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 8C9FF49E143 for ; Fri, 25 Sep 2026 13:04:47 +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=1790341488; cv=none; b=UjFBiqhwYbwgLdjj3p0LQPxW+aVniBYPWUqvwqub+LNAg+lge0pYXbBmNsic9yuOFr7cxPWallVUR9W/saEDC+nwsBRDUXMqTl0uGPHmRhl/PdGQ7rVNCgAvnB11XJZwEP884f+nl7jRI18/vy3+yoTGNAsjzRf4lR1FRr8k+ho= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790341488; c=relaxed/simple; bh=WGSOc1cJBFuNR/LsR6uXNGa6Rv5l7gkj5jvs9DSrMd4=; h=From:Subject:To:Cc:In-Reply-To:References:Content-Type:Date: Message-Id; b=lVPx0rO1YCWq7jbY0qTY2LMxV4MB3aj13y/qenmlolwHeVGDNFyGeDwJ6QgYCzamPvO0+ltD5qve+kUR7NtuW/aDltSMbyR4yeukDbnAEsujmASEjtxPUnm5J2kgeX2cMStC70tBB8SfzYMrMEU2x/1dEFgiaSVk/igIjcTqibI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=RWRCtFgo; 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="RWRCtFgo" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01BA81F000FF; Fri, 25 Sep 2026 13:04:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790341487; bh=WGSOc1cJBFuNR/LsR6uXNGa6Rv5l7gkj5jvs9DSrMd4=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=RWRCtFgo9PifFgmTmzCzZv5mlS9athpXeEvKVIHlHRzn0+55HAi1ejUD5LDJca+Ae csRdTQAKo6FtaGYoZVLUF+mzACHIfGkzN4dysY00IHJ10KpfaK2E+8QNI2sliziLV8 Q3O1Ht3OXAFBpfgncyMdn/e2p3aDZ3rfurufK/107jZVP+/90iX263n4RfQHOy9LUW mG6Et0q5qURDCtAMzkuWxUkAhKNIn5lrIGsQYwvDoSN5YGTsiFsBk9Y4jEwL5RhqzW 8ptgJUYQEEDpH7+07CTOp23YsqJV9hHzgdoJi4jIW6pPGNRWlyODLc5SuuoYS+rHrA Yb3AZ3Eydtxng== From: sashiko-bot@kernel.org Subject: Re: [PATCH v2] 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: <20260925125443.168134-1-paultyson.mbewe@ziehl-abegg.de> References: <20260925125443.168134-1-paultyson.mbewe@ziehl-abegg.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Fri, 25 Sep 2026 13:04:46 +0000 Message-Id: <20260925130447.01BA81F000FF@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/20260925125443.1681= 34-1-paultyson.mbewe@ziehl-abegg.de?part=3D1