Message-ID: <b8801c83-f2dc-f144-de58-03e5c24436fd@linaro.org>
Date:   Mon, 20 Mar 2023 16:23:01 +0100
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Subject: Re: [EXT] Re: [PATCH v2 1/3] dt-bindings: usb: cdns-imx8qm: add
 imx8qm cdns3 glue bindings
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To:     Frank Li <frank.li@nxp.com>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>
Cc:     "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "festevam@gmail.com" <festevam@gmail.com>,
        "imx@lists.linux.dev" <imx@lists.linux.dev>,
        "kernel@pengutronix.de" <kernel@pengutronix.de>,
        "krzysztof.kozlowski+dt@linaro.org" 
        <krzysztof.kozlowski+dt@linaro.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        dl-linux-imx <linux-imx@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>,
        "s.hauer@pengutronix.de" <s.hauer@pengutronix.de>
References: <20230316212712.2426542-1-Frank.Li@nxp.com>
 <20230316212712.2426542-2-Frank.Li@nxp.com>
 <e6935c0c-375e-b763-ea91-3b8bbc906ebc@linaro.org>
 <AM6PR04MB4838D1958A029701E1601BA588BD9@AM6PR04MB4838.eurprd04.prod.outlook.com>
 <1fd1fe42-3da6-1598-a04d-cb99a9b4b145@linaro.org>
 <AM6PR04MB483800D7CDCC7AF48F88BF9688809@AM6PR04MB4838.eurprd04.prod.outlook.com>
From:   Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
In-Reply-To: <AM6PR04MB483800D7CDCC7AF48F88BF9688809@AM6PR04MB4838.eurprd04.prod.outlook.com>
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Precedence: bulk

On 20/03/2023 15:49, Frank Li wrote:
>>>>> +  clock-names:
>>>>> +    items:
>>>>> +      - const: usb3_lpm_clk
>>>>> +      - const: usb3_bus_clk
>>>>> +      - const: usb3_aclk
>>>>> +      - const: usb3_ipg_clk
>>>>> +      - const: usb3_core_pclk
>>>>> +
>>>>> +  assigned-clocks:
>>>>> +    items:
>>>>> +      - description: Phandle and clock specifier of IMX_SC_PM_CLK_PER.
>>>>> +      - description: Phandle and clock specifoer of
>> IMX_SC_PM_CLK_MISC.
>>>>> +      - description: Phandle and clock specifoer of
>>>> IMX_SC_PM_CLK_MST_BUS.
>>>>> +
>>>>> +  assigned-clock-rates:
>>>>> +    items:
>>>>> +      - description: Must be 125 Mhz.
>>>>> +      - description: Must be 12 Mhz.
>>>>> +      - description: Must be 250 Mhz.
>>>>
>>>> I would argue that both properties above are not needed. If your
>>>> hardware requires fixed frequencies, clock provider can fix them, can't it?
>>>
>>> Clock provider don't know fixed value and turn on only used by client.
>>
>> So maybe fix the clock provider? Or this device driver? Requiring by
>> binding specific frequencies for every board is a bit redundant.
> 
> It is not for every boards, it is common for a chip family.  Only a place to set for
> QM and QXP. 
> 
> The similar case is network driver, which require a specific frequency at clock assign.
> Generally frequency is fixed,  clock source name may change at difference chips. 

If frequency is always fixed, I don't understand why this is in DT
bindings. I would even say it should not be in DTS. We don't put into
DTS properties which are always the same, because otherwise they would
grow crazy big.

Best regards,
Krzysztof