Re: [PATCH 01/12] drm/amdgpu: add amd_gnb_bus support

From: Felix Kuehling <felix.kuehling@amd.com>
To: Mark Brown <broonie@kernel.org>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	maruthi.bayyavarapu@amd.com, lgirdwood@gmail.com,
	Maling list - DRI developers <dri-devel@lists.freedesktop.org>,
	perex@perex.cz, Alex Deucher <alexander.deucher@amd.com>
Subject: Re: [PATCH 01/12] drm/amdgpu: add amd_gnb_bus support
Date: Fri, 7 Aug 2015 16:03:08 -0400	[thread overview]
Message-ID: <55C50EFC.4050407@amd.com> (raw)
In-Reply-To: <20150807182401.GK10301@sirena.org.uk>

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On 15-08-07 02:24 PM, Mark Brown wrote:
> Like I say this just sounds like exactly the sort of thing we handle
> with an MFD, it's a very common pattern. 

OK, the MFD documentation in Documentation/devicetree/bindings/mfd/
seemed to imply a dependency on a devicetree. It took me a moment to
realize that's just the most common scenario.

In our case we don't have a devicetree, we're talking about a PC
platform. The GPU (GNB) is a PCIe device. Does the following sound like
proper use of the MFD framework for our case?

 1. GPU driver gets initialized, detects a GPU with audio co-processor (ACP)
 2. GPU driver registers mfd_cell for the ACP device using
    mfd_add_hotplug_devices
      * It's not really hot-plug, but the mem_base, irq_base, irq_domain
        parameters don't make sense for us
 3. Platform_data in the MFD cell contains audio driver-specific data,
    function pointers, etc. for the audio driver to use
 4. Audio driver binds to platform device created by
    mfd_add_hotplug_devices based on driver name

Or do we have to convert our GPU device to be an MFD cell itself, a peer
of the ACP cell?

Thanks,
  Felix

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