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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 98A4FC433E2 for ; Wed, 9 Sep 2020 15:12:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C700821919 for ; Wed, 9 Sep 2020 15:12:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="Lq0jJ4wh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729614AbgIIPKy (ORCPT ); Wed, 9 Sep 2020 11:10:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42674 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730064AbgIIL6C (ORCPT ); Wed, 9 Sep 2020 07:58:02 -0400 Received: from mail-lj1-x244.google.com (mail-lj1-x244.google.com [IPv6:2a00:1450:4864:20::244]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 553BBC0617A3 for ; Wed, 9 Sep 2020 04:58:01 -0700 (PDT) Received: by mail-lj1-x244.google.com with SMTP id c2so3103327ljj.12 for ; Wed, 09 Sep 2020 04:58:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=veMOlwm85HGnlMSTVN952J/Jqjc/7rvdCvDfPKEre0c=; b=Lq0jJ4whRo5WT/1EwrgGOl0XtPUPtvtGXLC81q5hE5FLoHPxnCgByqRckcoRWhj69y 8POlYqx76p1PczfUYqXfb+R7q5w0oL+bb5PyhrPpsQU6UKMKeUmSKkDaAL+s7kMke30d YiGusFifL3kjDo2Y3BUUdRoscclcabbbQiDZACAMH/75Q1mpxTyMd9tTtFm3ATcURbyg 04CbyAHdOELljt3QOr0smY9DXjCBobqHTrbDupSNhYUX41fkK4Xwy4UFEbq3Cdo/dBpR ZqwdOCqg5JfSW9dyYIRNMjwnVLuw8KhzqqZqiD74IP0vOQ4EN43WzK6XOkONzPBpOh5Y r9JQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=veMOlwm85HGnlMSTVN952J/Jqjc/7rvdCvDfPKEre0c=; b=HA2SmtGshnoP9rQPPeFf/H7OaidWEREm4lVN64y2mGS94x3X/0pgJ4KGbAuOSllwoe CE7uJPIAY+kUWS7tX5HUaThtcFoNARz6IT/zlQKasKcH7vTygE+phQBbtqUM2aGhmd8T GHG4CRsLnCvu6O+mSB3BhDFt6DkB65pTxIbMAgFNQkEuTWO1YSW6Qd+cl7MPLrXn7Ddz I/tjO/jE07Q+NDo508TFWCeSZV9DKa0NMs5R0OGUOVx2pvyw+4VRODHWCH+4iYFtl6kr GtlFS8+d3xCmXjMop6rJhUxfcFB9oAoOtPRnnsUfbITqXLCx5s2aM+wLdE7z7tLST8zL ZBkA== X-Gm-Message-State: AOAM532MofKMci3YiKrXNB7RCOyYvnotglLsPccaGExi9BTEECxGDUKe eHNywqrK6cnF99+UI+DTfjhKJXEkiTYLdizsr20bfA== X-Google-Smtp-Source: ABdhPJwCf3FmxgZrTisFeaRuj2pxBcn3CZA8Jzyk/0TkRmXwR5H+xd9VJWHscFXDHtkwCveC2Trx20irnwH9IVujNcM= X-Received: by 2002:a2e:a177:: with SMTP id u23mr1687459ljl.104.1599652679725; Wed, 09 Sep 2020 04:57:59 -0700 (PDT) MIME-Version: 1.0 References: <20200822163250.63664-1-paul@crapouillou.net> <20200822163250.63664-4-paul@crapouillou.net> In-Reply-To: <20200822163250.63664-4-paul@crapouillou.net> From: Linus Walleij Date: Wed, 9 Sep 2020 13:57:48 +0200 Message-ID: Subject: Re: [PATCH v2 3/6] drm: Add SPI DBI host driver To: Paul Cercueil Cc: Thierry Reding , Sam Ravnborg , David Airlie , Daniel Vetter , Rob Herring , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Noralf Tronnes , Laurent Pinchart , od@zcrc.me, "open list:DRM PANEL DRIVERS" , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , "linux-kernel@vger.kernel.org" , Mark Brown Content-Type: text/plain; charset="UTF-8" Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org Hi Paul, I looked a bit at this patch On Sat, Aug 22, 2020 at 6:33 PM Paul Cercueil wrote: > +config DRM_MIPI_DBI_SPI > + tristate "SPI host support for MIPI DBI" > + depends on DRM && OF && SPI I think you want to depend on SPI_HOST actually. > + struct gpio_desc *dc; This dc is very much undocumented, so I can only guess what it is for, please add some kerneldoc explaining what it is. I suppose it is in the DBI spec but I don't have it. > + gpiod_set_value_cansleep(dbi->dc, 0); Since it is optional I usually prefer to do it like this: if (dbi->dc) gpiod_set_value_cansleep(dbi->dc, 0); > + gpiod_set_value_cansleep(dbi->dc, 1); Since you drive this low when you assert it and high when you de-assert it, inverse this and mark the GPIO line as GPIO_ACTIVE_LOW in the device tree instead. > + dbi->dc = devm_gpiod_get_optional(dev, "dc", GPIOD_OUT_LOW); > + if (IS_ERR(dbi->dc)) { > + dev_err(dev, "Failed to get gpio 'dc'\n"); > + return PTR_ERR(dbi->dc); > + } Currently you are requesting the line asserted according to the above logic. Is that what you want? If you change the DT to GPIO_ACTIVE_LOW then this seems correct. But I am overall a bit curious about this "dc" thing. What is it really? It seems suspiciously similar to a SPI chip select, and then that is something that should be handled by the SPI core and set as cs-gpios in the device tree instead. It is certainly used exactly like a chip select as far as I can tell. Yours, Linus Walleij