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 2AF8137C0FE for ; Mon, 28 Sep 2026 09:03:53 +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=1790586235; cv=none; b=WFHEM64zOjmjJBGSqJ1D1ClU1eu1WetH5Ab4KBSweL4VDZYl6OHpGROHrmZjWLeLZy/1vuIZ2e8vBQLHrN1pOoy5jTaO/UyOJaUQs23p8oJZoy2wzehAKF1Q3rO4vJfU6rc2T+71gutJNYjP3pCOvFe9sXWbUKd/XZgtjC8RSJg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790586235; c=relaxed/simple; bh=sjuNU8/nN1UM22m2rgYHjnqMLe1ahYmjPQoYWahYF+g=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=ERc81FEM/kfxBcPLR8+lycm6kH3qWbBPbMCq3/ywYDfEZHL26wpgAZF1vkK6FT0j0OicK+IEK45L8sO82Zy3Lz7WKdbkfS7XWB7Pk6Whdx4VZDQmJoEWwxX8MZFcmE92mLk/5GebVyrwOtaSgQzpV0mIB8uPISS+uXzVV/4Jwc0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eFj4A3p+; 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="eFj4A3p+" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8A32C1F000FF; Mon, 28 Sep 2026 09:03:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790586233; bh=sjuNU8/nN1UM22m2rgYHjnqMLe1ahYmjPQoYWahYF+g=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=eFj4A3p+GcPXUsWNmw3sSGBOzYF7GKd/CIQfzWz/iL2N3SKIY4/GP9FqmAbyjmWIy f9ZxRa9BpuPy9CFPtM4AMCahBZvmNb4WW2wYAjzhPu1JRgqkAqsyZr5JDfBi6gXbyx bo3pTeCgMG1N1nIUdglJwS+cOfz1EtLXO5BdClcL8NlSVwF4Wf8FpzQLODSVeNP31D 4vh1XKe/hj21jEatBm3jLLB7BXnhMF34kUh5G8Al34gg5iDFLnkfGEI3vXYV0yFoif Da0e1d7LTt2TePJaGM5hGO6i35+LtM7Og1r1MGthIPkpR99HJmPyG0+WYVFywDG2/P MH6G018Zo895Q== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2 RESEND] serial: sc16is7xx: fix TX gap caused by kfifo circular buffer wrap-around Reply-To: sashiko-reviews@lists.linux.dev To: "Paul Mbewe" Cc: linux-serial@vger.kernel.org In-Reply-To: <20260928085559.3341419-1-paultyson.mbewe@ziehl-abegg.de> References: <20260928085559.3341419-1-paultyson.mbewe@ziehl-abegg.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Mon, 28 Sep 2026 09:03:53 +0000 Message-Id: <20260928090353.8A32C1F000FF@smtp.kernel.org> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > kfifo_out_linear_ptr() returns only one contiguous linear segment of the > xmit kfifo. When transmit data wraps around the end of the kfifo, only > the first segment up to the buffer end is sent. The remaining data at > the start of the kfifo is not sent until the next TX interrupt fires, > resulting in a visible mid-frame TX gap on the wire. >=20 > The resulting gap is unintended: data remains queued in the xmit kfifo, > but the hardware TX FIFO drains empty before the remaining segment is > sent. Such gaps can break timing-sensitive serial protocols such as > Modbus RTU. >=20 > Modbus RTU requires a message to be transmitted as a continuous stream. > For baud rates above 19200, the Modbus Serial Line guide recommends a > fixed 750 us inter-character timeout. On the tested 115200-baud system, > oscilloscope measurements showed mid-frame gaps exceeding that value. > [ ... ] > Cc: stable@vger.kernel.org > Reported-by: Tobias Gannert > Reviewed-by: Joachim Knorr > Link: https://lore.kernel.org/linux-serial/20260623112225.82386-2-paultys= on.mbewe@ziehl-abegg.de/ > Signed-off-by: Paul Mbewe Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20260928085559.3341= 419-1-paultyson.mbewe@ziehl-abegg.de?part=3D1