Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <bc5458fe-083c-d679-9fcb-95810a290da8@linaro.org>
Date:   Sun, 19 Jun 2022 14:05:30 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.10.0
Subject: Re: [PATCH 2/3] dt-bindings: usb: mtk-xhci: Allow middle optional
 clocks to be missing
Content-Language: en-US
To:     Chunfeng Yun <chunfeng.yun@mediatek.com>,
        =?UTF-8?B?TsOtY29sYXMgRi4gUi4gQS4gUHJhZG8=?= 
        <nfraprado@collabora.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Matthias Brugger <matthias.bgg@gmail.com>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>, kernel@collabora.com,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mediatek@lists.infradead.org, linux-usb@vger.kernel.org
References: <20220617222916.2435618-1-nfraprado@collabora.com>
 <20220617222916.2435618-3-nfraprado@collabora.com>
 <8639e64d-c659-7090-2d0a-078fd96cfbd4@linaro.org>
 <bb460aa483cc888ffa36709d9e9c1f2e3be0e000.camel@mediatek.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <bb460aa483cc888ffa36709d9e9c1f2e3be0e000.camel@mediatek.com>
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 19/06/2022 09:46, Chunfeng Yun wrote:
> On Fri, 2022-06-17 at 18:25 -0700, Krzysztof Kozlowski wrote:
>> On 17/06/2022 15:29, Nícolas F. R. A. Prado wrote:
>>> The current clock list in the binding doesn't allow for one of the
>>> optional clocks to be missing and a subsequent clock to be present.
>>> An
>>> example where this is an issue is in mt8192.dtsi, which has
>>> "sys_ck",
>>> "ref_ck", "xhci_ck" and would cause dtbs_check warnings.
>>>
>>> Change the clock list in a way that allows the middle optional
>>> clocks to
>>> be missing, while still guaranteeing a fixed order. The "ref_ck" is
>>> kept
>>> as a const even though it is optional for simplicity, since it is
>>> present in all current dts files.
>>>
>>> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
>>> ---
>>>
>>>  .../devicetree/bindings/usb/mediatek,mtk-xhci.yaml       | 9
>>> +++++++--
>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtk-
>>> xhci.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtk-
>>> xhci.yaml
>>> index 63cbc2b62d18..99a1b233ec90 100644
>>> --- a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
>>> +++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
>>> @@ -80,8 +80,13 @@ properties:
>>>      items:
>>>        - const: sys_ck  # required, the following ones are optional
>>>        - const: ref_ck
>>> -      - const: mcu_ck
>>> -      - const: dma_ck
>>> +      - enum:
>>> +          - mcu_ck
>>> +          - dma_ck
>>> +          - xhci_ck
>>> +      - enum:
>>> +          - dma_ck
>>> +          - xhci_ck
>>>        - const: xhci_ck
>>
>> You allow now almost any order here, including incorrect like
>> sys,ref,xhci,xhci,xhci.
>>
>> The order of clocks has to be fixed and we cannot allow flexibility.
>> Are
>> you sure that these clocks are actually optional (not wired to the
>> device)?
> In fact, these optional clocks are fixed, due to no gates are provided,
> SW can't control them by CCF;
> In this case, I usually use a fixed clock, or ignore it.

But in some versions these clocks are controllable or not?

Best regards,
Krzysztof