linux-kernel - Re: [PATCH] arm64: dts: imx8mp: drop dmas property for uart console

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Date:   Sat, 25 Jun 2022 00:15:51 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Sascha Hauer <s.hauer@...gutronix.de>
Cc:     "Peng Fan (OSS)" <peng.fan@....nxp.com>, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, shawnguo@...nel.org,
        festevam@...il.com, linux-imx@....com, hvilleneuve@...onoff.com,
        l.stach@...gutronix.de, abbaraju.manojsai@...rulasolutions.com,
        jagan@...rulasolutions.com, matteo.lisi@...icam.com,
        tharvey@...eworks.com, t.remmet@...tec.de,
        u.kleine-koenig@...gutronix.de, t.remmet@...tec.deh,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Peng Fan <peng.fan@....com>
Subject: Re: [PATCH] arm64: dts: imx8mp: drop dmas property for uart console

On Wed, Jun 22, 2022 at 12:24 AM Sascha Hauer <s.hauer@...gutronix.de> wrote:
>
> +Cc Saravana Kannan <saravanak@...gle.com>, the author of 71066545b48e4
>
> On Wed, Jun 22, 2022 at 02:20:27PM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan@....com>
> >
> > Commit 71066545b48e4("driver core: Set fw_devlink.strict=1 by default")
> > default set fw_devlink to true. This has a side effect to i.MX uart
> > console. The sdma will make the i.MX8MP uart driver defer probe for some
> > time (~10s with i.MX8MP-EVK board) until sdma ready, because sdma is a
> > supplier with property dmas set in device tree node.
>
> I just tested this on an i.MX6 board and observed the same behaviour.
> The same will happen on any other i.MX board as well. This will also
> likely happen on any other SoC on which the UART driver uses dmaengine.
>
> >
> > Since this uart is for console, we need log printed out as soon as
> > possible, so remove the dmas property for the uart console node.
>
> Fixing this at board level is not really an option because that means
> fixing each and every, at least i.MX board in the tree. Furthermore
> this would mean to bring the deleted property back in and to remove
> another dmas property should a user want to switch to another console
> port.
>
> For what it's worth: NACK for 71066545b48e4.

Hi Peng/Sascha/Fabio,

I was looking at a fix for this (even when stdout-path isn't set in
DT) and looking at the older code (say, 5.18), and it looks like
before my recent changes the console would still only get probed
during late_initcall(). Does that match your experience?

Thanks,
Saravana

>
> Sascha
>
> >
> > Signed-off-by: Peng Fan <peng.fan@....com>
> > ---
> >
> > V1:
> >  The upper set fw_devlink.strict=1 patch is in linux-next tree.
> >
> >  arch/arm64/boot/dts/freescale/imx8mp-evk.dts                  | 2 ++
> >  arch/arm64/boot/dts/freescale/imx8mp-icore-mx8mp-edimm2.2.dts | 2 ++
> >  arch/arm64/boot/dts/freescale/imx8mp-phyboard-pollux-rdk.dts  | 2 ++
> >  arch/arm64/boot/dts/freescale/imx8mp-venice-gw74xx.dts        | 2 ++
> >  4 files changed, 8 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mp-evk.dts b/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
> > index fb11c03bc8b1..3fdb38bc0069 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
> > +++ b/arch/arm64/boot/dts/freescale/imx8mp-evk.dts
> > @@ -359,6 +359,8 @@ &uart2 {
> >       pinctrl-names = "default";
> >       pinctrl-0 = <&pinctrl_uart2>;
> >       status = "okay";
> > +     /delete-property/ dmas;
> > +     /delete-property/ dma-names;
> >  };
> >
> >  &usb3_phy1 {
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mp-icore-mx8mp-edimm2.2.dts b/arch/arm64/boot/dts/freescale/imx8mp-icore-mx8mp-edimm2.2.dts
> > index dd703b6a5e17..fb2b44e94482 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mp-icore-mx8mp-edimm2.2.dts
> > +++ b/arch/arm64/boot/dts/freescale/imx8mp-icore-mx8mp-edimm2.2.dts
> > @@ -69,6 +69,8 @@ &uart2 {
> >       pinctrl-names = "default";
> >       pinctrl-0 = <&pinctrl_uart2>;
> >       status = "okay";
> > +     /delete-property/ dmas;
> > +     /delete-property/ dma-names;
> >  };
> >
> >  &usb3_phy0 {
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mp-phyboard-pollux-rdk.dts b/arch/arm64/boot/dts/freescale/imx8mp-phyboard-pollux-rdk.dts
> > index 6aa720bafe28..68a478151292 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mp-phyboard-pollux-rdk.dts
> > +++ b/arch/arm64/boot/dts/freescale/imx8mp-phyboard-pollux-rdk.dts
> > @@ -99,6 +99,8 @@ &uart1 {
> >       pinctrl-names = "default";
> >       pinctrl-0 = <&pinctrl_uart1>;
> >       status = "okay";
> > +     /delete-property/ dmas;
> > +     /delete-property/ dma-names;
> >  };
> >
> >  /* SD-Card */
> > diff --git a/arch/arm64/boot/dts/freescale/imx8mp-venice-gw74xx.dts b/arch/arm64/boot/dts/freescale/imx8mp-venice-gw74xx.dts
> > index 521215520a0f..f90c1ac2791c 100644
> > --- a/arch/arm64/boot/dts/freescale/imx8mp-venice-gw74xx.dts
> > +++ b/arch/arm64/boot/dts/freescale/imx8mp-venice-gw74xx.dts
> > @@ -554,6 +554,8 @@ &uart2 {
> >       pinctrl-names = "default";
> >       pinctrl-0 = <&pinctrl_uart2>;
> >       status = "okay";
> > +     /delete-property/ dmas;
> > +     /delete-property/ dma-names;
> >  };
> >
> >  &uart4 {
> > --
> > 2.25.1
> >
> >
>
> --
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