linux-kernel - Re: [PATCH] arm64: dts: imx8mq: Add clock parents for mipi dphy

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Message-ID: <20210110170321.GA30072@bogon.m.sigxcpu.org>
Date:   Sun, 10 Jan 2021 18:03:21 +0100
From:   Guido Günther <agx@...xcpu.org>
To:     Shawn Guo <shawnguo@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Peng Fan <peng.fan@....com>,
        Dong Aisheng <aisheng.dong@....com>,
        Anson Huang <Anson.Huang@....com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Shengjiu Wang <shengjiu.wang@....com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: imx8mq: Add clock parents for mipi dphy

Hi,
On Sun, Jan 10, 2021 at 08:46:29PM +0800, Shawn Guo wrote:
> On Fri, Dec 18, 2020 at 06:50:05PM +0100, Guido Günther wrote:
> > This makes sure the clock tree setup for the dphy is not dependent on
> > other components.
> > 
> > Without this change bringing up the display can fail like
> > 
> >   kernel: phy phy-30a00300.dphy.2: Invalid CM/CN/CO values: 165/217/1
> >   kernel: phy phy-30a00300.dphy.2: for hs_clk/ref_clk=451656000/593999998 ~ 165/217
> > 
> > if LCDIF doesn't set up that part of the clock tree first. This was
> > noticed when testing the Librem 5 devkit with defconfig. It doesn't
> > happen when modules are built in.
> > 
> > Signed-off-by: Guido Günther <agx@...xcpu.org>
> > ---
> >  arch/arm64/boot/dts/freescale/imx8mq.dtsi | 11 ++++++++---
> >  1 file changed, 8 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mq.dtsi b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > index a841a023e8e0..ca0847e8f13c 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > +++ b/arch/arm64/boot/dts/freescale/imx8mq.dtsi
> > @@ -1016,9 +1016,14 @@ dphy: dphy@...00300 {
> >  				reg = <0x30a00300 0x100>;
> >  				clocks = <&clk IMX8MQ_CLK_DSI_PHY_REF>;
> >  				clock-names = "phy_ref";
> > -				assigned-clocks = <&clk IMX8MQ_CLK_DSI_PHY_REF>;
> > -				assigned-clock-parents = <&clk IMX8MQ_VIDEO_PLL1_OUT>;
> > -				assigned-clock-rates = <24000000>;
> > +				assigned-clocks = <&clk IMX8MQ_VIDEO_PLL1_REF_SEL>,
> > +						  <&clk IMX8MQ_VIDEO_PLL1_BYPASS>,
> > +						  <&clk IMX8MQ_CLK_DSI_PHY_REF>,
> > +						  <&clk IMX8MQ_VIDEO_PLL1>;
> 
> You do not seem to set parent or rate on IMX8MQ_VIDEO_PLL1.  Why do you
> have it here?

Good point. I've added a clock rate for IMX8MQ_VIDEO_PLL1 since
then the clock tree reproduces exactly with and with the DSI host
controller disabled in DT (otherwise we end up with a rate of 22MHz
instead of 24Mhz).

Cheers,
 -- Guido

> 
> Shawn
> 
> > +				assigned-clock-parents = <&clk IMX8MQ_CLK_25M>,
> > +						  <&clk IMX8MQ_VIDEO_PLL1>,
> > +						  <&clk IMX8MQ_VIDEO_PLL1_OUT>;
> > +				assigned-clock-rates = <0>, <0>, <24000000>;
> >  				#phy-cells = <0>;
> >  				power-domains = <&pgc_mipi>;
> >  				status = "disabled";
> > -- 
> > 2.29.2
> > 
>