From: Andre Przywara <andre.przywara@arm.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: "Jernej Škrabec" <jernej.skrabec@gmail.com>,
"Samuel Holland" <samuel@sholland.org>,
"Chen-Yu Tsai" <wens@csie.org>,
linux-sunxi@lists.linux.dev,
"Palmer Dabbelt" <palmer@dabbelt.com>,
"Paul Walmsley" <paul.walmsley@sifive.com>,
"Albert Ou" <aou@eecs.berkeley.edu>,
linux-riscv@lists.infradead.org,
"Heiko Stübner" <heiko@sntech.de>,
"Rob Herring" <robh+dt@kernel.org>,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>
Subject: Re: [PATCH 06/12] riscv: dts: allwinner: Add the D1 SoC base devicetree
Date: Tue, 16 Aug 2022 12:00:50 +0100 [thread overview]
Message-ID: <20220816120050.07dc2416@donnerap.cambridge.arm.com> (raw)
In-Reply-To: <b5401052-e803-9788-64d6-82b2737533ce@linaro.org>
On Tue, 16 Aug 2022 12:42:39 +0300
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:
Hi,
> On 16/08/2022 12:25, Jernej Škrabec wrote:
> > Dne torek, 16. avgust 2022 ob 11:12:05 CEST je Heiko Stübner napisal(a):
> >> Am Dienstag, 16. August 2022, 09:49:58 CEST schrieb Jernej Škrabec:
> >>> Dne torek, 16. avgust 2022 ob 09:41:45 CEST je Krzysztof Kozlowski
> > napisal(a):
> >>>> On 15/08/2022 08:08, Samuel Holland wrote:
> >>>>> +
> >>>>> + de: display-engine {
> >>>>> + compatible = "allwinner,sun20i-d1-display-engine";
> >>>>> + allwinner,pipelines = <&mixer0>, <&mixer1>;
> >>>>> + status = "disabled";
> >>>>> + };
> >>>>> +
> >>>>> + osc24M: osc24M-clk {
> >>>>
> >>>> lowercase
> >>>>
> >>>>> + compatible = "fixed-clock";
> >>>>> + clock-frequency = <24000000>;
> >>>>
> >>>> This is a property of the board, not SoC.
> >>>
> >>> SoC needs 24 MHz oscillator for correct operation, so each and every board
> >>> has it. Having it here simplifies board DT files.
> >>
> >> I guess the oscillator is a separate component on each board, right?
> >
> > Correct.
> >
> >> And DT obvious is meant to describe the hardware - independently from
> >> implementation-specific choices.
> >
> > There is no choice in this case. 24 MHz crystal has to be present.
> >
> > FWIW, including crystal node in SoC specific DTSI is already common pattern in
> > Allwinner ARM SoC DTSI files.
> >
> >>
> >> Starting to discuss which exceptions to allow then might lead to even more
> >> exceptions.
> >>
> >> Also having to look for a board-component in the soc dtsi also is surprising
> >> if one gets to the party later on :-) .
> >
> > As I said, if one is accustomed to Allwinner ARM DT development, it would be
> > more surprising to include 24 MHz crystal node in each and every board DT.
>
> It's same everywhere. Allwinner, Exynos, iMX, Qualcomm. Everywhere this
> is a part of the board, so even if oscillator frequency is fixed (as in
> 99% of cases although some SoCs I think might just allow to implement
> one of few), still this is a property of the board. Because:
> 1. DTSI describes the SoC part, not board.
> 2. So the DTS developer is a bit more conscious about his design.
1) is certainly true, but indeed most platforms put the base
crystal oscillator in the SoC .dtsi: I just sampled Rockchip (rk3399.dtsi,
rk356x.dtsi, rk3328.dtsi), Amlogic (meson-g12-common.dtsi), ActionSemi (s[79]00.dtsi),
Qualcomm (msm8916.dtsi, sm8450.dtsi, sc7180.dtsi), Freescale (imx8mm.dtsi,
imx8qxp.dtsi), Realtek (rtd129x.dtsi), Broadcom (bcm283x.dtsi), Mediatek
(mt8183.dtsi, mt8516.dtsi). The list probably goes on (I just stopped
here).
I think one reason might be that this is so central to the whole SoC
operation, that it's already referenced multiple times in the base .dtsi.
And having a yet unresolved reference in the .dtsi looks dodgy.
NVidia seems to omit a base oscillator (maybe it's implicit in their
binding design), Marvell doesn't use a fixed-clock (but still puts their
base clock in armada-37xx.dtsi).
Exynos and Renesas put a *stub* fixed-clock in the .dtsi, and set the
frequency in the board .dts files. Would this be a compromise?
Cheers,
Andre
> Keeping things in SoC DTSI just because it simplifies DTS is not correct
> IMHO. So again - like in several other cases - minimum the frequency is
> property of the board, not the SoC DTSI.
>
> Everywhere. Allwinner is not special to receive exceptions.
