From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754001AbaHUIeb (ORCPT ); Thu, 21 Aug 2014 04:34:31 -0400 Received: from www.linutronix.de ([62.245.132.108]:56474 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753468AbaHUIe2 (ORCPT ); Thu, 21 Aug 2014 04:34:28 -0400 Message-ID: <53F5AF0D.5060409@linutronix.de> Date: Thu, 21 Aug 2014 10:34:21 +0200 From: Sebastian Andrzej Siewior User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.0 MIME-Version: 1.0 To: Tony Lindgren CC: linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org, balbi@ti.com, Vinod Koul , Greg Kroah-Hartman Subject: Re: [PATCH 15/15] tty: serial: 8250: omap: add dma support References: <1408124563-31541-1-git-send-email-bigeasy@linutronix.de> <1408124563-31541-16-git-send-email-bigeasy@linutronix.de> <20140815210211.GD9239@atomide.com> In-Reply-To: <20140815210211.GD9239@atomide.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/15/2014 11:02 PM, Tony Lindgren wrote: > * Sebastian Andrzej Siewior [140815 11:13]: >> +#ifdef CONFIG_SERIAL_8250_DMA >> + if (pdev->dev.of_node) { >> + /* >> + * Oh DMA support. If there are no DMA properties in the DT then >> + * we will fall back to a generic DMA channel which does not >> + * really work here. To ensure that we do not get a generic DMA >> + * channel assigned, we have the the_no_dma_filter_fn() here. >> + * To avoid "failed to request DMA" messages we check for DMA >> + * properties in DT. >> + */ >> + ret = of_property_count_strings(pdev->dev.of_node, "dma-names"); >> + if (ret == 2) { >> + up.dma = &priv->omap8250_dma; >> + priv->omap8250_dma.fn = the_no_dma_filter_fn; >> + priv->omap8250_dma.rx_size = RX_TRIGGER; >> + priv->omap8250_dma.rxconf.src_maxburst = RX_TRIGGER; >> + priv->omap8250_dma.txconf.dst_maxburst = TX_TRIGGER; >> + >> + if (of_machine_is_compatible("ti,am33xx")) >> + up.bugs |= UART_BUG_DMATX; >> + } >> + } >> +#endif > > Hmm I wonder if there's a more generic solution to this? To what exactly? The trigger level, the TX-bug or using DMA in the first place? > It would be also nice to be able to specify the use of DMA from > the board specific .dts file. Really? I don't see this requirement for MMC for instance. However you still could provide an empty "dma-names" property in your board .dts file if you do not want use DMA. Would this work? > Also, with DMA enabled, looks like omap deeper idle states are > blocked as the DMA stays reserved. After I commented out the > DMA info for my console UART, PM started working. Hmm. This would explain something. This would mean that I should cancel the RX DMA transfer in the PM-suspend routine. Let me see how that works. > Regards, > > Tony Sebastian