From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 457FEC433F5 for ; Sat, 5 Feb 2022 21:59:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378863AbiBEV7t (ORCPT ); Sat, 5 Feb 2022 16:59:49 -0500 Received: from mailserv1.kapsi.fi ([91.232.154.157]:52990 "EHLO mailserv1.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1351002AbiBEV7t (ORCPT ); Sat, 5 Feb 2022 16:59:49 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=ext.kapsi.fi; s=20161220; h=Subject:Content-Transfer-Encoding:MIME-Version: References:In-Reply-To:Message-Id:Date:Cc:To:From:Sender:Reply-To: Content-Type:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=6Z08zw8GPYqaS2TD7Ieq2MqRlSnLB18cTeBXjvmX1cE=; b=DbGUbspCHFW47QvBKZEmj/Zaeq UjgDxbo6xF3Ii6w00HSM47B/QBiI4132+3Dlg2bagsqY9OGdfZAa7u8z7GIJSMoJC+sM0h8VBe8n3 PvSlm5H6r76UQMzXfNFQS8B+H9f2RLFii6KyRARNUpLEZ+1NsS5m96ZEJGjsehsnQEUvL9rvLAYQL UWqDhCQOrcglw1mF2CTb8iB2DOwQzDRU5th66OdRE2yCUenFEge4g7dY55uJxtx8zV6AT4T89XmBX DtZkRaGzkB4ld2Hu9oaX5vNT43dadKFDPuIzOy9dGRRKq3ZuSXtn6uDnIZBHNB/WMvAbjynEeBuGk 0YatFeeg==; Received: from 246-30-196-88.dyn.estpak.ee ([88.196.30.246]:49929 helo=localhost) by mailserv1.kapsi.fi with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1nGT5p-0006cQ-9m; Sat, 05 Feb 2022 23:59:42 +0200 Received: by localhost (sSMTP sendmail emulation); Sat, 05 Feb 2022 23:59:40 +0200 From: Mauri Sandberg To: bgolaszewski@baylibre.com, brgl@bgdev.pl Cc: andy.shevchenko@gmail.com, geert+renesas@glider.be, linus.walleij@linaro.org, linux-gpio@vger.kernel.org, robh+dt@kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, drew@beagleboard.org, Mauri Sandberg , Rob Herring Date: Sat, 5 Feb 2022 23:59:17 +0200 Message-Id: <20220205215918.8924-2-maukka@ext.kapsi.fi> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220205215918.8924-1-maukka@ext.kapsi.fi> References: <20210325122832.119147-1-sandberg@mailfence.com> <20220205215918.8924-1-maukka@ext.kapsi.fi> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SA-Exim-Connect-IP: 88.196.30.246 X-SA-Exim-Mail-From: maukka@ext.kapsi.fi Subject: [RESEND v8 1/2] dt-bindings: gpio-cascade: add documentation X-SA-Exim-Version: 4.2.1 (built Tue, 02 Aug 2016 21:08:31 +0000) X-SA-Exim-Scanned: Yes (on mailserv1.kapsi.fi) Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org Add documentation for a general GPIO cascade. It allows building one-to-many cascades of GPIO lines using multiplexer to choose the cascaded line. Signed-off-by: Mauri Sandberg Reviewed-by: Rob Herring Reviewed-by: Linus Walleij --- v7 -> v8: - added Reviewed-by tag by Linus v6 -> v7: - no changes v5 -> v6: - added Reviewed-by tag by Rob v4 -> v5: - renamed gpio-mux-input -> gpio-cascade - changed vague term 'pin' to 'upstream line' - added more verbose description for the module - added missing 'mux-controls' entry - dropped Tested-by and Reviewed-by due to changes in bindings v3 -> v4: - Changed author email - Included Tested-by and Reviewed-by from Drew v2 -> v3: added a complete example on dual 4-way multiplexer v1 -> v2: added a little bit more text in the binding documenation --- .../bindings/gpio/gpio-cascade.yaml | 103 ++++++++++++++++++ 1 file changed, 103 insertions(+) create mode 100644 Documentation/devicetree/bindings/gpio/gpio-cascade.yaml diff --git a/Documentation/devicetree/bindings/gpio/gpio-cascade.yaml b/Documentation/devicetree/bindings/gpio/gpio-cascade.yaml new file mode 100644 index 000000000000..46248f8e2ba5 --- /dev/null +++ b/Documentation/devicetree/bindings/gpio/gpio-cascade.yaml @@ -0,0 +1,103 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/gpio/gpio-cascade.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Generic GPIO cascade + +maintainers: + - Mauri Sandberg + +description: | + A generic GPIO cascade + + This hardware construction cascades (multiplexes) several GPIO lines from + one-to-many using a software controlled multiplexer. The most common use + case is probably reading several inputs by switching the multiplexer over + several input lines, which in practice works well since input lines has + high impedance. + + Constructions with multiplexed outputs are also possible using open drain + electronics. + + The number of cascaded GPIO lines is limited by the technology used to + switch over the cascaded lines. There are readily available dual/triple + 4-to-1 multiplexers, for example, and others. + + Illustration (pins used to drive the multiplexer are omitted for clarity) + + /|---- Cascaded GPIO line 0 + Upstream | |---- Cascaded GPIO line 1 + GPIO line ----+ | . + | | . + \|---- Cascaded GPIO line n + +properties: + compatible: + enum: + - gpio-cascade + + gpio-controller: true + + '#gpio-cells': + const: 2 + + mux-controls: + minItems: 1 + maxItems: 1 + description: | + The mux controller that will be driving the GPIO cascade. + + upstream-gpios: + description: | + The GPIO line used as the upstream line will convey the status to/from + cascaded GPIO lines. In an input mode, by using this line, it is + possible to read the status from selected cascaded GPIO line. + + In an output mode the status of the upstream GPIO will be conveyed to + the selected cascaded GPIO line. + +required: + - compatible + - gpio-controller + - "#gpio-cells" + - mux-controls + - upstream-gpios + +additionalProperties: false + +examples: + - | + #include + mux: mux-controller { + compatible = "gpio-mux"; + #mux-control-cells = <0>; + + mux-gpios = <&gpio 9 GPIO_ACTIVE_HIGH>, + <&gpio 11 GPIO_ACTIVE_HIGH>; + }; + + gpio2: key-mux1 { + compatible = "gpio-cascade"; + mux-controls = <&mux>; + + gpio-controller; + #gpio-cells = <2>; + + // GPIOs used by this node, upstream pin + upstream-gpios = <&gpio 12 GPIO_ACTIVE_HIGH>; + }; + + gpio3: key-mux2 { + compatible = "gpio-cascade"; + mux-controls = <&mux>; + + gpio-controller; + #gpio-cells = <2>; + + // GPIOs used by this node, upstream pin + upstream-gpios = <&gpio 14 GPIO_ACTIVE_HIGH>; + }; + +... -- 2.25.1