linux-kernel - Re: [PATCH] arm64: dts: imx8mp: use correct clock for eqos timestamping counter

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Date:   Wed, 19 Jul 2023 16:12:29 +0200
From:   Johannes Zink <j.zink@...gutronix.de>
To:     Fabio Estevam <festevam@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        patchwork-jzi@...gutronix.de, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: imx8mp: use correct clock for eqos
 timestamping counter

Hi Fabio,

On 7/19/23 16:03, Fabio Estevam wrote:
> Hi Johannes,
> 
> On Wed, Jul 19, 2023 at 10:59 AM Johannes Zink <j.zink@...gutronix.de> wrote:
>>
>> The i.MX8MP Reference Manual rev 1 06/2021, section 11.7.2.5 "Timestamp
>> Support" indicates the PTP timestamp clock expects a typical frequency
>> of 125MHz.
>>
>> As this also improves the precision of the measured timestamps: assign
>> appropriate 125MHz Clock parent. As no one except the timestamping
>> counter uses this clock, there are no side-effects of this change in
>> other peripherals.
>>
>> Signed-off-by: Johannes Zink <j.zink@...gutronix.de>
>> ---
>>   arch/arm64/boot/dts/freescale/imx8mp.dtsi | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/boot/dts/freescale/imx8mp.dtsi b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
>> index 6f2f50e1639c..7f80dff914c2 100644
>> --- a/arch/arm64/boot/dts/freescale/imx8mp.dtsi
>> +++ b/arch/arm64/boot/dts/freescale/imx8mp.dtsi
>> @@ -1334,7 +1334,7 @@ eqos: ethernet@...f0000 {
>>                                                    <&clk IMX8MP_CLK_ENET_QOS_TIMER>,
>>                                                    <&clk IMX8MP_CLK_ENET_QOS>;
>>                                  assigned-clock-parents = <&clk IMX8MP_SYS_PLL1_266M>,
>> -                                                        <&clk IMX8MP_SYS_PLL2_100M>,
>> +                                                        <&clk IMX8MP_SYS_PLL2_125M>,
>>                                                           <&clk IMX8MP_SYS_PLL2_125M>;
>>                                  assigned-clock-rates = <0>, <100000000>, <125000000>;
> 
> Shouldn't this also be changed to:
> 
> assigned-clock-rates = <0>, <125000000>, <125000000>;
> 

good catch, thanks! Gonna fix it in v2.

Best regards
Johannes

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