc/mediatek/mt8173/mt8173-afe-pcm.c | 6 ++----
>>>  sound/soc/samsung/i2s.c                    | 3 +--
>>>  13 files changed, 16 insertions(+), 30 deletions(-)
>>>
>>
>> (...)
>>
>>> diff --git a/sound/soc/samsung/i2s.c b/sound/soc/samsung/i2s.c
>>> index af3ba4d..3a06acd 100644
>>> --- a/sound/soc/samsung/i2s.c
>>> +++ b/sound/soc/samsung/i2s.c
>>> @@ -1122,8 +1122,7 @@ static int i2s_runtime_suspend(struct device *dev)
>>>       i2s->suspend_i2scon = readl(i2s->addr + I2SCON);
>>>       i2s->suspend_i2spsr = readl(i2s->addr + I2SPSR);
>>>
>>> -     if (i2s->op_clk)
>>> -             clk_disable_unprepare(i2s->op_clk);
>>> +     clk_disable_unprepare(i2s->op_clk);
>>>       clk_disable_unprepare(i2s->clk);
>>
>> I think the check in i2s_runtime_resume() should be removed then as well
>> to keep it symmetrical. Otherwise it looks suspicious.
>
>
> Hmm, you have a point.  We will lose the symmetry.
>
> If samsung/i2s.c is only used with the common clock framework,
> we can omit the NULL pointer check for clk_prepare_enable()
> because it is also a no-op for NULL clk input
> (it returns 0).
>
> At this moment, this is not consistent for non-common clock implementations,
> though.


I retract this patch.



-- 
Best Regards
Masahiro Yamada