From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4CED9171D2; Sun, 8 Jun 2025 12:55:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749387302; cv=none; b=dEyYS5+qztT/0wEHCzLl31ot9QIKjLVFzCb/MnaXahxnGg0dNFiaS6p7pfQpzBQTsXqZO1yTAKnCtS4XdpxfvjxW7h2lbr0t+7e/ZbYdTpnpjw2SYVb/FTHWF5+Jh4cHm9+fTb0swWII0sr5dOlhYGd3iKSxNCpL0Zv0LKtveCc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749387302; c=relaxed/simple; bh=4tn9f9ULQbJNgNb6yeBPXInYhXzFExWbdF4INVKpQ4A=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=V0chm6NxFFXolswHhyxPrOzZ0piV4rUXReoTZMsSh0n5ipxL2cI9Ff8NlWVuIVlOqv4EpcAHA0X1vFXuzzquKp7lclslVZYTHPJf5Y22vDcjJGWowsfr6OwTjJ4CrnECIf08IpiFMGGHvt1x7hY3IeQWqQrkwwfajD68jp0NrWo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NfgFXoTY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NfgFXoTY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5F595C4CEEF; Sun, 8 Jun 2025 12:55:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1749387301; bh=4tn9f9ULQbJNgNb6yeBPXInYhXzFExWbdF4INVKpQ4A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NfgFXoTYy61YL9NBUUW6rkjHJxgqPy7JrWG0q/sY+zZG1bBgDbWNkr0KbR7Ignzvk 075zblfJghRw7gvqRG1tL4I8wE5w7/1YyfbylnYqXA1nDi31BgRXVJeD9SH1/fB1Fd 0YUs/pKq9fVmxUTdLTzVxb04syc1n2igEXrzhIceyHs1TamyRSxjaISps2ig0U0Rj3 nWrlyVQbuEgiR9YWlUzxlCcr0uqLcKpqSdwjZWyIzXP+BaJ4e1KyPFkOLDi7z/vGdd nCn46yRhBSRETAPRkautzuXN557l4RovbzDohapFPcFKGmUqqNYcuS966RCsBvmJs+ ies30/wKpyQBA== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Thomas Gessler , Suraj Gupta , Folker Schwesinger , Vinod Koul , Sasha Levin , michal.simek@amd.com, jernej.skrabec@gmail.com, marex@denx.de, u.kleine-koenig@baylibre.com, krzysztof.kozlowski@linaro.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH AUTOSEL 6.14 07/10] dmaengine: xilinx_dma: Set dma_device directions Date: Sun, 8 Jun 2025 08:54:44 -0400 Message-Id: <20250608125447.933686-7-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250608125447.933686-1-sashal@kernel.org> References: <20250608125447.933686-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.14.10 Content-Transfer-Encoding: 8bit From: Thomas Gessler [ Upstream commit 7e01511443c30a55a5ae78d3debd46d4d872517e ] Coalesce the direction bits from the enabled TX and/or RX channels into the directions bit mask of dma_device. Without this mask set, dma_get_slave_caps() in the DMAEngine fails, which prevents the driver from being used with an IIO DMAEngine buffer. Signed-off-by: Thomas Gessler Reviewed-by: Suraj Gupta Tested-by: Folker Schwesinger Link: https://lore.kernel.org/r/20250507182101.909010-1-thomas.gessler@brueckmann-gmbh.de Signed-off-by: Vinod Koul Signed-off-by: Sasha Levin --- **YES** ## Analysis This commit should be backported to stable kernel trees because it fixes a critical functionality bug that prevents the Xilinx DMA driver from working with important subsystems. ### The Problem The commit addresses a fundamental issue where `dma_get_slave_caps()` fails when called on Xilinx DMA channels. The code change shows that the driver was not setting the `directions` field in the `dma_device` structure: ```c + xdev->common.directions |= chan->direction; ``` This single line fix accumulates the direction capabilities from individual channels (either `DMA_MEM_TO_DEV` or `DMA_DEV_TO_MEM`) into the device-level `directions` bitmask. ### Why This Qualifies for Backporting 1. **Fixes Important User-Facing Bug**: The commit message explicitly states this prevents the driver from being used with IIO DMAEngine buffers, which is a significant functional regression affecting real users. 2. **Small and Contained Fix**: The change is minimal - just one line of code that sets a required field during channel probe. This has extremely low risk of introducing regressions. 3. **Critical Subsystem Integration**: Without this fix, `dma_get_slave_caps()` calls fail with `-ENXIO`, breaking integration with any subsystem that queries DMA capabilities (like IIO). 4. **Clear Root Cause**: The fix directly addresses the root cause - the missing `directions` field that the DMAEngine core requires to be set. 5. **No Architectural Changes**: This doesn't introduce new features or change driver architecture; it simply provides required capability information that was missing. ### Comparison to Reference Commits This closely matches **Similar Commit #1** (marked YES) which also fixed a missing capability flag (`DMA_CYCLIC cap_mask bit`) that prevented proper DMA channel allocation. Both commits: - Fix missing capability declarations - Are small, single-line changes - Address integration failures with other subsystems - Have minimal regression risk The commit also mirrors **Similar Commit #2** (marked YES) which fixed incorrect struct usage in the same driver - both address functional correctness issues in the Xilinx DMA driver. ### Risk Assessment The risk is minimal because: - The change only affects the capability reporting mechanism - It doesn't modify any data paths or transfer logic - The direction values being OR'd together are already correctly set per-channel - Failure mode is obvious (capability queries will work instead of failing) This is a textbook example of a stable tree candidate: it fixes an important bug affecting real users with a minimal, low-risk change that doesn't introduce new functionality. drivers/dma/xilinx/xilinx_dma.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c index 108a7287f4cd0..99619da7fc09e 100644 --- a/drivers/dma/xilinx/xilinx_dma.c +++ b/drivers/dma/xilinx/xilinx_dma.c @@ -2908,6 +2908,8 @@ static int xilinx_dma_chan_probe(struct xilinx_dma_device *xdev, return -EINVAL; } + xdev->common.directions |= chan->direction; + /* Request the interrupt */ chan->irq = of_irq_get(node, chan->tdest); if (chan->irq < 0) -- 2.39.5