linux-kernel - Re: [PATCH v9 3/4] clk: meson: add DT documentation for emmc clock controller

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Date:   Mon, 17 Jan 2022 10:43:01 +0800
From:   Liang Yang <liang.yang@...ogic.com>
To:     Stephen Boyd <sboyd@...nel.org>,
        Jerome Brunet <jbrunet@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Rob Herring <robh+dt@...nel.org>, <linux-clk@...r.kernel.org>
CC:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Jianxin Pan <jianxin.pan@...ogic.com>,
        Victor Wan <victor.wan@...ogic.com>,
        XianWei Zhao <xianwei.zhao@...ogic.com>,
        Kelvin Zhang <kelvin.zhang@...ogic.com>,
        BiChao Zheng <bichao.zheng@...ogic.com>,
        YongHui Yu <yonghui.yu@...ogic.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-amlogic@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v9 3/4] clk: meson: add DT documentation for emmc clock
 controller



On 2022/1/15 6:59, Stephen Boyd wrote:
> [ EXTERNAL EMAIL ]
> 
> Quoting Liang Yang (2022-01-13 19:06:07)
>> Hi Stephen,
>>
>> Thanks for your quick response.
>>
>> On 2022/1/14 5:29, Stephen Boyd wrote:
>>> [ EXTERNAL EMAIL ]
>>>
>>> Quoting Liang Yang (2022-01-13 03:57:44)
>>>> Document the MMC sub clock controller driver, the potential consumer
>>>> of this driver is MMC or NAND. Also add four clock bindings IDs which
>>>> provided by this driver.
>>>>
>>>> Signed-off-by: Liang Yang <liang.yang@...ogic.com>
>>>> ---
>>>>    .../bindings/clock/amlogic,mmc-clkc.yaml      | 64 +++++++++++++++++++
>>>>    include/dt-bindings/clock/amlogic,mmc-clkc.h  | 14 ++++
>>>>    2 files changed, 78 insertions(+)
>>>>    create mode 100644 Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.yaml
>>>>    create mode 100644 include/dt-bindings/clock/amlogic,mmc-clkc.h
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.yaml b/Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.yaml
>>>> new file mode 100644
>>>> index 000000000000..a274c3d5fc2e
>>>> --- /dev/null
>>>> +++ b/Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.yaml
>>>> @@ -0,0 +1,64 @@
>>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>>> +%YAML 1.2
>>>> +---
>>>> +$id: http://devicetree.org/schemas/clock/amlogic,mmc-clkc.yaml#
>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>>>> +
>>>> +title: Amlogic MMC Sub Clock Controller Driver Device Tree Bindings
>>>> +
>>>> +maintainers:
>>>> +  - jianxin.pan@...ogic.com
>>>> +  - liang.yang@...ogic.com
>>>> +
>>>> +properties:
>>>> +  compatible:
>>>> +    enum:
>>>> +      - "amlogic,axg-mmc-clkc", "syscon"
>>>
>>> Why is it a syscon?
>>
>> The register documented by reg is shared with SD/eMMC controller port C,
>> and it need to be ops on NFC driver.
>>
> 
> Is this the case where the clk is inside the SD/eMMC controller? Can the
yes.
> mmc driver register the clk controller from there and pass it an iomem
> pointer to poke clks?
we can't do that since EMMC and NAND is mutually exclusivem. both of 
them share the same data pins.
> 
> .