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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 92CD2C54FB3 for ; Mon, 2 Jun 2025 01:03:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=foN3wx/oF4Wkrf39+ThD1ZlqWStiAURx8dJZzAexlmY=; b=ImNhgm2hh1E/1cc+dlb3BHXAjW bAsLzr3v7URqhtZkxkFZ2FkuUnDCjUNp4vHCCJ/r04RiQyAI03fBTWkVwrV9nNKHj5SYnVfHiQQqQ zyiDKpd5Za2w+iPluotvP98uguy5vcIwP2vfqfEACMP78SeFkyTqA4OIdfJKFesN1CBALqGT2OhGT jTCqKYaBCIccsK+crVQBal7Joq1deamxG75Tx86mQNmEURWZIVQCZS60LQFojysi2Rsk9K2LKft9T G9wxT62nG9MiEAHnhhD4Si+bcr5ZGV4hKiWT4cLT5aIppZ1bKzHmIh2AbivN5hylzB8JsnRXlTCdz Z4rQjV4Q==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uLta7-00000006Q6b-1aRh; Mon, 02 Jun 2025 01:03:15 +0000 Received: from nyc.source.kernel.org ([147.75.193.91]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uLsJD-000000069VG-1bni for linux-arm-kernel@lists.infradead.org; Sun, 01 Jun 2025 23:41:44 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by nyc.source.kernel.org (Postfix) with ESMTP id B76FDA4FB59; Sun, 1 Jun 2025 23:41:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 187ABC4CEE7; Sun, 1 Jun 2025 23:41:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1748821302; bh=A48W80d/OvYkJUwQnKQg9w4xhc8rbidgZOgmvwELG1g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CM0NVZt2jVbtGaj//AM2Dv03XlH2mCsEMVHEoTU1xPoo5uBrvwE0wXgaJW7At3bJv ztacx3NfIU11MUaictjzYT9+gS9w9jEkyjZFB63zZTX0LpViKwWs2kaDyV6Eui4lsC ChXcbENEVj0xZnQXR7pWMHrihIO3KjqZ1PLXTJElH2AsdyW4XUYFJlrhT3Fv6C7Z5S 3ky+EciOaJjh7qyRyilzbtRocR2/7qe037gHIssO62ejU2a5bhpDTAOEraCV/OSfW2 mcQcC0jiXVlzFbCMblNYaF51aA+RSzFclbTsf7l64NM5a2P6d7ukXvIPYG/2H985Av YMM2b7uwmuzIg== From: Sasha Levin To: patches@lists.linux.dev, stable@vger.kernel.org Cc: Wentao Liang , Hans Verkuil , Sasha Levin , s.nawrocki@samsung.com, mchehab@kernel.org, krzk@kernel.org, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH AUTOSEL 6.1 36/58] media: platform: exynos4-is: Add hardware sync wait to fimc_is_hw_change_mode() Date: Sun, 1 Jun 2025 19:39:49 -0400 Message-Id: <20250601234012.3516352-36-sashal@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250601234012.3516352-1-sashal@kernel.org> References: <20250601234012.3516352-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.140 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250601_164143_549932_5F15393E X-CRM114-Status: GOOD ( 13.78 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org From: Wentao Liang [ Upstream commit bd9f6ce7d512fa21249415c16af801a4ed5d97b6 ] In fimc_is_hw_change_mode(), the function changes camera modes without waiting for hardware completion, risking corrupted data or system hangs if subsequent operations proceed before the hardware is ready. Add fimc_is_hw_wait_intmsr0_intmsd0() after mode configuration, ensuring hardware state synchronization and stable interrupt handling. Signed-off-by: Wentao Liang Signed-off-by: Hans Verkuil Signed-off-by: Sasha Levin --- Based on my analysis of the commit and examination of the kernel code, here is my assessment: **YES** This commit should be backported to stable kernel trees for the following reasons: ## Analysis of the Code Change The commit adds a single line `fimc_is_hw_wait_intmsr0_intmsd0(is);` at line 167 in the `fimc_is_hw_change_mode()` function in `drivers/media/platform/samsung/exynos4-is/fimc-is-regs.c`. ## Why This Should Be Backported 1. **Clear Bug Fix**: The commit message explicitly states this fixes a race condition where "the function changes camera modes without waiting for hardware completion, risking corrupted data or system hangs if subsequent operations proceed before the hardware is ready." This is a classic hardware synchronization bug. 2. **Consistent Pattern**: Examining the surrounding code shows that ALL other similar hardware control functions (`fimc_is_hw_get_setfile_addr()`, `fimc_is_hw_load_setfile()`, `fimc_is_hw_stream_on()`, `fimc_is_hw_stream_off()`) already call `fimc_is_hw_wait_intmsr0_intmsd0()` before writing to hardware registers. The `fimc_is_hw_change_mode()` function was the only outlier missing this synchronization. 3. **Minimal and Safe**: The change is extremely small (one line) and uses an existing, well-tested synchronization primitive. The `fimc_is_hw_wait_intmsr0_intmsd0()` function implements a timeout-based wait with proper error handling. 4. **Critical Subsystem**: This affects camera hardware control in Samsung Exynos4 SoCs. Hardware synchronization issues in camera drivers can cause: - System hangs (as mentioned in commit message) - Data corruption - Unpredictable hardware state 5. **Runtime Safety**: The wait function has built-in timeout protection (2000 iterations with 1μs delay each), so it cannot cause infinite hangs even if hardware fails. 6. **Follows Hardware Protocol**: The pattern clearly shows the proper hardware protocol is: wait for ready state → write command → trigger interrupt. The missing wait was a protocol violation. ## Comparison with Historical References Looking at the provided similar commits marked "NO" for backporting, they were all: - Documentation/binding changes (commits #1, #2) - Code cleanup/feature removal (commit #3) - Architecture changes (commit #4) The one commit marked "YES" (commit #5) was a simple bug fix correcting a return value check, very similar in nature to this synchronization fix. This commit fits the stable tree criteria perfectly: it's a small, contained bug fix addressing a real hardware synchronization issue that could cause system instability, with minimal risk of regression. drivers/media/platform/samsung/exynos4-is/fimc-is-regs.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/media/platform/samsung/exynos4-is/fimc-is-regs.c b/drivers/media/platform/samsung/exynos4-is/fimc-is-regs.c index 366e6393817d2..5f9c44e825a5f 100644 --- a/drivers/media/platform/samsung/exynos4-is/fimc-is-regs.c +++ b/drivers/media/platform/samsung/exynos4-is/fimc-is-regs.c @@ -164,6 +164,7 @@ int fimc_is_hw_change_mode(struct fimc_is *is) if (WARN_ON(is->config_index >= ARRAY_SIZE(cmd))) return -EINVAL; + fimc_is_hw_wait_intmsr0_intmsd0(is); mcuctl_write(cmd[is->config_index], is, MCUCTL_REG_ISSR(0)); mcuctl_write(is->sensor_index, is, MCUCTL_REG_ISSR(1)); mcuctl_write(is->setfile.sub_index, is, MCUCTL_REG_ISSR(2)); -- 2.39.5