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- To: Conor Dooley <conor@xxxxxxxxxx>, Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
- Subject: Re: [PATCH 02/11] dt-bindings: serial: snps-dw-apb-uart: Relax dma-names order constraint
- From: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
- Date: Fri, 17 Mar 2023 19:43:53 +0200
- Cc: Sudeep Holla <sudeep.holla@xxxxxxx>, Cristian Marussi <cristian.marussi@xxxxxxx>, Rob Herring <robh+dt@xxxxxxxxxx>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@xxxxxxxxxx>, Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>, Liam Girdwood <lgirdwood@xxxxxxxxx>, Mark Brown <broonie@xxxxxxxxxx>, Nicolas Frattaroli <frattaroli.nicolas@xxxxxxxxx>, Heiko Stuebner <heiko@xxxxxxxxx>, Takashi Iwai <tiwai@xxxxxxxx>, Paul Walmsley <paul.walmsley@xxxxxxxxxx>, Palmer Dabbelt <palmer@xxxxxxxxxxx>, Albert Ou <aou@xxxxxxxxxxxxxxxxx>, Daniel Drake <drake@xxxxxxxxxxxx>, Katsuhiro Suzuki <katsuhiro@xxxxxxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, devicetree@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-serial@xxxxxxxxxxxxxxx, alsa-devel@xxxxxxxxxxxxxxxx, linux-rockchip@xxxxxxxxxxxxxxxxxxx, linux-riscv@xxxxxxxxxxxxxxxxxxx, kernel@xxxxxxxxxxxxx
- In-reply-to: <13cb8dbd-994c-4b38-b715-44a3bf3d278d@spud>
- References: <20230315114806.3819515-1-cristian.ciocaltea@collabora.com> <20230315114806.3819515-3-cristian.ciocaltea@collabora.com> <3679f2d0-55f0-1710-abc2-b268b6fc6969@linaro.org> <8ae57fe3-56aa-7e50-3eaa-a12a40657baf@collabora.com> <80796828-7b38-184a-2e8e-3cfe9158b67f@linaro.org> <13cb8dbd-994c-4b38-b715-44a3bf3d278d@spud>
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On 3/17/23 18:26, Conor Dooley wrote:
On Fri, Mar 17, 2023 at 04:54:47PM +0100, Krzysztof Kozlowski wrote:
On 17/03/2023 11:21, Cristian Ciocaltea wrote:
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.
Since we added the order recently, I rather assume it is the correct or
preferred one.
IIRC I checked around the other serial bindings & there was not a
consistent order that all serial bindings used, so I picked the order that
was used across the various allwinner boards that do use dma-names.
Thanks for clarifying this, Conor! Would it be fine to switch to tx->rx
order as it requires less changes to fix the inconsistencies?
Before changing dts files, it's probably a good idea to make sure that
the dma-names are not used somewhere outside of Linux.
Right, that means we cannot exclude the ABI breakage concern. Not sure
how easy would be to actually verify this. Hence I wonder if there is
really no chance to allow the flexible order in the binding..
Cheers,
Conor
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