linux-kernel - Re: [PATCH 4/5] ARM: dts: imxrt1050: remove mmc max-frequency property

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Date:   Tue, 18 Oct 2022 19:29:27 +0200
From:   Giulio Benetti <giulio.benetti@...ettiengineering.com>
To:     Bough Chen <haibo.chen@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>
Cc:     Stephen Boyd <sboyd@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH 4/5] ARM: dts: imxrt1050: remove mmc max-frequency
 property

Hi Haibo,

On 18/10/22 05:01, Bough Chen wrote:
>> -----Original Message-----
>> From: Giulio Benetti <giulio.benetti@...ettiengineering.com>
>> Sent: 2022年10月18日 7:56
>> To: devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
>> linux-kernel@...r.kernel.org; linux-clk@...r.kernel.org;
>> linux-mmc@...r.kernel.org
>> Cc: Stephen Boyd <sboyd@...nel.org>; Bough Chen <haibo.chen@....com>;
>> Adrian Hunter <adrian.hunter@...el.com>; Ulf Hansson
>> <ulf.hansson@...aro.org>; Giulio Benetti
>> <giulio.benetti@...ettiengineering.com>
>> Subject: [PATCH 4/5] ARM: dts: imxrt1050: remove mmc max-frequency
>> property
>>
>> According to i.MXRT1050 Reference Manual usdhc supports up to 208Mhz clock
> 
> Please double check this. As I know, the i.MXRT1050 and i.MX6/7/8/9 series use the same usdhc IP, maybe include some small difference.
> For the usdhc in i.MX6/7/8/9, I confirmed with IC team, the card clock output from usdhc can't be upper than 
200MHz, otherwise maybe meet some stable related issue.

Thanks for poiting, I've double checked and you're right. RM states 
208Mhz but DS states 200Mhz and it makes sense because of HS200.

> So here I think should change to like this:
>   max-frequency = <200000000>;

Ok, I'll send a V2 for this. I wait for other comments on the other 
patches for a bit before.

Best regards
-- 
Giulio Benetti
CEO/CTO@...etti Engineering sas

> 
> Best Regards
> Haibo Chen
> 
> 
>> so let's remove max-frequency property in the .dtsi base file and in case add
>> that property in the board specific .dts file for a specific device connected to it.
>>
>> Signed-off-by: Giulio Benetti <giulio.benetti@...ettiengineering.com>
>> ---
>>   arch/arm/boot/dts/imxrt1050.dtsi | 1 -
>>   1 file changed, 1 deletion(-)
>>
>> diff --git a/arch/arm/boot/dts/imxrt1050.dtsi
>> b/arch/arm/boot/dts/imxrt1050.dtsi
>> index 114465e4dde6..0b44cc4ce6ad 100644
>> --- a/arch/arm/boot/dts/imxrt1050.dtsi
>> +++ b/arch/arm/boot/dts/imxrt1050.dtsi
>> @@ -93,7 +93,6 @@ usdhc1: mmc@...c0000 {
>>   			bus-width = <4>;
>>   			fsl,wp-controller;
>>   			no-1-8-v;
>> -			max-frequency = <4000000>;
>>   			fsl,tuning-start-tap = <20>;
>>   			fsl,tuning-step = <2>;
>>   			status = "disabled";
>> --
>> 2.34.1
>