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Message-ID: <Y3/NQBzU/R6XubBf@makrotopia.org> Date: Thu, 24 Nov 2022 20:00:00 +0000 From: Daniel Golle <daniel@...rotopia.org> To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org> Cc: linux-mediatek@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, linux-pwm@...r.kernel.or, Matthias Brugger <matthias.bgg@...il.com>, Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Rob Herring <robh+dt@...nel.org>, Uwe Kleine-König <u.kleine-koenig@...gutronix.de>, Thierry Reding <thierry.reding@...il.com>, Fabien Parent <fparent@...libre.com>, Zhi Mao <zhi.mao@...iatek.com>, Sam Shih <sam.shih@...iatek.com> Subject: Re: [PATCH RESEND v2] dt-bindings: pwm: mediatek: Add compatible for MT7986 Hi Krzysztof, On Thu, Nov 24, 2022 at 02:33:35PM +0100, Krzysztof Kozlowski wrote: > On 24/11/2022 13:11, Daniel Golle wrote: > > On Thu, Nov 24, 2022 at 12:30:44PM +0100, Krzysztof Kozlowski wrote: > >> On 24/11/2022 12:03, Daniel Golle wrote: > >>> Add new compatible string for MT7986 PWM and list compatible units for > >>> existing entries. Also make sure the number of pwm1-X clocks is listed > >>> for all supported units. > >>> > >>> Signed-off-by: Daniel Golle <daniel@...rotopia.org> > >>> --- > >>> Changes since v1: list compatibles, fix pwm1-n clocks for all SoCs > >>> > >>> Rebased on linux-next and re-run scripts/get_maintainers.pl on patch to > >>> makes sure dt maintainers are included. This has been requested by > >>> Krzysztof Kozlowski. > >>> > >>> .../devicetree/bindings/pwm/pwm-mediatek.txt | 20 +++++++++++-------- > >>> 1 file changed, 12 insertions(+), 8 deletions(-) > >>> > >>> diff --git a/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt b/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt > >>> index 554c96b6d0c3..952a338e06e7 100644 > >>> --- a/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt > >>> +++ b/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt > >>> @@ -2,14 +2,15 @@ MediaTek PWM controller > >>> > >>> Required properties: > >>> - compatible: should be "mediatek,<name>-pwm": > >>> - - "mediatek,mt2712-pwm": found on mt2712 SoC. > >>> + - "mediatek,mt2712-pwm", "mediatek,mt6795-pwm": found on mt2712 SoC. > >>> - "mediatek,mt6795-pwm": found on mt6795 SoC. > >>> - - "mediatek,mt7622-pwm": found on mt7622 SoC. > >>> - - "mediatek,mt7623-pwm": found on mt7623 SoC. > >>> + - "mediatek,mt7622-pwm", "mediatek,mt8195-pwm", "mediatek,mt8183-pwm", "mediatek,mt7986-pwm": found on mt7622 SoC. > >> > >> This does not look right. What you are saying is mt7622 is compatible > >> with mt8195, which is compatible with mt8183, which is compatible with > >> mt7986. It could be true, but I feel you wanted to say something else - > >> mt7622 is compatible with one SoC which is generic and common to all > >> other implementations. > > > > MT7622 has 6 PWM channels, it does have CK_26M_SEL register and does > > not need pwm45_fixup. Hence, when using a driver made for MT8195, only > > 4 out of 6 channels woukd work. MT8183 PWM is identical to MT8195, > > hence also compatible. When using driver for MT7986, only 2 channels > > would work, but otherwise it is also compatible. > > > > So unfortunately, that one generic implementation ("common ancestor") > > does not exist and development of the PWM unit found in MediaTek SoCs > > did not necessarily increase features in more recent iterations, but > > rather just reduce or increase the number of PWM channels available. > > Ironically, the unit with least features (only 2 channels) is found in > > the most recent SoC (MT7986). > > None of these explain listing four compatibles. So do I understand correctly that in this case only the newly introduced "mediatek,mt7986-pwm" should be listed as more generic compatible after the more specific "mediatek,mt7622-pwm", everything in between should be dropped? Or only drop "mediatek,mt8195-pwm" here? I'm asking because in your message from 23/10/2022 you were quoting Devicetree specification: > "The property value consists of a concatenated list of null terminated > strings, from most specific to most general. They allow a device to > express its compatibility with a family of similar devices, potentially > allowing a single device driver to match against several devices." And we have discussed in great length (as I had misunderstood it) that this should mean that units with the lowest number of channels are to be considered the "most general" if otherwise identical. > > > > >> > >>> + - "mediatek,mt7623-pwm", "mediatek,mt7628-pwm": found on mt7623 SoC. > >>> - "mediatek,mt7628-pwm": found on mt7628 SoC. > >>> - "mediatek,mt7629-pwm": found on mt7629 SoC. > >>> - - "mediatek,mt8183-pwm": found on mt8183 SoC. > >>> - - "mediatek,mt8195-pwm", "mediatek,mt8183-pwm": found on mt8195 SoC. > >>> + - "mediatek,mt7986-pwm": found on mt7986 SoC. > >>> + - "mediatek,mt8183-pwm", "mediatek,mt7986-pwm": found on mt8183 SoC. > >>> + - "mediatek,mt8195-pwm", "mediatek,mt8183-pwm", "mediatek,mt7986-pwm": found on mt8195 SoC. > >> > >> This as well looks excessive. > > > > I agree. But it's difficult to say which one should be ommitted. So are you suggesting to drop the "mediatek,mt8183-pwm" string here? Thank you for your patience! Daniel
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