From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 001F5C43219 for ; Sat, 4 May 2019 10:23:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5AEB2084A for ; Sat, 4 May 2019 10:23:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556965395; bh=l3Xmchzoy355shuJN+rybTT5lgs3HpoVHmcBPPwvdw0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=T4BXH1+v79NWcVS4XXLbeUy1cWU+UcATiiFHBVmX5ehzuhOA4tn9zuE2s305/fJKS W8ZlJXe7PNe0kQGaYqoACaiLBOuTaVfp1S810TWLhTApcDDa3iJxkzbTjK5E44+d4s 1Pe3eTum3v5F/VFbjnAeQVVkoGy+bdEHKfXzvnOU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726641AbfEDKXP (ORCPT ); Sat, 4 May 2019 06:23:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:33584 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726631AbfEDKXP (ORCPT ); Sat, 4 May 2019 06:23:15 -0400 Received: from localhost (unknown [171.76.113.243]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 34DC1206BB; Sat, 4 May 2019 10:23:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556965394; bh=l3Xmchzoy355shuJN+rybTT5lgs3HpoVHmcBPPwvdw0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=vIvgQAAJjm99iKHQb50KLr6KkU85Hi9OPPJZZXOdBz6InhdjA7o2UBQvsSdxVBy2a snTo30dEEUyOrMigvD1dKsY6aXWLjuHoxvUbV1b0hLrxvUpGGnacaLhgZ5zkuSJDVx XXQBBqJW5SIfjZVJf41xQhnvaKq+nnbnvSQHWbDU= Date: Sat, 4 May 2019 15:53:04 +0530 From: Vinod Koul To: Sameer Pujar Cc: dan.j.williams@intel.com, tiwai@suse.com, jonathanh@nvidia.com, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] [RFC] dmaengine: add fifo_size member Message-ID: <20190504102304.GZ3845@vkoul-mobl.Dlink> References: <1556623828-21577-1-git-send-email-spujar@nvidia.com> <20190502060446.GI3845@vkoul-mobl.Dlink> <20190502122506.GP3845@vkoul-mobl.Dlink> <3368d1e1-0d7f-f602-5b96-a978fcf4d91b@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <3368d1e1-0d7f-f602-5b96-a978fcf4d91b@nvidia.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On 02-05-19, 18:59, Sameer Pujar wrote: > > On 5/2/2019 5:55 PM, Vinod Koul wrote: > > On 02-05-19, 16:23, Sameer Pujar wrote: > > > On 5/2/2019 11:34 AM, Vinod Koul wrote: > > > > On 30-04-19, 17:00, Sameer Pujar wrote: > > > > > During the DMA transfers from memory to I/O, it was observed that transfers > > > > > were inconsistent and resulted in glitches for audio playback. It happened > > > > > because fifo size on DMA did not match with slave channel configuration. > > > > > > > > > > currently 'dma_slave_config' structure does not have a field for fifo size. > > > > > Hence the platform pcm driver cannot pass the fifo size as a slave_config. > > > > > Note that 'snd_dmaengine_dai_dma_data' structure has fifo_size field which > > > > > cannot be used to pass the size info. This patch introduces fifo_size field > > > > > and the same can be populated on slave side. Users can set required size > > > > > for slave peripheral (multiple channels can be independently running with > > > > > different fifo sizes) and the corresponding sizes are programmed through > > > > > dma_slave_config on DMA side. > > > > FIFO size is a hardware property not sure why you would want an > > > > interface to program that? > > > > > > > > On mismatch, I guess you need to take care of src/dst_maxburst.. > > > Yes, FIFO size is a HW property. But it is SW configurable(atleast in my > > > case) on > > > slave side and can be set to different sizes. The src/dst_maxburst is > > Are you sure, have you talked to HW folks on that? IIUC you are > > programming the data to be used in FIFO not the FIFO length! > Yes, I mentioned about FIFO length. > > 1. MAX FIFO size is fixed in HW. But there is a way to limit the usage per > channel >    in multiples of 64 bytes. > 2. Having a separate member would give independent control over MAX BURST > SIZE and >    FIFO SIZE. > > > > > programmed > > > for specific values, I think this depends on few factors related to > > > bandwidth > > > needs of client, DMA needs of the system etc., > > Precisely > > > > > In such cases how does DMA know the actual FIFO depth of slave peripheral? > > Why should DMA know? Its job is to push/pull data as configured by > > peripheral driver. The peripheral driver knows and configures DMA > > accordingly. > I am not sure if there is any HW logic that mandates DMA to know the size > of configured FIFO depth on slave side. I will speak to HW folks and > would update here. I still do not comprehend why dma would care about slave side configuration. In the absence of patch which uses this I am not sure what you are trying to do... > > > > > Request for feedback/suggestions. > > > > > > > > > > Signed-off-by: Sameer Pujar > > > > > --- > > > > > include/linux/dmaengine.h | 3 +++ > > > > > 1 file changed, 3 insertions(+) > > > > > > > > > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > > > > > index d49ec5c..9ec198b 100644 > > > > > --- a/include/linux/dmaengine.h > > > > > +++ b/include/linux/dmaengine.h > > > > > @@ -351,6 +351,8 @@ enum dma_slave_buswidth { > > > > > * @slave_id: Slave requester id. Only valid for slave channels. The dma > > > > > * slave peripheral will have unique id as dma requester which need to be > > > > > * pass as slave config. > > > > > + * @fifo_size: Fifo size value. The dma slave peripheral can configure required > > > > > + * fifo size and the same needs to be passed as slave config. > > > > > * > > > > > * This struct is passed in as configuration data to a DMA engine > > > > > * in order to set up a certain channel for DMA transport at runtime. > > > > > @@ -376,6 +378,7 @@ struct dma_slave_config { > > > > > u32 dst_port_window_size; > > > > > bool device_fc; > > > > > unsigned int slave_id; > > > > > + u32 fifo_size; > > > > > }; > > > > > /** > > > > > -- > > > > > 2.7.4 -- ~Vinod