From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754135AbcDKRx0 (ORCPT ); Mon, 11 Apr 2016 13:53:26 -0400 Received: from mail-pa0-f49.google.com ([209.85.220.49]:33297 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751216AbcDKRxX (ORCPT ); Mon, 11 Apr 2016 13:53:23 -0400 Subject: Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes To: John Ogness , Sebastian Andrzej Siewior References: <8737r7ght7.fsf@linutronix.de> <570339E8.6010808@hurleysoftware.com> <87y48kftip.fsf@linutronix.de> Cc: Greg Kroah-Hartman , Tony Lindgren , nsekhar@ti.com, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-omap@vger.kernel.org From: Peter Hurley Message-ID: <570BE48F.60801@hurleysoftware.com> Date: Mon, 11 Apr 2016 10:53:19 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <87y48kftip.fsf@linutronix.de> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/11/2016 01:18 AM, John Ogness wrote: > On 2016-04-05, Peter Hurley wrote: >> On 03/31/2016 01:41 AM, John Ogness wrote: >>> It has been observed that the TX-DMA can stall >> >> Does this happen on any other OMAP part besides am335x? >> I looked back over the LKML history of this and didn't see >> any other design implicated in this problem. > > I just ran the tests again using 4.6-rc2. I am able to reproduce the > dma-tx stall with am335x/edma and dra7/sdma. I thought we already established sdma was not to be used since the hardware does not actually support pausing without data loss. http://www.spinics.net/lists/linux-serial/msg18503.html So I'm wondering if we're carrying all this extra DMA complexity and workarounds for just am335x? > Note: To achieve the stall, both the delayed_restore and the > rx_dma_broken features of the mainline 8250_omap driver needed to > be removed. > > John Ogness >