Message-ID: <6ff60914-0c39-9916-2e3a-a906b4cdef0d@kernel.org>
Date:   Tue, 14 Mar 2023 07:49:40 +0100
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Subject: Re: [PATCH v13 2/2] clk: clk-loongson2: add clock controller driver
 support
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To:     Stephen Boyd <sboyd@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>
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
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>
 <61eee19400e9a45ce9543bfd92a27eaa.sboyd@kernel.org>
From:   Krzysztof Kozlowski <krzk@kernel.org>
In-Reply-To: <61eee19400e9a45ce9543bfd92a27eaa.sboyd@kernel.org>
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On 13/03/2023 19:20, Stephen Boyd wrote:
>>>> The CONFIG_64BIT not enabled in your config file, I will add a depend on 
>>>> "CONFIG_64BIT" in my clock driver to fix this compile error.
>>>
>>> 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?
>>
>> If the platform supports 64-bit reads and these are actually one
>> register, then readq makes sense - code is more readable, smaller, more
>> efficient.
>>
> 
> 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.

These primitives are for 32bit access. Quoting: "on 32-bit
architectures". What's the point of them if the code *will never* run on
32-bit? It will be a fake choice of linux/io-64-nonatomic-lo-hi.h or
linux/io-64-nonatomic-hi-lo.h misleading users to think this was tested
on 32-bit.

Best regards,
Krzysztof