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 gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 53D59F45A0D for ; Fri, 10 Apr 2026 21:01:42 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9206B10E1C3; Fri, 10 Apr 2026 21:01:41 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="JXTTppZX"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 2F33010E1C3 for ; Fri, 10 Apr 2026 21:01:40 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 0A43460141; Fri, 10 Apr 2026 21:01:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 15C6BC19424; Fri, 10 Apr 2026 21:01:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775854898; bh=8k+cK41OdLbgiT4F2k1zDjLX7TALCLcSSuKKXuBD5b0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JXTTppZXN+vGmdnk2DXTuCGh1voIkYp9YeyZ5p3j2xv7T9htCXGGteKGaDSydEDRt eSJweeepxWIhcwsawv2pX61JdAPCdNZW4Sk/Z+fL1frDE92WQkAZL4n3XQ91I//bIe c4nNwR+Ta2Prra1N8RHrMtMixyGTe1fbG9qvaFHDQCZqr+tOebuJcnAyoG5Yh//g1m 5U/VMXemnaVONazS2wcmdGOnOBR7XH73+PsznIuBo9PUNgPhv83ucaM3PR8ad582vj Hnm5tlIE/eq5+zWthQuCd3yk+B3T4o8Kwc9c7cqQDtnrbc50plLiIOgudNrv7OtJQJ C5p9QDil4hnJw== Date: Fri, 10 Apr 2026 23:01:34 +0200 From: Andi Shyti To: Aniket Randive Cc: mukesh.savaliya@oss.qualcomm.com, viken.dadhaniya@oss.qualcomm.com, sumit.semwal@linaro.org, christian.koenig@amd.com, linux-i2c@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, naresh.maramaina@oss.qualcomm.com Subject: Re: [PATCH V4] i2c: qcom-geni: Avoid extra TX DMA TRE for single read message in GPI mode Message-ID: References: <20260410101949.2315058-1-aniket.randive@oss.qualcomm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260410101949.2315058-1-aniket.randive@oss.qualcomm.com> X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi Aniket, On Fri, Apr 10, 2026 at 03:49:49PM +0530, Aniket Randive wrote: > In GPI mode, the I2C GENI driver programs an extra TX DMA transfer > descriptor (TRE) on the TX channel when handling a single read message. > This results in an unintended write phase being issued on the I2C bus, > even though a read transaction does not require any TX data. > > For a single-byte read, the correct hardware sequence consists of the > CONFIG and GO commands followed by a single RX DMA TRE. Programming an > additional TX DMA TRE is redundant, causes unnecessary DMA buffer > mapping on the TX channel, and may lead to incorrect bus behavior. > > Update the transfer logic to avoid programming a TX DMA TRE for single > read messages in GPI mode. > > Co-developed-by: Maramaina Naresh > Signed-off-by: Maramaina Naresh > Signed-off-by: Aniket Randive merged to i2c/i2c-host. Thank you and thanks Mukesh for the review. Andi