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 503D2C4332F for ; Fri, 18 Nov 2022 19:04:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242982AbiKRTES (ORCPT ); Fri, 18 Nov 2022 14:04:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34418 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S243008AbiKRTCs (ORCPT ); Fri, 18 Nov 2022 14:02:48 -0500 Received: from mail-wr1-x42e.google.com (mail-wr1-x42e.google.com [IPv6:2a00:1450:4864:20::42e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6FCB554B10; Fri, 18 Nov 2022 11:02:36 -0800 (PST) Received: by mail-wr1-x42e.google.com with SMTP id g12so10650823wrs.10; Fri, 18 Nov 2022 11:02:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:sender:from:to:cc:subject:date:message-id:reply-to; bh=E5Ey+SWUGHe54inhYQO4Q9IAek2nNg4LJ02tyTCqBBc=; b=muB+SifbTgI90sosGYp1Rdn9323oxvY/zKHPXxKDBsUaWLb+RDwNiQr346MUdyu7lC Gucft/tc7JBy/sxc44JyFyG2pL7UhNO5tik1/CaLmaBOOQFGFjDrt0rB71jm5h/WW4VN QNg3RKWX0yEJPqu7dLKG9Oz+By3cLCmQAhF8eLI7rFfy2yycAgWBMaPK9DwHZxe3OMnd Ij6RcFnNjlBq625Wwun3KE3WP0OiqrZKmC86roZKUid0EjoAuLba4qAFT4oNMBoenwt7 RAsO4KMWBw0qoEuZZ66LqXSWOJp+pEvUrWX9/krmnj7hktPOkvvrhpqfLLg8YTYrYNQX vy1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:sender:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=E5Ey+SWUGHe54inhYQO4Q9IAek2nNg4LJ02tyTCqBBc=; b=sDSkueVDN3ph5p4ZSCGqrDF7+P/VU6s5HeQV/gjVCACLtOQjrhh8ZgkzNVynSOjzpR wv4+iRKrbSWuY2R4RprFk5sKxpI//rPCFfq7B1nSn1vsG894vACQQWqkbHVZBtwXARTZ mDMKuL1I9cuyhfwHHkjPXdgcdysc+eRl7LBZr26llyKf5vZEUSFou2ETQKOzgb+nKLTL pBSfG++KwtratfWv40a5qojaaghAbbp7okkgSCJFWoNKKc+j4l0aXzrkFlujFMEuN6Ho MXIEBvuFjczONl3FXVuznOmSgomYaXvIhlVBB8hOxcja2Wnr17MeIpqcSe+abz3Abw// 093w== X-Gm-Message-State: ANoB5plyHq9hUPPSW6mirs+cLb+tf2kKwx1+JHKYkqCkThIH0rRhlrdI FfPc28/fYblO2A+ULiYQrYhlBXp7fQtgsDKl X-Google-Smtp-Source: AA0mqf6w/1xAUqgYy2FX3lJHlg67dGBf2UYoc+mhcExG80QMtV/cbLJw50V7xfWynisTt8PVUp27yg== X-Received: by 2002:a05:6000:114f:b0:241:c80c:5f54 with SMTP id d15-20020a056000114f00b00241c80c5f54mr476592wrx.15.1668798154591; Fri, 18 Nov 2022 11:02:34 -0800 (PST) Received: from ?IPV6:2a0e:41a:894f:0:6f8e:6bf6:725c:d7d5? ([2a0e:41a:894f:0:6f8e:6bf6:725c:d7d5]) by smtp.gmail.com with ESMTPSA id u16-20020a05600c19d000b003cf37c5ddc0sm5775361wmq.22.2022.11.18.11.02.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Nov 2022 11:02:33 -0800 (PST) Sender: Carlo Caione From: Carlo Caione X-Google-Original-From: Carlo Caione Message-ID: <8a3bdd84-2789-1b42-976f-2843320750b6@baylibre.com> Date: Fri, 18 Nov 2022 20:02:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.2 Subject: Re: [PATCH 2/3] drm/tiny: ili9486: Do not assume 8-bit only SPI controllers Content-Language: en-US To: Mark Brown Cc: Kamlesh Gurudasani , Neil Armstrong , Jerome Brunet , David Airlie , Martin Blumenstingl , Kevin Hilman , Daniel Vetter , linux-arm-kernel@lists.infradead.org, linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, dri-devel@lists.freedesktop.org References: <20221116-s905x_spi_ili9486-v1-0-630401cb62d5@baylibre.com> <20221116-s905x_spi_ili9486-v1-2-630401cb62d5@baylibre.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/11/2022 16:44, Mark Brown wrote: >> The problem arrives when your controller does support 16-bits, so >> your data is not swapped, but you still put the data on the bus >> with 8-bit transfers. > > Why would you need to use 8 bit transfers if the controller supports > 16 bits? No idea why this driver is forcing 8-bit transfers when the controller supports 16-bits (this is what this patch is fixing). My theory is that this driver was written with the Raspberry Pi HATs in mind and (AFAICT) the RPi has an 8-bit only SPI controller so the driver author didn't bother with anything different. -- Carlo Caione