From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754356AbbIIJPM (ORCPT ); Wed, 9 Sep 2015 05:15:12 -0400 Received: from mailout4.w1.samsung.com ([210.118.77.14]:47349 "EHLO mailout4.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751390AbbIIJPH (ORCPT ); Wed, 9 Sep 2015 05:15:07 -0400 X-AuditID: cbfec7f5-f794b6d000001495-ac-55eff899104f Message-id: <55EFF898.7060205@samsung.com> Date: Wed, 09 Sep 2015 11:15:04 +0200 From: Robert Baldyga User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.8.0 MIME-version: 1.0 To: Krzysztof Kozlowski , gregkh@linuxfoundation.org Cc: jslaby@suse.com, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, m.szyprowski@samsung.com Subject: Re: [PATCH 0/3] serial: samsung: Fix UART status handling and other fixes References: <1441705127-24125-1-git-send-email-r.baldyga@samsung.com> <55EF7395.2000702@samsung.com> In-reply-to: <55EF7395.2000702@samsung.com> Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFjrHLMWRmVeSWpSXmKPExsVy+t/xq7ozf7wPNTi1ltuiefF6NospGz4w Wbx+YWhxedccNoszi3vZLdYeucvuwOaxf+4ado++LasYPdZvucri8XmTXABLFJdNSmpOZllq kb5dAlfGyzk/mQpWcVWcX9rH2sA4n6OLkZNDQsBEouFxBzuELSZx4d56NhBbSGApo8Sj3wFd jFxA9jNGiblXf7CCJHgFtCQuNk1mBLFZBFQlrqxbCBZnE9CR2PJ9AlhcVCBCYvnqk4wQ9YIS PybfYwGxRQR8JW5OuAtmMwtkS3xsXgZmCwuESExZd4YdYnGaxLHzb8DinALaEiueH2DuYuQA qteTuH9RC6JVXmLzmrfMExgFZiHZMAuhahaSqgWMzKsYRVNLkwuKk9JzjfSKE3OLS/PS9ZLz czcxQkL56w7GpcesDjEKcDAq8fBOaHkfKsSaWFZcmXuIUYKDWUmEN/oTUIg3JbGyKrUoP76o NCe1+BCjNAeLkjjvzF3vQ4QE0hNLUrNTUwtSi2CyTBycUg2Mk/QPNnTtVrrtUvbXbfa6jt1d x2fp8M9mu8L9p3qafsBW7zOawjO3WfYEr7rFsXH59wl/vCapzPGrXXCruJI96nIO+9Zso5fZ HOHMNXZCDxwX1XYeuJCcfrii62XM9dn+9x7wmk6Y+Odk0Yvoi5XVqY5bfzKL3zFdUPIlc50H 2zqx/We8Z700VmIpzkg01GIuKk4EADES++phAgAA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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. Best regards, Robert