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=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH,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 8BF83C04AAF for ; Thu, 9 May 2019 04:26:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 45B582175B for ; Thu, 9 May 2019 04:26:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557376005; bh=BTFLcMlAore+8BPqJnH+mQxkkDWN3gE2tXUgHZgQ4vM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=D2KZaCxFBo8gFEh0117RomBqNh/pxBFjxssGsle0ApMW9pRns2NgznwWikwTcUDBp VlJIOIPC/jPihwJZ5RPPedM+ilpO1lIfYPRzXcpLLaLqs1p3zX+zUuadBJLS5EX+gJ +IAo3VJNJuynHdyKLUBP7mJQKxT1O7zdtn8e+J/g= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726548AbfEIE0n (ORCPT ); Thu, 9 May 2019 00:26:43 -0400 Received: from mail.kernel.org ([198.145.29.99]:55352 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725869AbfEIE0n (ORCPT ); Thu, 9 May 2019 00:26:43 -0400 Received: from localhost (unknown [106.200.210.185]) (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 CBC34216C4; Thu, 9 May 2019 04:26:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1557376001; bh=BTFLcMlAore+8BPqJnH+mQxkkDWN3gE2tXUgHZgQ4vM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YNz/u8qqH3SBUlmOJtHHegFvP57qUsdB4GleSRyfOjH1Nm8YuxaRXU8yFHPpYbJ4U p7KovupqvTuIB5w5DN6Il6iHBsbb6fcYTONbC/JhSPD1GlBGp/17XZJ4fxD3yQ7SmO uUzJPV4fD/Hp6zKxok8X3OoABBdk9pZTWSXIKm9E= Date: Thu, 9 May 2019 09:56:36 +0530 From: Vinod Koul To: Pierre-Louis Bossart Cc: Greg KH , alsa-devel@alsa-project.org, tiwai@suse.de, linux-kernel@vger.kernel.org, liam.r.girdwood@linux.intel.com, broonie@kernel.org, srinivas.kandagatla@linaro.org, jank@cadence.com, joe@perches.com, Sanyog Kale Subject: Re: [alsa-devel] [RFC PATCH 1/7] soundwire: Add sysfs support for master(s) Message-ID: <20190509042636.GY16052@vkoul-mobl> References: <20190507052732.GD16052@vkoul-mobl> <20190507055432.GB17986@kroah.com> <20190507110331.GL16052@vkoul-mobl> <20190507111956.GB1092@kroah.com> <10fef156-7b01-7a08-77b4-ae3153eaaabc@linux.intel.com> <20190508074606.GV16052@vkoul-mobl> <20190508091628.GB1858@kroah.com> <20190508165945.GC6157@kroah.com> <0b8d5238-6894-e2b4-5522-28636e40dd63@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0b8d5238-6894-e2b4-5522-28636e40dd63@linux.intel.com> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08-05-19, 15:57, Pierre-Louis Bossart wrote: > > > On 5/8/19 11:59 AM, Greg KH wrote: > > On Wed, May 08, 2019 at 11:42:15AM -0500, Pierre-Louis Bossart wrote: > > > > > > > > > On 5/8/19 4:16 AM, Greg KH wrote: > > > > On Wed, May 08, 2019 at 01:16:06PM +0530, Vinod Koul wrote: > > > > > On 07-05-19, 17:49, Pierre-Louis Bossart wrote: > > > > > > > > > > > > > > The model here is that Master device is PCI or Platform device and then > > > > > > > > creates a bus instance which has soundwire slave devices. > > > > > > > > > > > > > > > > So for any attribute on Master device (which has properties as well and > > > > > > > > representation in sysfs), device specfic struct (PCI/platfrom doesn't > > > > > > > > help). For slave that is not a problem as sdw_slave structure takes care > > > > > > > > if that. > > > > > > > > > > > > > > > > So, the solution was to create the psedo sdw_master device for the > > > > > > > > representation and have device-specific structure. > > > > > > > > > > > > > > Ok, much like the "USB host controller" type device. That's fine, make > > > > > > > such a device, add it to your bus, and set the type correctly. And keep > > > > > > > a pointer to that structure in your device-specific structure if you > > > > > > > really need to get to anything in it. > > > > > > > > > > > > humm, you lost me on the last sentence. Did you mean using > > > > > > set_drv/platform_data during the init and retrieving the bus information > > > > > > with get_drv/platform_data as needed later? Or something else I badly need > > > > > > to learn? > > > > > > > > > > IIUC Greg meant we should represent a soundwire master device type and > > > > > use that here. Just like we have soundwire slave device type. Something > > > > > like: > > > > > > > > > > struct sdw_master { > > > > > struct device dev; > > > > > struct sdw_master_prop *prop; > > > > > ... > > > > > }; > > > > > > > > > > In show function you get master from dev (container of) and then use > > > > > that to access the master properties. So int.sdw.0 can be of this type. > > > > > > > > Yes, you need to represent the master device type if you are going to be > > > > having an internal representation of it. > > > > > > Humm, confused...In the existing code bus and master are synonyms, see e.g. > > > following code excerpts: > > > > > > * sdw_add_bus_master() - add a bus Master instance > > > * @bus: bus instance > > > * > > > * Initializes the bus instance, read properties and create child > > > * devices. > > > > > > struct sdw_bus { > > > struct device *dev; <<< pointer here > > > > That's the pointer to what? The device that the bus is "attached to" > > (i.e. parent, like a platform device or a pci device)? > > > > Why isn't this a "real" device in itself? Correct, I am revisiting this and I think I have a fair idea of expectations here (looking at usb and greybus model), will hack something up > Allow me to provide a bit of background. I am not trying to be pedantic but > make sure we are on the same page. > > The SoundWire spec only defines a Master and Slaves attached to that Master. > > In real applications, there is a need to have multiple links, which can > possibly operate in synchronized ways, so Intel came up with the concept of > Controller, which expose multiple Master interfaces that are in sync (two > streams can start at exactly the same clock edge of different links). > > The Controller is exposed in ACPI as a child of the HDAudio controller (ACPI > companion of a PCI device). The controller exposes a 'master-count' and a > set of link-specific properties needed for bandwidth/clock scaling. > > For some reason, our Windows friends did not want to have a device for each > Master interface, likely because they did not want to load a driver per > Master interface or have 'yellow bangs'. > > So the net result is that we have the following hierarchy in ACPI > > Device(HDAS) // HDaudio controller > Device(SNDW) // SoundWire Controller > Device(SDW0) { // Slave0 > _ADR(link0, vendorX, partY...) > } > Device(SDW1) { // Slave0 > _ADR(link0, vendorX, partY...) > } > Device(SDW2) { // Slave0 > _ADR(link1, vendorX, partY...) > } > Device(SDWM) { // Slave0 > _ADR(linkM, vendorX, partY...) > } > > There is no master device represented in ACPI and the only way by which we > know to which Master a Slave device is attached by looking up the _ADR which > contains the link information. > > So, coming back to the plot, when we parse the Controller properties, we > find out how many Master interfaces we have, create a platform_device for > each of them, then initialize all the bus stuff. So the idea here would be to go back and create a sdw_master device and use that in the bus instance. I think it should be doable.. > > I thought I asked that a long time ago when first reviewing these > > patches... Sorry my fault, I should have fixed it back then. > > > > > unsigned int link_id; > > > struct list_head slaves; > > > DECLARE_BITMAP(assigned, SDW_MAX_DEVICES); > > > struct mutex bus_lock; > > > struct mutex msg_lock; > > > const struct sdw_master_ops *ops; > > > const struct sdw_master_port_ops *port_ops; > > > struct sdw_bus_params params; > > > struct sdw_master_prop prop; > > > > > > The existing code creates a platform_device in > > > drivers/soundwire/intel_init.c, and it's assigned by the following code: > > > > The core creates a platform device, don't assume you can "take it over" > > :) > > > > That platform device lives on the platform bus, you need a "master" > > device that lives on your soundbus bus. > > > > Again, look at how USB does this. Or better yet, greybus, as that code > > is a lot smaller and simpler. > > The learning curve is not small here... > > > > > > > static int intel_probe(struct platform_device *pdev) > > > { > > > struct sdw_cdns_stream_config config; > > > struct sdw_intel *sdw; > > > int ret; > > > > > > sdw = devm_kzalloc(&pdev->dev, sizeof(*sdw), GFP_KERNEL); > > > [snip] > > > sdw->cdns.dev = &pdev->dev; > > > sdw->cdns.bus.dev = &pdev->dev; > > > > Gotta love the lack of reference counting :( > > > > > I really don't see what you are hinting at, sorry, unless we are talking > > > about major surgery in the code. Not really we have object here which should contain a real device for master and need plumbing for it.. > > It sounds like you need a device on your bus that represents the master, > > as you have attributes associated with it, and other things. You can't > > put attributes on a random pci or platform device, as you do not "own" > > that device. > > > > does that help? > > Looks like we are doing things wrong at multiple levels. > > It might be better to have a more 'self-contained' solution where the bus > initialization creates/registers a master device instead of having this > proxy platform_device. That would avoid all these refcount issues and make > the translation from device to bus straightforward. yes that is my thinking as well. We still need to link to platform/pci/whatever device you have and grab a refcount to that one. > Am I on the right track or still in the weeds? -- ~Vinod