[02/11] dt-bindings: serial: snps-dw-apb-uart: Relax dma-names order constraint

Commit 370f696e4474 ("dt-bindings: serial: snps-dw-apb-uart: add dma &
dma-names properties") documented dma-names property to handle Allwiner
D1 dtbs_check warnings, but relies on a strict rx->tx ordering, which is
the reverse of what a different board expects:

  rk3326-odroid-go2.dtb: serial@ff030000: dma-names:0: 'rx' was expected

A quick and incomplete check shows the inconsistency is present in many
other DT files:

$ git grep -A10 snps,dw-apb-uart | grep dma-names | sort -u
arch/arm64/boot/dts/rockchip/px30.dtsi-         dma-names = "tx", "rx";
arch/arm64/boot/dts/rockchip/rk3328.dtsi-       dma-names = "tx", "rx";
arch/arm64/boot/dts/rockchip/rk3588s.dtsi-      dma-names = "tx", "rx";
arch/arm/boot/dts/rk3066a.dtsi-                 dma-names = "tx", "rx";
arch/arm/boot/dts/rk3128.dtsi-                  dma-names = "tx", "rx";
arch/arm/boot/dts/rk3288.dtsi-                  dma-names = "tx", "rx";
arch/arm/boot/dts/rv1126.dtsi-                  dma-names = "tx", "rx";
arch/arm/boot/dts/socfpga.dtsi-                 dma-names = "tx", "rx";
arch/arm/boot/dts/sun6i-a31.dtsi-               dma-names = "rx", "tx";
arch/arm/boot/dts/sun8i-a23-a33.dtsi-           dma-names = "rx", "tx";
arch/arm/boot/dts/sun8i-v3s.dtsi-               dma-names = "rx", "tx";
arch/arm/boot/dts/sunxi-h3-h5.dtsi-             dma-names = "rx", "tx";
arch/riscv/boot/dts/allwinner/sunxi-d1s-t113.dtsi-  dma-names = "rx", "tx";

Do not enforce the order of the dma-names items.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
---
 .../devicetree/bindings/serial/snps-dw-apb-uart.yaml   | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

On Fri, Mar 17, 2023 at 12:21:41PM +0200, Cristian Ciocaltea via Alsa-devel wrote:
> Date: Fri, 17 Mar 2023 12:21:41 +0200
> From: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
> To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>, Sudeep Holla
>  <sudeep.holla@arm.com>, Cristian Marussi <cristian.marussi@arm.com>, Rob
>  Herring <robh+dt@kernel.org>, Krzysztof Kozlowski
>  <krzysztof.kozlowski+dt@linaro.org>, Greg Kroah-Hartman
>  <gregkh@linuxfoundation.org>, Liam Girdwood <lgirdwood@gmail.com>, Mark
>  Brown <broonie@kernel.org>, Nicolas Frattaroli
>  <frattaroli.nicolas@gmail.com>, Heiko Stuebner <heiko@sntech.de>, Jaroslav
>  Kysela <perex@perex.cz>, Takashi Iwai <tiwai@suse.com>, Paul Walmsley
>  <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou
>  <aou@eecs.berkeley.edu>, Daniel Drake <drake@endlessm.com>, Katsuhiro
>  Suzuki <katsuhiro@katsuster.net>
> CC: linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
>  linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org,
>  alsa-devel@alsa-project.org, linux-rockchip@lists.infradead.org,
>  linux-riscv@lists.infradead.org, kernel@collabora.com
> Subject: Re: [PATCH 02/11] dt-bindings: serial: snps-dw-apb-uart: Relax
>  dma-names order constraint
> Message-ID: <8ae57fe3-56aa-7e50-3eaa-a12a40657baf@collabora.com>
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
>  Thunderbird/102.7.2

There is something strange going on with your mails as there are 2 
copies in the archives with the 2nd one getting the header twice. It's 
coming from the alsa-devel list.

> 
> On 3/17/23 10:31, Krzysztof Kozlowski wrote:
> > On 15/03/2023 12:47, Cristian Ciocaltea wrote:
> > > Commit 370f696e4474 ("dt-bindings: serial: snps-dw-apb-uart: add dma &
> > > dma-names properties") documented dma-names property to handle Allwiner
> > > D1 dtbs_check warnings, but relies on a strict rx->tx ordering, which is
> > > the reverse of what a different board expects:
> > > 
> > >    rk3326-odroid-go2.dtb: serial@ff030000: dma-names:0: 'rx' was expected
> > > 
> > > A quick and incomplete check shows the inconsistency is present in many
> > > other DT files:
> > 
> > Why not fixing the DTS? The properties should have fixed order.
> 
> I was initially concerned about the risk of a potential ABI breakage, but I
> think that's not really a problem since dma-names is not directly accessed
> in the driver and DT Kernel API doesn't rely on a particular order.
> 
> If there are no objections, I would switch the order in the binding to
> tx->rx, since that's what most of the DTS use, and fix the remaining ones.
> 
> > Best regards,
> > Krzysztof
> 
> Thanks,
> Cristian