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 9F3FA13A258 for ; Sat, 10 Oct 2026 19:49:14 +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=1791661756; cv=none; b=qhUafCHRWF9YUsB/ww2EQElHhterET3TJ8RW9l3v6edaS8oadXZLeRrOmMxreS+nwIdOugpMZyldkjCcmAyqXha/g8AUADjKiPkZjTGE9Xusjb87WvgSvxM/jI4tdQeMCw49iKwK63/oHBTQRdT1iCBHlJgGeVyZEcad/uqPfkU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791661756; c=relaxed/simple; bh=eh9OXsNMS9mRtIC5UkHi+mJ0+6xBIhd7bLz7ifIhkng=; h=Message-ID:From:Subject:To:Cc:In-Reply-To:References:Content-Type: Date; b=TaILCCu6Jxja9eo1qoOSmAR2o5Fe085o08p+xI+REAVKCzMDUWKRSsMpI+XO2K9FRF+m7epUMUzcVVJ363XUQHeh1w1fkM2Ys+4yYBg5FVDyXZbQHnTB0IAE8146DiJPALJ78Aftlcho4zzTpPukOPZhaAWl3vIszdoG8HTHS1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T5KVjFgy; 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="T5KVjFgy" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3CAD71F000FF; Sat, 10 Oct 2026 19:49:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791661754; bh=kSEKbPXykgUO8WZssg1XEd7Gh21dWHCpeUUUcchJpVk=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=T5KVjFgyQs7QT6j6L5WvS1aoGlbRwT9uxS7Ta4xFolHwnZtnjjke360pWqGdJ9o5E 0Mnb40Zdf+agoL9V/ARMb3Icg8Zzlw7rC/+AONgi2BhKuQXMs4+YKnU5R/DrLf5WpU OY4mBUamplRpqO4HKY25PtAddYCg6+0yA3PVJHsF29sKm1q2IjC4OizUz4FLdbBgyk hsjhEEFQ6WWeEgqYWSVtIa6JWh0hjfhEKyIEVQajSHYkyi6+5Q9NBPDGR71+wUyvij z25zXD6HLBgeYoYYu2lIeyIkbg2i+BT11d6e+WyOaZRU7v4Mn9lNPpFYqkF0+HlRpS jg/53I/7n3G0Q== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v1 1/1] Revert "serial: 8250_port: Drop duplicate NULL check" Reply-To: sashiko-reviews@lists.linux.dev To: "Ferry Toth" Cc: linux-serial@vger.kernel.org In-Reply-To: <20261010193755.187706-2-ftoth@exalondelft.nl> References: <20261010193755.187706-2-ftoth@exalondelft.nl> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sat, 10 Oct 2026 19:49:13 +0000 Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > This reverts commit 7885af04df6e4efd72910200c1bfc079d61202e4. >=20 > Commit 7885af04df6e ("serial: 8250_port: Drop duplicate NULL check") > added `up->dma =3D NULL;` to serial8250_release_dma(), with the stated > intent of making sure DMA would not be used again after release. >=20 > However, up->dma is assigned once at probe time. serial8250_do_startup() > only calls serial8250_request_dma() when up->dma is non-NULL, so after > the first close the pointer stays NULL and DMA is never re-acquired. >=20 > On Intel Tangier (Edison) with HSU DMA this causes a regression: the > first port open uses TX DMA, the second and later opens transmit in PIO > mode, producing 64-byte FIFO bursts with ~50us gaps between them. >=20 > Fixes: 7885af04df6e ("serial: 8250_port: Drop duplicate NULL check") > Cc: stable@vger.kernel.org > Signed-off-by: Ferry Toth Sashiko has reviewed this patch and found no issues. It looks great! --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261010193755.1877= 06-2-ftoth@exalondelft.nl?part=3D1