From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752278AbeDCPdD (ORCPT ); Tue, 3 Apr 2018 11:33:03 -0400 Received: from smtp03.smtpout.orange.fr ([80.12.242.125]:38023 "EHLO smtp.smtpout.orange.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751434AbeDCPdB (ORCPT ); Tue, 3 Apr 2018 11:33:01 -0400 X-ME-Helo: belgarion X-ME-Auth: amFyem1pay5yb2JlcnRAb3JhbmdlLmZy X-ME-Date: Tue, 03 Apr 2018 17:33:00 +0200 X-ME-IP: 86.201.130.131 From: Robert Jarzmik To: Arnd Bergmann Cc: Daniel Mack , Haojian Zhuang , Vinod Koul , Jaroslav Kysela , Takashi Iwai , Liam Girdwood , Mark Brown , Linux ARM , Linux Kernel Mailing List , alsa-devel@alsa-project.org Subject: Re: [PATCH 14/15] ARM: pxa: change SSP devices allocation References: <20180402142656.26815-1-robert.jarzmik@free.fr> <20180402142656.26815-15-robert.jarzmik@free.fr> X-URL: http://belgarath.falguerolles.org/ Date: Tue, 03 Apr 2018 17:32:58 +0200 In-Reply-To: (Arnd Bergmann's message of "Tue, 3 Apr 2018 09:06:46 +0200") Message-ID: <87lge4485x.fsf@belgarion.home> User-Agent: Gnus/5.130008 (Ma Gnus v0.8) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Arnd Bergmann writes: chop chop ... removed several mail recipients to leave only the ASoC / PXA subset ... > On Mon, Apr 2, 2018 at 4:26 PM, Robert Jarzmik wrote: > >> >> +static struct pxa_ssp_info pxa_ssp_infos[] = { >> + { .dma_chan_rx_name = "ssp1_rx", .dma_chan_tx_name = "ssp1_tx", }, >> + { .dma_chan_rx_name = "ssp1_rx", .dma_chan_tx_name = "ssp1_tx", }, >> + { .dma_chan_rx_name = "ssp2_rx", .dma_chan_tx_name = "ssp2_tx", }, >> + { .dma_chan_rx_name = "ssp2_rx", .dma_chan_tx_name = "ssp2_tx", }, >> + { .dma_chan_rx_name = "ssp3_rx", .dma_chan_tx_name = "ssp3_tx", }, >> + { .dma_chan_rx_name = "ssp3_rx", .dma_chan_tx_name = "ssp3_tx", }, >> + { .dma_chan_rx_name = "ssp4_rx", .dma_chan_tx_name = "ssp4_tx", }, >> + { .dma_chan_rx_name = "ssp4_rx", .dma_chan_tx_name = "ssp4_tx", }, >> +}; > > This part looks odd to me, you're adding an extra level of indirection to > do two stages of lookups in some form of platform data. That's unfortunately right. > Why can't you just always use "rx" and "tx" as the names here? Well I couldn't. I'll explain you why, and maybe you'll find a better solution. That all is related to how ASoC and SSP interact. If I remember correctly, here is how it works : - the DMA channel is requested in sound/arm/pxa2xx-pcm-lib.c:128 return snd_dmaengine_pcm_open( substream, dma_request_slave_channel(rtd->platform->dev, The trick is that the device here is _not_ the SSP one, it's if memory serves me well the pxa-pcm-audio one. As a consequence, the device cannot be used to differenciate which SSP exactly is providing the sound samples stream. This information is nevertheless required to choose the correct requestor line, which is a 1-to-1 match to the SSP port. The indirection in the channel name is used to choose the correct requestor line for a given SSP port providing the samples. It also must be underlined that this dma request serves both AC97 and SSP as sample providers. > (also, I don't see why each line is duplicated, but I'm sure there's > an easy answer for that). Ahh that is an unfortunate rebase most probably :) Cheers. -- Robert