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[66.90.144.107]) by smtp.gmail.com with ESMTPSA id bx25-20020a056830601900b0066c312b044dsm2988953otb.27.2022.10.31.10.14.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 31 Oct 2022 10:14:28 -0700 (PDT) Received: (nullmailer pid 3021775 invoked by uid 1000); Mon, 31 Oct 2022 17:14:30 -0000 Date: Mon, 31 Oct 2022 12:14:30 -0500 From: Rob Herring To: Andrew Davis Cc: Krzysztof Kozlowski , Lee Jones , Krzysztof Kozlowski , Arnd Bergmann , Linus Walleij , Geert Uytterhoeven , Daniel Tang , Fabian Vogt , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/9] ARM: dts: nspire: Use syscon-reboot to handle restart Message-ID: <20221031171430.GA2981736-robh@kernel.org> References: <20221027181337.8651-1-afd@ti.com> <20221027181337.8651-3-afd@ti.com> <050f3d65-5720-9c97-1930-bc458c4c2fb8@linaro.org> <4236ab07-6ad3-efcd-7d5e-c244581d2944@linaro.org> <0025ec36-0632-b79e-beba-cf838018a704@ti.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <0025ec36-0632-b79e-beba-cf838018a704@ti.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221031_101432_597365_DA9D2EEF X-CRM114-Status: GOOD ( 68.91 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Oct 31, 2022 at 09:30:45AM -0500, Andrew Davis wrote: > On 10/27/22 4:27 PM, Krzysztof Kozlowski wrote: > > On 27/10/2022 17:07, Andrew Davis wrote: > > > On 10/27/22 2:33 PM, Krzysztof Kozlowski wrote: > > > > On 27/10/2022 14:13, Andrew Davis wrote: > > > > > Writing this bit can be handled by the syscon-reboot driver. > > > > > Add this node to DT. > > > > > > > > > > Signed-off-by: Andrew Davis > > > > > Reviewed-by: Linus Walleij > > > > > Tested-by: Fabian Vogt > > > > > Reviewed-by: Fabian Vogt > > > > > --- > > > > > arch/arm/boot/dts/nspire.dtsi | 7 +++++++ > > > > > 1 file changed, 7 insertions(+) > > > > > > > > > > diff --git a/arch/arm/boot/dts/nspire.dtsi b/arch/arm/boot/dts/nspire.dtsi > > > > > index bb240e6a3a6f..48fbc9d533c3 100644 > > > > > --- a/arch/arm/boot/dts/nspire.dtsi > > > > > +++ b/arch/arm/boot/dts/nspire.dtsi > > > > > @@ -172,7 +172,14 @@ rtc: rtc@90090000 { > > > > > }; > > > > > misc: misc@900a0000 { > > > > > + compatible = "ti,nspire-misc", "syscon", "simple-mfd"; > > > > > > > > You have syscon and simple-mfd, but bindings in patch #1 say only syscon. > > > > > > > > > > I'm not following, are you just saying my wording in the patch message just > > > wasn't complete? > > > > Your binding patch adds nspire compatible to the list of two items, so > > you have two items in total - nspire followed by syscon. > > > > What you implemented here is different. > > > > Is there a list of three items I can add this compatible? If instead you > mean I should go make a new binding, just say so :) An MFD should define its own schema file. The original intent of syscon.yaml was for just single nodes with 'syscon' (and a specific compatible). Adding in simple-mfd was probably a mistake. Certainly we need to rework the schema as you should get a warning in this case. > > > Or are you saying something more about nodes that are both syscon and simple-mfd? > > > In that case, having both syscon and simple-mfd seems rather common, looks like > > > you added the rule for it[0]. > > > > > > Thinking on this, they almost represent the same thing. simple-mfd says "my child > > > nodes should be considered devices", why do we need that? Couldn't we simply state > > > that "syscon" node's children are always devices, I mean what else could they be, > > > syscon is an MFD after all (and lives in drivers/mfd/). > > > > No, syscon is not an MFD. Syscon means system controller and alone it > > does not have children. > > > > The binding lives in devicetree/bindings/*mfd*/, it is mentioned as one > in devicetree/bindings/mfd/mfd.txt. If it is not an MFD then the bindings > are giving out mixed signals here.. > > > > > > > "syscon" often just says, others can use the registers within this node, so as a > > > different option, make "syscon" a property of "simple-mfd" nodes. I'm seeing all > > > these examples of devices that should have been children of the "syscon" device, > > > but instead use > > > > > > regmap = <&x>; > > > syscon = <&x>; > > > > > > or similar and put the device node out somewhere random. And in those cases, > > > wouldn't it have been more correct to use the normal "reg" and "regions" to > > > define the registers belonging to the child node/device?.. > > > > Sorry, I do not follow. How this is even related to your patch? > > > > Your bindings say A, DTS say B. A != B. This needs fixing. > > > > I said it was compatible with "syscon", not that it is incompatible > with "simple-mfd" devices. > > What I've done here gives no dtbs_check warnings and > "devicetree/bindings/mfd/mfd.txt" explicitly allows what I am doing. > Unless we do not consider the old bindings valid? Only that the example is not because it doesn't have a specific compatible. What needs to be clarified is that MFDs must define all the child nodes whether they are 'simple' or not. > If so, would you > like me to convert mfd.txt to yaml, just let me know. No, because I don't think there is anything to define as a schema. > > Unless you are asking me what your device is in general. This I don't > > really know, but if you want to use it as regmap provider for system > > registers and as a parent of syscon-based reboot device, then your > > device is syscon and simple-mfd. With a specific compatible. Was this > > your question? > > > > Yes, I would like to use it as a regmap provider, my question here is > a much more general one: why do I need to specify that in device tree? > That is not a hardware description, my hardware is not "regmap" hardware. > This "syscon" stuff feels like a bodge to make the Linux drivers and bus > frameworks interact the way we want. Bingo! It's a hint for create a regmap. We could just have a compatible list in the kernel for compatibles needing a regmap. Maybe that list would be too long though. So call it h/w description for this h/w is referenced by other places. > I know at this point this has little to do with this series, but I'd like > to just think this out for a moment. The latest Devicetree Specification > talks about "simple-bus" as a special compatible that communicates that > child nodes with compatible strings need probed also. ("simple-mfd" seems > to be used the same way but without needing a "ranges" property..) Yes, both cases are saying there is no dependency or setup of the parent needs. If the child nodes depend on the regmap, then it's not a 'simple-mfd' IMO. Therefore 'syscon' together with 'simple-mfd' is wrong unless it's other nodes that need the regmap. The schema can't really check that. > Both of these are properties of a node, not something a device is "compatible" > with. "compatibles" are also supposed to be listed "from most specific to > most general", so which is more specific, "simple-mfd" or "syscon", etc.. I would say 'syscon' is more specific if I have to pick. It implies some registers exist. 'simple-mfd' should mean there are no parent resources (...the children depend on). We've probably got enough of a mixture of the order, it wouldn't be worth the effort to try to enforce the order here. > Seems like Rob might agree[0], these are not really compatibles. We cant fix > history, but for new nodes, instead of growing the problem and forcing these to > be overloaded compatibles, we allow these to become new standard node properties. > > For instance: > > main_conf: syscon@43000000 { > compatible = "ti,j721e-system-controller"; > reg = <0x0 0x43000000 0x0 0x20000>; > > simple-bus; > syscon; Umm, no. This ship already sailed and we don't need a 2nd way to do things. Rob _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel