linux-kernel - Re: [PATCH 02/14] dt-bindings: phy: qcom,qmp-usb3-dp: fix sc8280xp bindings

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Message-ID: <bcc327b6-c38b-86a9-34cb-440ad33df210@linaro.org>
Date:   Mon, 14 Nov 2022 19:14:48 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Johan Hovold <johan@...nel.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Vinod Koul <vkoul@...nel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/14] dt-bindings: phy: qcom,qmp-usb3-dp: fix sc8280xp
 bindings

On 14/11/2022 18:38, Johan Hovold wrote:
> On Mon, Nov 14, 2022 at 06:19:25PM +0300, Dmitry Baryshkov wrote:
>> On 14/11/2022 17:18, Johan Hovold wrote:
>>> On Mon, Nov 14, 2022 at 03:07:41PM +0100, Krzysztof Kozlowski wrote:
>>>> On 14/11/2022 14:27, Johan Hovold wrote:
>>>>> On Fri, Nov 11, 2022 at 04:17:29PM +0100, Krzysztof Kozlowski wrote:
>>>>>> On 11/11/2022 10:24, Johan Hovold wrote:
> 
>>>>> I noticed that several bindings leave the clock indexes unspecified, or
>>>>> have header files defining some or all of them. I first added a QMP
>>>>> header but that seemed like overkill, especially if we'd end up with
>>>>> one header per SoC (cf. the GCC headers) due to (known and potential)
>>>>> platform differences.
> 
>>>>> Shall I add back a shared header for all PHYs handled by this driver
>>>>> (another implementation detail) even if this could eventually lead to
>>>>> describing clocks not supported by a particular SoC (so such constraints
>>>>> would still need to be described by the binding somehow):
>>>>>
>>>>> 	/* QMP clocks */
>>>>> 	#define QMP_USB3_PIPE_CLK	0
>>>>> 	#define QMP_DP_LINK_CLK		1
>>>>> 	#define QMP_DP_VCO_DIV_CLK	2
>>
>> Maybe QMP_COMBO_USB3_PIPE_CLK, QMP_COMBO_DP_LINK_CLK,
>> QMP_COMBO_DP_VCO_DIV_CLK?
> 
> "COMBO" is just the name of the Linux driver and does not belong in the
> binding.

We do not have any standard (iow, coming from the docs) name, so we can 
invent it on our own.

>   
>> I'll then extend this header with QMP_UFS_RX_SYMBOL_0_CLK
>> QMP_UFS_RX_SYMBOL_1_CLK and QMP_UFS_TX_SYMBOL_0_CLK.
> 
> Yeah, I had those in mind when creating the header and using a generic
> QMP prefix (even if I didn't end up using the header in v1).
> 
> This could just be mapping of (arbitrary) QMP indexes to clocks and we
> use it for USB3, DP, UFS and later also USB4.
> 
> This will however mean that the indexes are not necessarily zero-based
> and consecutive for a specific SoC and PHY. But that's perhaps a
> non-issue (cf. the PHY_TYPE defines).

Ugh. Please, no. We have symbol clocks for UFS PHY, USB+DP clocks for 
USB+DP PHY, but let's not go for the unified clocks index definition.

> 
> We'd still need to describe which clocks are available on a particular
> SoC and PHY, and that's partly why I used 'clock-output-names' to fix
> the mapping in the binding. Guess we can just list the valid defines in
> the property description as I did for #phy-cells.
> 
> Johan

-- 
With best wishes
Dmitry