From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1EC6533E367 for ; Tue, 8 Sep 2026 06:25:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788848742; cv=none; b=g1UQ3tUYetDtfr3K6S+PcJd2TJQlwfKmjhH0WD/vwTUbmwUdpIEwDOKED/YdMeIrq04xj1tCqyPto+Ze/UazqWuIShztW97aN6yHkizI+fXfGKMOLcybpbO2SN7gyvyMk9Xidn8jstaqlK+rIT/cgztZjuozn/4Dh/Lvh2TgQNQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788848742; c=relaxed/simple; bh=u8vTQBBDKI9QDM3bfM4fcJTC2oUv0buHBN0sDbg880w=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=splUKFLDQOU0T4TE7o8qPSqeh4sq7B7oCKsqnMhEycRcgyESP34T9KRL/FXq7Ic6gjCr7J+SLAdtHluIcnIqF2ytEjutkTjD8IuRJ8fz3/rmSr/qw2hoUjR7M4ZR9omXT9jqLVfX837SILsSArrOO5D2MQwTD0ArQt8wOYPvhOk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EdP6jHe0; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EdP6jHe0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 81E381F00A3D; Tue, 8 Sep 2026 06:25:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788848740; bh=u8vTQBBDKI9QDM3bfM4fcJTC2oUv0buHBN0sDbg880w=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=EdP6jHe043IPIsKsHdSiGj0CxZTikcx7KgL+jMsUwWCwyoFvGP2AkmjvlFnskmDKi wWHOJGXryhQY80ig92uR3KzgvI8AaLyFyjZ7zBuAQDBmwzV48H+8AZUXp0Ulm3xBfy iJ+/fgkFo9TmTkL6QbBU0MHolaYLB8gZU85XUgJA++oV2E+ngJEM1cJuWeGSemyRW1 nP1cZ27lOt1HlFa5SgCcapA/0zIkg6UIDhOmefE76WjcA6oi0miQX5brBg4xRv5Tsh QfGMuudNP0msn63sptghdO8cGTe/jKdKYp+dgkbJT/AVbv7kAcyqvUnv58pL7GhuV4 3TUO8/ur/btSg== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2] pci: designware: Set DMA_BYPASS bit in outbound IATU CTRL2 register Reply-To: sashiko-reviews@lists.linux.dev To: "Sumit Kumar" Cc: linux-pci@vger.kernel.org In-Reply-To: <20260908-dma_bypass-v2-1-c3c81d408c0c@oss.qualcomm.com> References: <20260908-dma_bypass-v2-1-c3c81d408c0c@oss.qualcomm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Tue, 08 Sep 2026 06:25:40 +0000 Message-Id: <20260908062540.81E381F00A3D@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > An outbound iATU region matches any local (AXI/application-side) > address that falls within its Base/Limit window and rewrites it to > the PCIe-side address programmed in that region's Target Address > Registers before the transaction goes out on the link. This matching > does not distinguish CPU-initiated transactions from ones issued by > the internal DMA engine (eDMA/HDMA). >=20 > Example: outbound region 0 is programmed with Base/Limit covering > local addresses 0x8000_0000-0x8000_0FFF and Target 0x1_0000_0000, for > CPU-initiated accesses. The DMA engine is later given a descriptor > whose destination is the host address 0x8000_0080, which happens to > fall inside region 0's Base/Limit range. The iATU matches the DMA > transaction against region 0 too and rewrites it to 0x1_0000_0080 > instead of passing 0x8000_0080 through unchanged. The transaction > then lands on the wrong host address, causing data corruption or an > IOMMU fault when the rewritten address has no valid mapping. >=20 > Set the DMA_BYPASS bit (bit 27) in PCIE_ATU_REGION_CTRL2 when > programming outbound iATU regions so only CPU/AXI-initiated > transactions are matched against the region; DMA engine transactions > bypass the translation and go out on the PCIe link with their > original address. >=20 > Signed-off-by: Sumit Kumar Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260908-dma_bypass= -v2-1-c3c81d408c0c@oss.qualcomm.com?part=3D1