From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754112AbbIJAXq (ORCPT ); Wed, 9 Sep 2015 20:23:46 -0400 Received: from mailout1.w1.samsung.com ([210.118.77.11]:14406 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753835AbbIJAXm (ORCPT ); Wed, 9 Sep 2015 20:23:42 -0400 X-AuditID: cbfec7f4-f79c56d0000012ee-96-55f0cd8bc8a0 Subject: Re: [PATCH 0/3] serial: samsung: Fix UART status handling and other fixes To: Robert Baldyga , gregkh@linuxfoundation.org References: <1441705127-24125-1-git-send-email-r.baldyga@samsung.com> <55EF7395.2000702@samsung.com> <55EFF898.7060205@samsung.com> Cc: jslaby@suse.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, m.szyprowski@samsung.com From: Krzysztof Kozlowski Message-id: <55F0CD8B.8080403@samsung.com> Date: Thu, 10 Sep 2015 09:23:39 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.2.0 MIME-version: 1.0 In-reply-to: <55EFF898.7060205@samsung.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFrrMLMWRmVeSWpSXmKPExsVy+t/xK7rdZz+EGmzr1LdoXryezWLKhg9M Fq9fGFpc3jWHzeLM4l52i7VH7rJbPDi8k92B3WP/3DXsHn1bVjF6rN9ylcXj8ya5AJYoLpuU 1JzMstQifbsEroyu1wtYCk7yVJzcztnA2MzVxcjBISFgInFvDm8XIyeQKSZx4d56ti5GLg4h gaWMEssP7WSBcL4wSsw4fZ8ZpEpYIERiyroz7CC2iICbxKJ/d6E6WhklVu9YyQqSYBbIlvjY vIwFxGYTMJbYvHwJG4jNK6Al0fjgJiOIzSKgKjHpfwtYvahAhMSps2+hagQlfky+B9bLKaAt sfDvYyaQS5kF9CTuX9SCGC8vsXnNW+YJjAKzkHTMQqiahaRqASPzKkbR1NLkguKk9FxDveLE 3OLSvHS95PzcTYyQoP6yg3HxMatDjAIcjEo8vBNa3ocKsSaWFVfmHmKU4GBWEuFN2/4hVIg3 JbGyKrUoP76oNCe1+BCjNAeLkjjv3F3vQ4QE0hNLUrNTUwtSi2CyTBycUg2MOUsUQ17t5X9e dirTP2nSY3OJrVuPn1lWuTnMaefsLTyuZZ2zds/bv/5JefLRP7Pi32k2SCnFFk/fF1fwX7au +4K8Ya8U9+zzSQor4xdxfjr6zGvTxNJlPJUNxj2rZSZNW2hbMTNhy46mn3O/bdCfWqH0jeOH U5Z37e6lmnfblKeLV6Su+PPxlRJLcUaioRZzUXEiAHDm4nVmAgAA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.09.2015 18:15, Robert Baldyga wrote: > On 09/09/2015 01:47 AM, Krzysztof Kozlowski wrote: >> On 08.09.2015 18:38, Robert Baldyga wrote: >>> Hello, >>> >>> This patch set contains three patches: two minor fixes and one quite >>> important bugfix enabling UART status handling in DMA mode, which was >>> missing so far. It enables, among others, 'break' contition handling, >>> which is necessary if we want to use Magic SysRq. So this patch fixes >>> Magic SysRq handling for serial consoles using UART in DMA mode, >> >> Is it even worth using UART for serial console in DMA mode? How many >> benefits it brings? Anyone measured real data? >> >> The patch which enabled DMA for all serial ports on Exynos4 uncovered >> some issues. That is one benefit... but was it worth it? > > Well, UART in DMA mode should work at least as good as in PIO, so there > is nothing wrong in having serial console configured in DMA. Sure, it > rather barely reduces number of interrupts while used as typical serial > console, but in some cases (eg. using zmodem) it can be more profitable. That's some reason... and mentioned earlier testing of DMA which uncovered some interesting issues. :) > > To be honest, I have no strong feeling about that. I've decided to > utilize new possibility opened by introducing DMA mode in serial driver, > so I've send patch enabling it for each port on Exynos4. But if it > turned out to be unneeded I will not insist on it. I was just thinking loud... I don't have any data neither so let's go ahead with serial DMA. Best regards, Krzysztof