linux-kernel - Re: [PATCH v2 5/5] arm64: dts: lx2160a: fix FlexSPI clock

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Message-ID: <639fa8e62e0b98bedf4077f76fd75e83@walle.cc>
Date:   Fri, 06 Nov 2020 09:11:15 +0100
From:   Michael Walle <michael@...le.cc>
To:     Leo Li <leoyang.li@....com>
Cc:     linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>
Subject: Re: [PATCH v2 5/5] arm64: dts: lx2160a: fix FlexSPI clock

Am 2020-11-06 03:00, schrieb Leo Li:
>> -----Original Message-----
>> From: Michael Walle <michael@...le.cc>
>> Sent: Thursday, November 5, 2020 1:35 PM
>> To: linux-clk@...r.kernel.org; devicetree@...r.kernel.org; linux-
>> kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org
>> Cc: Michael Turquette <mturquette@...libre.com>; Stephen Boyd
>> <sboyd@...nel.org>; Rob Herring <robh+dt@...nel.org>; Shawn Guo
>> <shawnguo@...nel.org>; Leo Li <leoyang.li@....com>; Michael Walle
>> <michael@...le.cc>
>> Subject: [PATCH v2 5/5] arm64: dts: lx2160a: fix FlexSPI clock
>> 
>> Now that we have a proper driver for the FlexSPI interface use it. 
>> This will fix
>> SCK frequency switching on Layerscape SoCs.
>> 
>> This was only compile time tested.
>> 
>> Signed-off-by: Michael Walle <michael@...le.cc>
>> ---
>> Changes since v1:
>>  - none
>> 
>>  arch/arm64/boot/dts/freescale/fsl-lx2160a.dtsi | 15 +++++++++++++--
>>  1 file changed, 13 insertions(+), 2 deletions(-)
>> 
>> diff --git a/arch/arm64/boot/dts/freescale/fsl-lx2160a.dtsi
>> b/arch/arm64/boot/dts/freescale/fsl-lx2160a.dtsi
>> index 83072da6f6c6..6e375e80bd35 100644
>> --- a/arch/arm64/boot/dts/freescale/fsl-lx2160a.dtsi
>> +++ b/arch/arm64/boot/dts/freescale/fsl-lx2160a.dtsi
>> @@ -659,9 +659,20 @@
>>  		};
>> 
>>  		dcfg: syscon@...0000 {
>> -			compatible = "fsl,lx2160a-dcfg", "syscon";
>> +			#address-cells = <1>;
>> +			#size-cells = <1>;
>> +			compatible = "fsl,lx2160a-dcfg", "syscon", "simple-
>> mfd";
>>  			reg = <0x0 0x1e00000 0x0 0x10000>;
>> +			ranges = <0x0 0x0 0x1e00000 0x10000>;
>>  			little-endian;
>> +
>> +			fspi_clk: clock-controller@900 {
>> +				compatible = "fsl,lx2160a-flexspi-clk";
>> +				reg = <0x900 0x4>;
>> +				#clock-cells = <0>;
>> +				clocks = <&clockgen 4 0>;
> 
> This is different from the current <&clockgen 4 3>, is it an intended 
> change?

Yes, this change was intended. At least on the LS1028A this clock 
divider is
connected to the platform base clock. I don't know why there was
"<&clockgen 4 3>" in the first place. But because the clkgen clock 
cannot
be changed it didn't matter before this commit. The flexspi driver only
calls clk_set_rate(), never clk_get_rate(). On the LS1028A I actually
meassured the resulting SCK frequency.
Looking at Figure 7. (Clock subsystem block diagram) in the LX2160A RM, 
this
seems to be the case here, too.

-michael