linux-kernel - Re: [PATCH v7 5/6] arm64: dts: marvell: armada-37xx: add device node for UART clock and use it

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Date:   Wed, 13 Oct 2021 16:19:54 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Gregory CLEMENT <gregory.clement@...tlin.com>
Cc:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Vladimir Vid <vladimir.vid@...tura.hr>,
        Marek Behún <kabel@...nel.org>,
        linux-clk@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v7 5/6] arm64: dts: marvell: armada-37xx: add device node
 for UART clock and use it

On Wednesday 13 October 2021 16:13:16 Gregory CLEMENT wrote:
> Hello Pali,
> 
> > This change defines DT node for UART clock "marvell,armada-3700-uart-clock"
> > and use this UART clock as a base clock for all UART devices.
> >
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> >
> > ---
> > Changes in v6:
> > * Do not disable uartclk by default
> > * Rename node to clock-controller@...10
> > ---
> >  arch/arm64/boot/dts/marvell/armada-37xx.dtsi | 14 ++++++++++++--
> >  1 file changed, 12 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/boot/dts/marvell/armada-37xx.dtsi b/arch/arm64/boot/dts/marvell/armada-37xx.dtsi
> > index 9acc5d2b5a00..f9bfe73d8ec2 100644
> > --- a/arch/arm64/boot/dts/marvell/armada-37xx.dtsi
> > +++ b/arch/arm64/boot/dts/marvell/armada-37xx.dtsi
> > @@ -132,10 +132,20 @@
> >  				reg = <0x11500 0x40>;
> >  			};
> >  
> > +			uartclk: clock-controller@...10 {
> > +				compatible = "marvell,armada-3700-uart-clock";
> > +				reg = <0x12010 0x4>, <0x12210 0x4>;
> > +				clocks = <&tbg 0>, <&tbg 1>, <&tbg 2>,
> > +					<&tbg 3>, <&xtalclk>;
> > +				clock-names = "TBG-A-P", "TBG-B-P", "TBG-A-S",
> > +					"TBG-B-S", "xtal";
> > +				#clock-cells = <1>;
> > +			};
> > +
> >  			uart0: serial@...00 {
> >  				compatible = "marvell,armada-3700-uart";
> >  				reg = <0x12000 0x18>;
> > -				clocks = <&xtalclk>;
> > +				clocks = <&uartclk 0>;
> 
> What happens if we have a new kernel using on old device tree ?

Hello! There would be no change. New kernel would work as old kernel.
Into clocks property you can still set xtatclk as before and it would
still works.

> Gregory
> 
> >  				interrupts =
> >  				<GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>,
> >  				<GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
> > @@ -147,7 +157,7 @@
> >  			uart1: serial@...00 {
> >  				compatible = "marvell,armada-3700-uart-ext";
> >  				reg = <0x12200 0x30>;
> > -				clocks = <&xtalclk>;
> > +				clocks = <&uartclk 1>;
> >  				interrupts =
> >  				<GIC_SPI 30 IRQ_TYPE_EDGE_RISING>,
> >  				<GIC_SPI 31 IRQ_TYPE_EDGE_RISING>;
> > -- 
> > 2.20.1
> >
> 
> -- 
> Gregory Clement, Bootlin
> Embedded Linux and Kernel engineering
> http://bootlin.com