>
> Best regards,
> Krzysztof
>
next prev parent reply other threads:[~2022-08-16 11:36 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-08-15 5:08 [PATCH 00/12] riscv: Allwinner D1 platform support Samuel Holland
2022-08-15 5:08 ` [PATCH 01/12] MAINTAINERS: Match the sun20i family of Allwinner SoCs Samuel Holland
2022-08-15 17:06 ` Heiko Stübner
2022-08-15 5:08 ` [PATCH 02/12] dt-bindings: riscv: Add T-HEAD C906 and C910 compatibles Samuel Holland
2022-08-15 17:07 ` Heiko Stübner
2022-08-16 17:34 ` Rob Herring
2022-11-04 2:57 ` Icenowy Zheng
2022-11-20 11:23 ` Conor Dooley
2022-11-20 11:25 ` Conor Dooley
2022-08-15 5:08 ` [PATCH 03/12] dt-bindings: vendor-prefixes: Add Allwinner D1 board vendors Samuel Holland
2022-08-15 17:12 ` Heiko Stübner
2022-08-16 17:34 ` Rob Herring
2022-08-15 5:08 ` [PATCH 04/12] dt-bindings: riscv: Add Allwinner D1 board compatibles Samuel Holland
2022-08-16 7:39 ` Krzysztof Kozlowski
2022-08-16 9:02 ` Heiko Stübner
2022-08-16 9:12 ` Heiko Stübner
2022-08-16 17:35 ` Rob Herring
2022-08-15 5:08 ` [PATCH 05/12] riscv: Add the Allwinner SoC family Kconfig option Samuel Holland
2022-08-15 16:56 ` Conor.Dooley
2022-08-16 9:17 ` Heiko Stübner
2022-08-16 9:23 ` Conor.Dooley
2022-08-15 17:13 ` Heiko Stübner
2022-08-15 5:08 ` [PATCH 06/12] riscv: dts: allwinner: Add the D1 SoC base devicetree Samuel Holland
2022-08-15 13:11 ` Andre Przywara
2022-08-15 17:01 ` Conor.Dooley
2022-08-20 17:24 ` Samuel Holland
2022-08-20 17:29 ` Conor.Dooley
2022-08-21 6:45 ` Icenowy Zheng
2022-08-21 10:04 ` Conor.Dooley
2022-08-22 11:46 ` Geert Uytterhoeven
2022-08-22 12:13 ` Conor.Dooley
2022-08-22 12:29 ` Andre Przywara
2022-08-22 12:31 ` Geert Uytterhoeven
2022-08-22 13:56 ` Conor.Dooley
2022-08-22 15:29 ` Jessica Clarke
2022-09-09 3:42 ` Samuel Holland
2022-09-09 7:10 ` Geert Uytterhoeven
2022-09-21 7:49 ` Geert Uytterhoeven
2022-08-22 10:50 ` Andre Przywara
2022-08-16 7:41 ` Krzysztof Kozlowski
2022-08-16 7:49 ` Jernej Škrabec
2022-08-16 9:12 ` Heiko Stübner
2022-08-16 9:25 ` Jernej Škrabec
2022-08-16 9:42 ` Krzysztof Kozlowski
2022-08-16 11:00 ` Andre Przywara [this message]
2022-08-16 11:11 ` Krzysztof Kozlowski
2022-08-16 11:12 ` Krzysztof Kozlowski
2022-08-16 11:34 ` Conor.Dooley
2022-08-22 11:40 ` Geert Uytterhoeven
2022-08-16 9:11 ` Heiko Stübner
2022-08-17 8:29 ` Krzysztof Kozlowski
2022-08-19 22:19 ` Conor.Dooley
2022-08-15 5:08 ` [PATCH 07/12] riscv: dts: allwinner: Add Allwinner D1 Nezha devicetree Samuel Holland
2022-08-15 17:37 ` Conor.Dooley
2022-08-15 18:34 ` Conor.Dooley
2022-08-16 8:55 ` Heiko Stübner
2022-08-19 22:10 ` Conor.Dooley
2022-08-21 7:06 ` Icenowy Zheng
2022-09-04 20:10 ` Peter Korsgaard
2022-09-09 4:37 ` Samuel Holland
2022-09-09 7:18 ` Conor.Dooley
2022-09-09 8:11 ` Heiko Stübner
2022-09-09 19:04 ` Jessica Clarke
2022-09-03 15:21 ` Peter Korsgaard
2022-08-15 5:08 ` [PATCH 08/12] riscv: dts: allwinner: Add Sipeed Lichee RV devicetrees Samuel Holland
2022-08-15 5:08 ` [PATCH 09/12] riscv: dts: allwinner: Add MangoPi MQ Pro devicetree Samuel Holland
2022-08-15 5:08 ` [PATCH 10/12] riscv: dts: allwinner: Add Dongshan Nezha STU devicetree Samuel Holland
2022-08-15 5:08 ` [PATCH 11/12] riscv: dts: allwinner: Add ClockworkPi and DevTerm devicetrees Samuel Holland
2022-08-15 5:08 ` [PATCH 12/12] riscv: defconfig: Enable the Allwinner D1 platform and drivers Samuel Holland
2022-08-15 7:05 ` [PATCH 00/12] riscv: Allwinner D1 platform support Conor.Dooley
2022-08-15 17:12 ` Conor.Dooley
2022-08-16 2:42 ` Samuel Holland
2022-08-16 6:38 ` Conor.Dooley
2022-09-01 18:10 ` Palmer Dabbelt
2022-09-02 5:42 ` Conor.Dooley
2022-09-06 20:29 ` Jernej Škrabec
2022-09-07 20:43 ` Conor.Dooley
2022-09-08 7:00 ` Geert Uytterhoeven
2022-09-08 9:04 ` Arnd Bergmann
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