From mboxrd@z Thu Jan 1 00:00:00 1970 From: Clemens Gruber Subject: Re: serial: imx: disable DMA for RS-485 on i.MX6 SMP Date: Sun, 2 Jul 2017 22:47:31 +0200 Message-ID: <20170702204731.GA7174@archie.localdomain> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Fabio Estevam Cc: linux-serial@vger.kernel.org, Greg Kroah-Hartman , Fabio Estevam , u.kleine-koenig@pengutronix.de, linux-kernel@vger.kernel.org, Fugang Duan List-Id: linux-serial@vger.kernel.org Hi Fabio, On Tue, Jun 20, 2017 at 08:49:28PM -0300, Fabio Estevam wrote: > Hi Clemens, > > On Tue, Jun 20, 2017 at 1:13 PM, Fabio Estevam wrote: > > > The subject gives the impression that the DMA will only be disabled > > for RS485, but the impact of this change is wider. > > > > For example: if I have a mx6q system with a Bluetooth serial > > connection I can no longer use DMA with your change applied. > > > > Ideally we should fix the RS485 DMA bug. If that is not possible, then > > at least we need to restrict this change to the RS485 case. > > > > Maybe we need to pass "linux,rs485-enabled-at-boot-time" in device > > tree and then use this property to deceide if DMA will be enabled or > > not: > > > > if (!uart_console(port) && !sport->dma_is_inited && !sport->rs485_enabled) > > Could you please test the two attached patches and see if it solves the issue? > > Unfortunately I no longer have access to the RS485 half-duplex board. > > Just make sure to pass 'linux,rs485-enabled-at-boot-time' in your > device tree, thanks. The two patches work for me! You can add my Tested-by tag if/when you submit them. Tested-by: Clemens Gruber Regards, Clemens