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 BDE1036607D; Thu, 30 Jul 2026 15:52:38 +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=1785426759; cv=none; b=Eso0DlewY0dnQ8OnwF2M73HJ9TyPSPtZVG+TsNxgExYnMRmDtNOele1pu3yHfD220a/Qve0elYj3gHcINLWJZEKnM0unks4ZUvCmZhE6leW9EWsJKgWKp8fxEGol7FNsfxiZ6OAKvKWVMfHrWKIu/03lPRB+423yWOFG/AiIcBs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785426759; c=relaxed/simple; bh=y+nwKucfT+WesDR3MYW36S0GCfd6esQRaphhnKWrXtQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=P1/BvNouanrisKLY2dMGVHR+WxJTrR5DD/au9b4xnXOv/4QL/AhMI3sq82ibDu/OOt12Ro+sdfRjqVmJJTiB81MmN/Lk7+qSHm72RvU+Ah3J6MH7lHhxbhQN6eGJ8/eBB+yUD29NBMb2fVQIHO00sGG2t/6AB/s5JUeedc1qV+c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xq+H2Ddm; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xq+H2Ddm" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 2A7B91F000E9; Thu, 30 Jul 2026 15:52:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785426758; bh=cq7WgNMyGpLUN1VaYkC/sevZ7HzLy7LEoQW4PDwUKcs=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xq+H2DdmCbsRsPgI/LS7iHb5TALIMlea5NDrovlOmUAuJ+aHJ4HqNNHJnYB3KvHgk Mh2/diBle/DD2AlzWO9gFHs95v/bfnXpUhaULpOYsZmEcs7iMwhyGO/4n3Xu9lqmB3 0Xjdz33e6el9qOsAYr4Kn2btNoTzPiexPXbgUY04= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Vincent Jardin , Oleksij Rempel , Carlos Song , Stefan Eichenberger , Andi Shyti , Sasha Levin Subject: [PATCH 6.12 533/602] i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) Date: Thu, 30 Jul 2026 16:15:25 +0200 Message-ID: <20260730141447.217887865@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141435.976815864@linuxfoundation.org> References: <20260730141435.976815864@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vincent Jardin [ Upstream commit cb2fc37857693b55909fb77dc2c87cfbc1cdc476 ] SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic (polling) path rejects it as -EPROTO. Worse, it returns without a NACK+STOP: the next receive cycle has already started, so the target keeps holding SDA and the bus stays stuck until a power cycle for this i2c controller. Reading I2DR to obtain the count likewise arms the next byte on the count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly and left the bus held. Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so the existing last-byte handling emits STOP; the dummy byte is discarded. A count of 0 is a valid empty block read; a count above I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus has been released. The interrupt-driven path has the same flaw from a later commit and is fixed separately, as it carries a different Fixes: tag and stable range. Fixes: 8e8782c71595 ("i2c: imx: add SMBus block read support") Signed-off-by: Vincent Jardin Cc: # v3.16+ Acked-by: Oleksij Rempel Acked-by: Carlos Song Reviewed-by: Stefan Eichenberger Signed-off-by: Andi Shyti Link: https://lore.kernel.org/r/20260713-for-upstream-i2c-lx2160-fix-v1-v3-1-073ac9e103a5@free.fr Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/i2c/busses/i2c-imx.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) --- a/drivers/i2c/busses/i2c-imx.c +++ b/drivers/i2c/busses/i2c-imx.c @@ -1180,6 +1180,7 @@ static int i2c_imx_read(struct imx_i2c_s int i, result; unsigned int temp; int block_data = msgs->flags & I2C_M_RECV_LEN; + int block_err = 0; result = i2c_imx_prepare_read(i2c_imx, msgs, atomic, false); if (result) @@ -1201,8 +1202,20 @@ static int i2c_imx_read(struct imx_i2c_s */ if ((!i) && block_data) { len = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); - if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX)) - return -EPROTO; + if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX)) { + /* + * SMBus 3.1 6.5.7: support count byte of 0. + * I2C_SMBUS_BLOCK_MAX case should not hold the SDA either. + */ + if (len > I2C_SMBUS_BLOCK_MAX) + block_err = -EPROTO; + temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR); + temp |= I2CR_TXAK; + imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR); + msgs->buf[0] = 0; + msgs->len = 2; + continue; + } dev_dbg(&i2c_imx->adapter.dev, "<%s> read length: 0x%X\n", __func__, len); @@ -1250,7 +1263,7 @@ static int i2c_imx_read(struct imx_i2c_s "<%s> read byte: B%d=0x%X\n", __func__, i, msgs->buf[i]); } - return 0; + return block_err; } static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,