linux-kernel - Re: [PATCH] driver: bus: simple-pm-bus: Add Freescale i.MX8qm/qxp CSR compatible strings

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Date:   Thu, 26 Jan 2023 10:54:54 +0800
From:   Liu Ying <victor.liu@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        linux-imx@....com, Rob Herring <robh@...nel.org>,
        Lee Jones <lee@...nel.org>, krzysztof.kozlowski+dt@...aro.org,
        robh+dt@...nel.org
Subject: Re: [PATCH] driver: bus: simple-pm-bus: Add Freescale i.MX8qm/qxp
 CSR compatible strings

On Wed, 2023-01-25 at 10:05 +0100, Geert Uytterhoeven wrote:
> Hi Liu,

Hi Geert,

> 
> On Wed, Jan 25, 2023 at 9:31 AM Liu Ying <victor.liu@....com> wrote:
> > Freescale i.MX8qm/qxp CSR module matches with what the simple power
> > managed bus driver does, considering it needs an IPG clock to be
> > enabled before accessing it's child devices, the child devices need
> > to be populated by the CSR module and the child devices' power
> > management operations need to be propagated to their parent
> > devices.
> > Add the CSR module's compatible strings to simple_pm_bus_of_match[]
> > table to support the CSR module.
> > 
> > Suggested-by: Rob Herring <robh@...nel.org>
> > Suggested-by: Lee Jones <lee@...nel.org>
> > Signed-off-by: Liu Ying <victor.liu@....com>
> 
> Thanks for your patch!

Thanks for your review!

> 
> > ---
> > The CSR module's dt-binding documentation can be found at
> > Documentation/devicetree/bindings/mfd/fsl,imx8qxp-csr.yaml.
> > 
> > Suggested by Rob and Lee in this thread:
> > 
https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fproject%2Flinux-arm-kernel%2Fpatch%2F20221017075702.4182846-1-victor.liu%40nxp.com%2F&data=05%7C01%7Cvictor.liu%40nxp.com%7C3fa98ff270534078019508dafeb34b10%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C638102343312884116%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=zm8Z5gWt9yGXakYlxopUfZKLMUJRWTxq1kWHLyqhyww%3D&reserved=0
> > 
> >  drivers/bus/simple-pm-bus.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/bus/simple-pm-bus.c b/drivers/bus/simple-pm-
> > bus.c
> > index 7afe1947e1c0..4a7575afe6c6 100644
> > --- a/drivers/bus/simple-pm-bus.c
> > +++ b/drivers/bus/simple-pm-bus.c
> > @@ -120,6 +120,8 @@ static const struct of_device_id
> > simple_pm_bus_of_match[] = {
> >         { .compatible = "simple-mfd",   .data = ONLY_BUS },
> >         { .compatible = "isa",          .data = ONLY_BUS },
> >         { .compatible = "arm,amba-bus", .data = ONLY_BUS },
> > +       { .compatible = "fsl,imx8qm-lvds-csr", },
> > +       { .compatible = "fsl,imx8qxp-mipi-lvds-csr", },
> 
> I did read the thread linked above, and I still think you should just
> add "simple-pm-bus" to the compatible value in DTS, so no driver
> change
> is needed, cfr.
> Documentation/devicetree/bindings/bus/renesas,bsc.yaml.

This means that i.MX8qm/qxp CSR module dt-binding documentation needs
to be changed.  I'd like to know how Rob and Krzysztof think about
that.

> 
> If that doesn't work due to DT binding constraints, the latter should
> be fixed.

Adding "simple-pm-bus" to the compatible value in DTS doesn't work,
because "simple-mfd" is matched first and "ONLY_BUS" is set for
"simple-mfd".  s/simple-mfd/simple-pm-bus/ for the compatbile value in
DTS does work, but it means that fsl,imx8qxp-csr.yaml needs to be
changed and moved from mfd directory to bus directory...

Hmm, fsl,imx8qxp-csr.yaml was first written earlier than the below
patch.  Without that patch, child devices of the CSR module can be
populated.

98e96cf80045 ("drivers: bus: simple-pm-bus: Add support for probing
simple bus only devices")

Should I go ahead to fix fsl,imx8qxp-csr.yaml and move it to bus
directory?

Regards,
Liu Ying

> 
> >         { /* sentinel */ }
> >  };
> >  MODULE_DEVICE_TABLE(of, simple_pm_bus_of_match);
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- 
> geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a
> hacker. But
> when I'm talking to journalists I just say "programmer" or something
> like that.
>                                 -- Linus Torvalds