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References: <20230307115022.12846-2-zhuyinbo@loongson.cn> <202303082037.QPfBP64A-lkp@intel.com> <b94ee1d2-b224-f9d5-3f3c-0096634f4c93@loongson.cn> <ec1fb4d134181a1b1859bcb884dcd494.sboyd@kernel.org> <c03e47f7-bb26-0114-b300-357634b0e581@kernel.org>
Subject: Re: [PATCH v13 2/2] clk: clk-loongson2: add clock controller driver support
From:   Stephen Boyd <sboyd@kernel.org>
Cc:     oe-kbuild-all@lists.linux.dev, Jianmin Lv <lvjianmin@loongson.cn>,
        Liu Peibao <liupeibao@loongson.cn>, wanghongliang@loongson.cn,
        loongson-kernel@lists.loongnix.cn
To:     Krzysztof Kozlowski <krzk@kernel.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org,
        kernel test robot <lkp@intel.com>, linux-clk@vger.kernel.org,
        linux-kernel@vger.kernel.org, zhuyinbo <zhuyinbo@loongson.cn>
Date:   Mon, 13 Mar 2023 11:20:10 -0700
User-Agent: alot/0.10
Precedence: bulk

Quoting Krzysztof Kozlowski (2023-03-10 00:42:47)
> On 10/03/2023 00:47, Stephen Boyd wrote:
> > Quoting zhuyinbo (2023-03-08 18:58:02)
> >>
> >> =E5=9C=A8 2023/3/8 =E4=B8=8B=E5=8D=888:16, kernel test robot =E5=86=99=
=E9=81=93:
> >>> Hi Yinbo,
> >>>
> > [...]
> >>>
> >>>     drivers/clk/clk-loongson2.c: In function 'loongson2_calc_pll_rate=
':
> >>>>> drivers/clk/clk-loongson2.c:79:15: error: implicit declaration of f=
unction 'readq'; did you mean 'readl'? [-Werror=3Dimplicit-function-declara=
tion]
> >>>        79 |         val =3D readq(loongson2_pll_base + offset);
> >>>           |               ^~~~~
> >>>           |               readl
> >>>     cc1: some warnings being treated as errors
> >>
> >> The CONFIG_64BIT not enabled in your config file, I will add a depend =
on=20
> >> "CONFIG_64BIT" in my clock driver to fix this compile error.
> >=20
> > Do you need to use readq() here? Can you read two 32-bit registers with
> > readl() and put them together for a 64-bit number?
>=20
> If the platform supports 64-bit reads and these are actually one
> register, then readq makes sense - code is more readable, smaller, more
> efficient.
>=20

Please read the section in Documentation/driver-api/device-io.rst about
hi_lo_readq() and <linux/io-64-nonatomic-lo-hi.h>. We shouldn't need to
restrict the driver to CONFIG_64BIT. Instead, include one of these
header files to get the IO access primitives.