From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vignesh R Subject: Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes Date: Tue, 3 May 2016 17:30:33 +0530 Message-ID: <572892E1.90600@ti.com> References: <8737r7ght7.fsf@linutronix.de> <570339E8.6010808@hurleysoftware.com> <87y48kftip.fsf@linutronix.de> <570BE48F.60801@hurleysoftware.com> <570BED7B.9080803@linutronix.de> <570C04C1.40201@hurleysoftware.com> <570D2A46.2050106@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <570D2A46.2050106@linutronix.de> Sender: linux-kernel-owner@vger.kernel.org To: Sebastian Andrzej Siewior , Peter Hurley , John Ogness , Tony Lindgren , nsekhar@ti.com Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux-omap@vger.kernel.org List-Id: linux-omap@vger.kernel.org Hi, On 04/12/2016 10:33 PM, Sebastian Andrzej Siewior wrote: > On 04/11/2016 10:10 PM, Peter Hurley wrote: >> On 04/11/2016 11:31 AM, Sebastian Andrzej Siewior wrote: >>> On 04/11/2016 07:53 PM, Peter Hurley wrote: >>>> 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: [...] >> *am335x* > > I am not sure if the limitations are based on the DMA engine or the > >> - requires write to tx fifo to trigger tx dma (ie. OMAP_DMA_TX_KICK >> workaround necessitating completely different tx dma completion handler) > > This one for instance I don't see on BeagleBoard xM / omap36xx and > DRA7x. Both (not affected) use SDMA instead EDMA. It would be > interesting to see if DRA7x is affected once it uses EDMA. > 8250 UART DMA works fine with EDMA as the DMA engine. As per my testing, am335x + EDMA, am437x + EDMA, dra7xx + EDMA and dra72x + EDMA require OMAP_DMA_TX_KICK quirk. However when using SDMA OMAP_DMA_TX_KICK is not needed (I tested on dra7xx platform). So, it can be concluded that when using EDMA with 8250 UART tx kick is needed. -- Regards Vignesh From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932669AbcECMAy (ORCPT ); Tue, 3 May 2016 08:00:54 -0400 Received: from bear.ext.ti.com ([192.94.94.41]:42854 "EHLO bear.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755666AbcECMAw (ORCPT ); Tue, 3 May 2016 08:00:52 -0400 Subject: Re: [PATCH] tty: serial: 8250_omap: do not defer termios changes To: Sebastian Andrzej Siewior , Peter Hurley , John Ogness , Tony Lindgren , References: <8737r7ght7.fsf@linutronix.de> <570339E8.6010808@hurleysoftware.com> <87y48kftip.fsf@linutronix.de> <570BE48F.60801@hurleysoftware.com> <570BED7B.9080803@linutronix.de> <570C04C1.40201@hurleysoftware.com> <570D2A46.2050106@linutronix.de> CC: Greg Kroah-Hartman , , , From: Vignesh R Message-ID: <572892E1.90600@ti.com> Date: Tue, 3 May 2016 17:30:33 +0530 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: <570D2A46.2050106@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 Hi, On 04/12/2016 10:33 PM, Sebastian Andrzej Siewior wrote: > On 04/11/2016 10:10 PM, Peter Hurley wrote: >> On 04/11/2016 11:31 AM, Sebastian Andrzej Siewior wrote: >>> On 04/11/2016 07:53 PM, Peter Hurley wrote: >>>> 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: [...] >> *am335x* > > I am not sure if the limitations are based on the DMA engine or the > >> - requires write to tx fifo to trigger tx dma (ie. OMAP_DMA_TX_KICK >> workaround necessitating completely different tx dma completion handler) > > This one for instance I don't see on BeagleBoard xM / omap36xx and > DRA7x. Both (not affected) use SDMA instead EDMA. It would be > interesting to see if DRA7x is affected once it uses EDMA. > 8250 UART DMA works fine with EDMA as the DMA engine. As per my testing, am335x + EDMA, am437x + EDMA, dra7xx + EDMA and dra72x + EDMA require OMAP_DMA_TX_KICK quirk. However when using SDMA OMAP_DMA_TX_KICK is not needed (I tested on dra7xx platform). So, it can be concluded that when using EDMA with 8250 UART tx kick is needed. -- Regards Vignesh