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[73.183.52.120]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-50bb2e0fe31sm63567841cf.20.2026.03.30.08.09.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2026 08:09:06 -0700 (PDT) Date: Mon, 30 Mar 2026 11:09:03 -0400 From: Brian Masney To: "Miquel Raynal (Schneider Electric)" Cc: Michael Turquette , Stephen Boyd , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Thomas Gleixner , Olivia Mackall , Herbert Xu , Jayesh Choudhary , "David S. Miller" , Christian Marangi , Antoine Tenart , Geert Uytterhoeven , Magnus Damm , Thomas Petazzoni , Pascal EBERHARD , Wolfram Sang , linux-clk@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Herve Codina Subject: Re: [PATCH 10/16] clk: Add support for clock nexus dt bindings Message-ID: References: <20260327-schneider-v7-0-rc1-crypto-v1-0-5e6ff7853994@bootlin.com> <20260327-schneider-v7-0-rc1-crypto-v1-10-5e6ff7853994@bootlin.com> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260327-schneider-v7-0-rc1-crypto-v1-10-5e6ff7853994@bootlin.com> User-Agent: Mutt/2.3.0 (2026-01-25) On Fri, Mar 27, 2026 at 09:09:32PM +0100, Miquel Raynal (Schneider Electric) wrote: > A nexus node is some kind of parent device abstracting the outer > connections. They are particularly useful for describing connectors-like > interfaces but not only. Certain IP blocks will typically include inner > blocks and distribute resources to them. > > In the case of clocks, there is already the concept of clock controller, > but this usually indicates some kind of control over the said clock, > ie. gate or rate control. When there is none of this, an existing > approach is to reference the upper clock, which is wrong from a hardware > point of view. > > Nexus nodes are already part of the device-tree specification and clocks > are already mentioned: > https://github.com/devicetree-org/devicetree-specification/blob/v0.4/source/chapter2-devicetree-basics.rst#nexus-nodes-and-specifier-mapping > > Following the introductions of nexus nodes support for interrupts, gpios > and pwms, here is the same logic applied again to the clk subsystem, > just by transitioning from of_parse_phandle_with_args() to > of_parse_phandle_with_args_map(): > > * Nexus OF support: > commit bd6f2fd5a1d5 ("of: Support parsing phandle argument lists through a nexus node") > * GPIO adoption: > commit c11e6f0f04db ("gpio: Support gpio nexus dt bindings") > * PWM adoption: > commit e71e46a6f19c ("pwm: Add support for pwm nexus dt bindings") > > Expected Nexus properties supported: > - clock-map: maps inner clocks to inlet clocks, > - clock-map-mask: specifier cell(s) which will be remapped, > - clock-map-pass-thru: specifier cell(s) not used for remapping, > forwarded as-is. > > In my own usage I had to deal with controllers where clock-map-mask and > clock-map-pass-thru were not relevant, but here is a made up example > showing how all these properties could go together: > > Example: > soc_clk: clock-controller { > #clock-cells = <2>; > }; > > container: container { > #clock-cells = <2>; > clock-map = <0 0 &soc_clk 2 0>, > <1 0 &soc_clk 6 0>; > clock-map-mask = <0xffffffff 0x0>; > clock-map-pass-thru = <0x0 0xffffffff>; > > child-device { > clocks = <&container 1 0>; > /* This is equivalent to <&soc_clk 6 0> */ > }; > }; > > The child device does not need to know about the outer implementation, > and only knows about what the nexus provides. The nexus acts as a > pass-through, with no extra control. > > Signed-off-by: Miquel Raynal (Schneider Electric) > Reviewed-by: Herve Codina Reviewed-by: Brian Masney