Re: (EXT) Re: [PATCH v2 1/1] arm64: dts: imx8qm: Add fsl, imx7ulp-lpuart compatible to lpuart

[Shawn Guo <shawnguo@kernel.org>]

On Mon, Nov 22, 2021 at 08:38:28AM +0100, Alexander Stein wrote:
> Am Montag, dem 22.11.2021 um 09:43 +0800 schrieb Shawn Guo:
> > On Tue, Nov 16, 2021 at 01:58:14PM +0100, Alexander Stein wrote:
> > > After commit b4b844930f27 ("tty: serial: fsl_lpuart: drop earlycon
> > > entry
> > > for i.MX8QXP") earlycon support was essentially removed from
> > > imx8qm/imx8qxp due to missing compatible.
> > > The commit message says "i.MX8QXP lpuart is compatible with
> > > i.MX7ULP" so
> > > adding a fallback compatible should be fine.
> > > With this change earlycon is supported again on imx8qm/imx8qxp.
> > > 
> > > Signed-off-by: Alexander Stein <
> > > alexander.stein@ew.tq-group.com
> > > >
> > > Reviewed-by: Peng Fan <
> > > peng.fan@nxp.com
> > > >
> > > ---
> > > Changes in v2:
> > > * Fix typo in commit message: 'early' -> 'earlycon'
> > > 
> > >  arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi | 8 ++++----
> > >  1 file changed, 4 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi
> > > b/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi
> > > index bbe5f5ecfb92..3486b99ab6eb 100644
> > > --- a/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi
> > > +++ b/arch/arm64/boot/dts/freescale/imx8qm-ss-dma.dtsi
> > > @@ -19,19 +19,19 @@ uart4_lpcg: clock-controller@5a4a0000 {
> > >  };
> > >  
> > >  &lpuart0 {
> > > -	compatible = "fsl,imx8qm-lpuart", "fsl,imx8qxp-lpuart";
> > > +	compatible = "fsl,imx8qm-lpuart", "fsl,imx8qxp-lpuart",
> > > "fsl,imx7ulp-lpuart";
> > 
> > Then fsl,imx8qxp-lpuart should be dropped?
> 
> If you drop fsl,imx8qxp-lpuart in the compatible list, fsl_lpuart.c
> needs a new lpuart_soc_data for imx8qm in order to work. "fsl,imx7ulp-
> lpuart" is not enough for imx8qm, as (among other things) "baud" clk is
> mising in imx7. IMHO there are 2 ways:
> 
> 1st
> Add both fsl,imx8qxp-lpuart and fsl,imx7ulp-lpuart to the compatible
> list to get both regular serial support (fsl,imx8qxp-lpuart) as well as
> earlycon (fsl,imx7ulp-lpuart). In this case the bindings need to get
> fixed as well, see [1]
> 
> 2nd
> Remove fsl,imx8qxp-lpuart compatible for imx8qm. But in this case
> everything done for imx8qxp in fsl_lpuart.c has to be duplicated.
> fsl,imx7ulp-lpuart is still required for earlycon support.
> 
> If you want to get rid of fsl,imx7ulp-lpuart compatible for
> imx8qm/imx8qxp in either case, you need to revert b4b844930f27 ("tty:
> serial: fsl_lpuart: drop earlycon entry for i.MX8QXP").

It looks to me that commit b4b844930f27 caused a regression for imx8qm,
so should be reverted.

Shawn

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