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Mon, 27 Jan 2025 04:09:51 -0800 (PST) Received: from [192.168.1.20] ([178.197.218.98]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38c2a17d697sm10719821f8f.29.2025.01.27.04.09.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 27 Jan 2025 04:09:51 -0800 (PST) Message-ID: <74ee6d9b-fd78-4d8a-a94f-b2c4dc794b60@linaro.org> Date: Mon, 27 Jan 2025 13:09:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/5] dt-bindings: mfd: syscon: Add ti,am62-ddr-pmctrl To: Andrew Davis , Markus Schneider-Pargmann Cc: Lee Jones , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Siddharth Vadapalli , Nishanth Menon , Vignesh Raghavendra , Tero Kristo , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org References: <20250122-topic-am62-dt-syscon-v6-13-v1-0-515d56edc35e@baylibre.com> <20250122-topic-am62-dt-syscon-v6-13-v1-2-515d56edc35e@baylibre.com> <20250124-heavy-jaybird-of-vitality-4cbe24@krzk-bin> <20250124-able-beagle-of-prowess-f5eb7a@krzk-bin> <639b4e3a-3f68-4fba-aa33-c46dcb6fc88f@linaro.org> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzysztof.kozlowski@linaro.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250127_040954_058607_1B3C4AF1 X-CRM114-Status: GOOD ( 32.50 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 24/01/2025 23:35, Andrew Davis wrote: > On 1/24/25 10:48 AM, Krzysztof Kozlowski wrote: >> On 24/01/2025 17:05, Markus Schneider-Pargmann wrote: >>> Hi Krzysztof, >>> >>> On Fri, Jan 24, 2025 at 09:22:54AM +0100, Krzysztof Kozlowski wrote: >>>> On Fri, Jan 24, 2025 at 09:19:49AM +0100, Krzysztof Kozlowski wrote: >>>>> On Wed, Jan 22, 2025 at 11:24:33AM +0100, Markus Schneider-Pargmann wrote: >>>>>> Add compatible for ti,am62-ddr-pmctrl to the list. There is a DDR pmctrl >>>>>> register in the wkup-conf register space of am62a and am62p. This >>>>>> register controls DDR power management. >>>>>> >>>>>> Signed-off-by: Markus Schneider-Pargmann >>>>>> --- >>>>>> Documentation/devicetree/bindings/mfd/syscon.yaml | 2 ++ >>>>>> 1 file changed, 2 insertions(+) >>>>> >>>>> Acked-by: Krzysztof Kozlowski >>>> >>>> Un-acked, I missed the point that you really speak in commit msg about >>>> register and you really treat one register is a device. I assumed you >>>> only need that register from this device, but no. That obviously is not >>>> what this device is. Device is not a single register among 10000 others. >>>> IOW, You do not have 10000 devices there. >>> >>> Do I understand you correctly that the whole register range of the >>> wkup_conf node as seen in arch/arm64/boot/dts/ti/k3-am62a-wakeup.dtsi >>> should be considered a single syscon device? >> >> I don't have the datasheets (and not my task to actually check this), >> but you should probably follow datasheet. I assume it describes what is >> the device, more or less. >> >> I assume entire wkup_conf is considered a device. >> >>> >>> Unfortunately wkup_conf is modeled as a simple-bus with currently 5 >>> subnodes defined of which 4 of them consist of a single register. Most >>> of them are syscon as well. So I think I can't change the simple-bus >>> back to syscon. >> >> Huh... Maybe TI folks will help us understand why such design was chosen. >> > > Many of the devices inside the wkup_conf are already modeled as such. > Clocks and muxes for instance already have drivers and bindings, this > is nothing new to TI. > > If we just use a blank "syscon" over the entire region we would end up > with drivers that use phandles to the top level wkup_conf node and > poke directly the registers they need from that space. > > Would you rather have > > some-device { > ti,epwm_tbclk = <&wkup_conf>; > } > > or > > some-device { > clocks = <&epwm_tbclk 0>; > } How is this comparable? These are clocks. You would have clocks property in both cases. > > with that epwm_tbclk being a proper clock node inside wkup_conf? > I would much prefer the second, even though the clock node > only uses a single register. And in the first case, we would need > to have the offset into the wkup_conf space hard-coded in the > driver for each new SoC. Eventually all that data would need to be > put in tables and we end up back to machine board files.. > > I'm not saying every magic number in all drivers should > be offloaded into DT, but there is a line somewhere between > that and having the DT simply contain the SoC's name compatible That's not the question here. > and all other data going into the kernel. That line might be a > personal preference, so my question back is: what is wrong > if we do want "1000 new syscons per each register" for our > SoCs DT? Because it is false representation of hardware. You do not have 1000 devices. You have only one device. > > (and the number is not 1000, scanning the kernel I can see > the largest wkup_conf region node we have today has a grand > total number sub-nodes of 6) But what is being added here is device per each register, not per feature. Best regards, Krzysztof