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 D101D449B1C; Thu, 30 Jul 2026 16:16:56 +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=1785428219; cv=none; b=Zo7+miw31dOjiPn/0ZYaSE9nQUiigz92xAr87KE9+XrN/F6/bKoE0BCxmfM5wbpRMv8xF5PXzjHR4O5T33oHZiJslyO+cPyknI6ULCDD0/Xt8ICX9TF9ZEzj1qp41jBOGCUoMNzQg72bIK532o/bam7vsfjQXP2XX2spDw1xWqo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785428219; c=relaxed/simple; bh=CeKIjuFjfvgXFoRW98uaovtMsIsyWyjgC53dAdnpiPc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YB51vqdm1OdxnExsxJ+Pqt4thRsYWyxNCnDHQGJKVzF/oitSuKOqGxoMaGOUYmkHopCI2cEslGdT6Dt1pJoteXdzmhsTucXL0LNxM3Tw0Y/BAGUZt5v9vEnZHI5oldxbmHNwnV+2vxQfTMBYPPjv1gvtF2KSD9ABF3toUD5MgWY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=aGQ5BJnc; 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="aGQ5BJnc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9BD7F1F00A3F; Thu, 30 Jul 2026 16:16:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1785428216; bh=I/QJudmJu6pSkaTtaqcWWyaZT0fMbCYcMXSmiN1eros=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=aGQ5BJncYtBetrfviU4Xhr8Yp0gpWzQtfokdI3jWwgIOwNsUDs8crFfP04+Hdt5fL L+7g8OAuzkarapTQQUztU5AF0OPNJlRi+qry7A3S8o/kZhpDLNIDsYfGlSoIRUU2Gz xrftGosKWR5hTIjTkRS8YeNZsRsHE1FgewpBr6Qs= 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 6.6 444/484] i2c: imx: fix locked bus on SMBus block-read of 0 (atomic) Date: Thu, 30 Jul 2026 16:15:41 +0200 Message-ID: <20260730141433.126591020@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260730141423.392222816@linuxfoundation.org> References: <20260730141423.392222816@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 6.6-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 @@ -1184,6 +1184,7 @@ 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) @@ -1205,8 +1206,20 @@ 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); @@ -1254,7 +1267,7 @@ 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,