Subject: Re: [PATCH] arm64: dts: imx8mn: Fix duplicate node name

From: Krzysztof Kozlowski <[email-masked]>
Date: Tue, 8 Dec 2020 10:06:01 +0100

On Tue, Dec 08, 2020 at 08:57:49AM +0000, S.j. Wang wrote:
> > On Tue, Dec 08, 2020 at 08:44:51AM +0000, S.j. Wang wrote:
> > > > > > >
> > > > > > > On Mon, Dec 07, 2020 at 02:21:40PM +0100, Krzysztof Kozlowski
> > wrote:
> > > > > > > > On Mon, Dec 07, 2020 at 02:53:24PM +0800, Shengjiu Wang wrote:
> > > > > > > > > Error log:
> > > > > > > > > sysfs: cannot create duplicate filename
> > > > > > > '/bus/platform/devices/30000000.bus'
> > > > > > > > >
> > > > > > > > > The spba bus name is duplicate with aips bus name.
> > > > > > > > > Refine spba bus name to fix this issue.
> > > > > > > > >
> > > > > > > > > Fixes: 970406eaef3a ("arm64: dts: imx8mn: Enable
> > > > > > > > > Asynchronous Sample Rate Converter")
> > > > > > > > > Signed-off-by: Shengjiu Wang <[email-masked]>
> > > > > > > > > ---
> > > > > > > > >  arch/arm64/boot/dts/freescale/imx8mn.dtsi | 2 +-
> > > > > > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > > > > > >
> > > > > > > > > diff --git a/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> > > > > > > > > b/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> > > > > > > > > index fd669c0f3fe5..30762eb4f0a7 100644
> > > > > > > > > --- a/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> > > > > > > > > +++ b/arch/arm64/boot/dts/freescale/imx8mn.dtsi
> > > > > > > > > @@ -246,7 +246,7 @@ aips1: bus@30000000 {
> > > > > > > > >                     #size-cells = <1>;
> > > > > > > > >                     ranges;
> > > > > > > > >
> > > > > > > > > -                   spba: bus@30000000 {
> > > > > > > > > +                   spba: spba-bus@30000000 {
> > > > > > > >
> > > > > > > > The proper node name is "bus" so basically you introduce
> > > > > > > > wrong name to other problem.  Introducing wrong names at
> > > > > > > > least requires a
> > > > comment.
> > > > > > >
> > > > > > > I just noticed that my message was barely understandable... so
> > > > > > > let me
> > > > fix it:
> > > > > > >
> > > > > > > The proper node name is "bus" so basically you introduce wrong
> > > > > > > name to _fix_ other problem.  Introducing wrong names at least
> > > > requires a comment.
> > > > > > >
> > > > > > > > However the actual problem here is not in node names but in
> > > > addresses:
> > > > > > > >
> > > > > > > >       aips1: bus@30000000 {
> > > > > > > >               spba: bus@30000000 {
> > > > > > > >
> > > > > > > > You have to devices with the same unit address. How do you
> > > > > > > > share the address space?
> > > > > > > >
> > > > > > > > I think this should be rather fixed.
> > > > > > >
> > > > > > > And again, hungry keyboard ate a letter, so:
> > > > > > >
> > > > > > > You have _two_ devices with the same unit address. How do you
> > > > > > > share the address space?
> > > > > > > I think this should be rather fixed.
> > > > > > >
> > > > > >
> > > > > > spba is the first block of aips1 space, so it has same start
> > > > > > address as aips1.
> > > > >
> > > > > The reference manual describes it "Reserved for SDMA2 internal
> > > > > memory", so indeed it is first address but does it have to be mapped?
> > > > > Anyway, why don't you use ranges to remove the conflict?
> > > >
> > > > The IO address space remapping could be a solution but there is
> > > > another problem - the hardware representation in DT does not match
> > > > what reference manual is saying.
> > > >
> > > > The AIPS bus @30000000 has several IPs:
> > > >  - SAI2@30020000
> > > >  - ...
> > > >  - GPIO1@30200000
> > > >
> > > > However in DTS you will find additional SPBA bus for 30000000 -
> > 300c0000.
> > > > It's not really the SDMA, as SDMA is at different address. It is
> > > > rather an address space which SDMA should map... but it is not a bus
> > with children.
> > > > Adding spba-bus@30000000 with its children does not look like
> > > > correct representation of HW in DTS.
> > > >
> > >
> > > In the RM, it says AIPS-1 (s_b_1, via SPBA) Glob. Module Enable.
> > > Range is (30000000 - 300FFFFF)
> > 
> > No, AIPS-1 is till 303F_FFFF.
> 
> Yes,  AIPSA-1 is till 303F_FFFF,  but it is divided to 2 parts.
> (30000000 - 300FFFFF) is the first part. 
> 
> Please go to table 2-3 AIPS1 memory map in RM.  In the "region" column,
> There is " AIPS-1 (s_b_1, via SPBA) Glob. Module Enable". It means
> This part is connect to SPBA bus.

Thanks, I see it now. Indeed you have two buses which start at the same
address space. You can:
1. Remap addresses,
2. Rename APIS and SPBA to bus-1 and bus-2,
3. Add specific (non-generic) name to spba-bus which you did initially.

All of these are rather workarounds so I don't mind your approach (3).

Best regards,
Krzysztof

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