From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752612AbcEYKL6 (ORCPT ); Wed, 25 May 2016 06:11:58 -0400 Received: from smtprelay.synopsys.com ([198.182.60.111]:58432 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751714AbcEYKL4 (ORCPT ); Wed, 25 May 2016 06:11:56 -0400 Subject: Re: [PATCH 3/4 v7] ASoC: dwc: Add PIO PCM extension To: Mark Brown , Jose Abreu References: <20160524164151.GM8206@sirena.org.uk> <57448A42.9050606@synopsys.com> <20160524175144.GO8206@sirena.org.uk> CC: , Carlos Palminha , Liam Girdwood , Jaroslav Kysela , Takashi Iwai , "Rob Herring" , Alexey Brodkin , , , From: Jose Abreu Message-ID: <57457A63.5060702@synopsys.com> Date: Wed, 25 May 2016 11:11:47 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <20160524175144.GO8206@sirena.org.uk> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.107.19.39] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Mark, On 24-05-2016 18:51, Mark Brown wrote: > On Tue, May 24, 2016 at 06:07:14PM +0100, Jose Abreu wrote: >> On 24-05-2016 17:41, Mark Brown wrote: > Please fix your mail client to word wrap within paragraphs at something > substantially less than 80 columns. Doing this makes your messages much > easier to read and reply to. > >>>> if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) >>>> i2s_write_reg(dev->i2s_base, ITER, 1); >>> That seems wrong, or at least something that should be separate? >>> Previously we needed interrupts for DMA operation but now we enable >>> interrupts only if we don't use DMA. It feels like we want to make the >>> change for DMA separately if only to make it clear for bisection, are we >>> 100% sure that masking the interrupt won't also mask the DMA request >>> signals? >> Indeed I thought about this and the interrupts must also be enabled when in DMA >> mode. Although there is no interrupt handler in the original driver (without >> this patches) in some setups the interrupt line may be connected to the DMA >> controller. I will drop this change and always enable interrupts. Please note >> that I don't have a setup with DMA support so I can only test using the PIO mode. > Presumably you can talk to your hardware colleagues and get them to make > you a FPGA with a DMA IP available? Its already in the todo list. > >>> This also seems wrong. We're forcing PIO if an interrupt is provided >>> rather than based on DMA being configured which means that if the >>> interrupt is wired up and happens to be described in DT we'll get worse >> How should I then determine which mode to use? >> - Check if DMA parameters are declared in DT, or >> - Check if snd_dmaengine_pcm_register() fails, or >> - Assume PIO mode will be used when compiling with PIO PCM, or >> - Something else ? > You could either unconditionally register the PIO driver and only > actually start using it if the driver is instantiated or you could check > to see if the registration function works (handling deferred probe - if > the DMA driver just didn't load yet you should wait for it). I think I will take the second option. Something like this: " ret = snd_dmaengine_pcm_register(...) if (ret == -EPROBE_DEFER) return ret; else pio_register(...); "? Best regards, Jose Miguel Abreu