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

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Date:   Fri, 06 Nov 2020 15:04:08 +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 09:11, schrieb Michael Walle:
> 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.

Btw on the LS1028A this should be "<&clockgen 2 0>;" Will be fixed in 
the
new version.
And because there so much difference between LS1028A and LX2160A, I'll 
mark
the last patch (this one, for the LX2160A) as RFC until someone will 
test it.

-michael