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

From: Mark Brown <broonie@kernel.org>
To: Alex Deucher <alexdeucher@gmail.com>
Cc: Chunming Zhou <david1.zhou@amd.com>,
	"alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	maruthi.bayyavarapu@amd.com, Takashi Iwai <tiwai@suse.de>,
	Felix Kuehling <Felix.Kuehling@amd.com>,
	lgirdwood@gmail.com,
	Maling list - DRI developers <dri-devel@lists.freedesktop.org>,
	Alex Deucher <alexander.deucher@amd.com>,
	Dave Airlie <airlied@gmail.com>
Subject: Re: [PATCH 01/12] drm/amdgpu: add amd_gnb_bus support
Date: Fri, 7 Aug 2015 18:20:28 +0100	[thread overview]
Message-ID: <20150807172028.GJ10301@sirena.org.uk> (raw)
In-Reply-To: <CADnq5_NihZCFEaL150Kt0LWCUBp6eQzne-O0JcCFE0-vHj7ZBQ@mail.gmail.com>

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On Fri, Aug 07, 2015 at 10:17:36AM -0400, Alex Deucher wrote:
> On Fri, Aug 7, 2015 at 6:25 AM, Mark Brown <broonie@kernel.org> wrote:

> > Looking at the code I'm not seeing too much bus specific except for the
> > above which looks like the sort of device we usually represent as a MFD
> > (with the MFD providing resource distribution and arbitration between
> > various component devices which fit into the subsystem).  Why code a new
> > bus for this device?

> Adding Felix who did worked on the design for this.  The idea is that
> there are hw blocks on the GPU that are controlled by drivers that are
> part of other subsystems.  Those drivers need access to resources
> (e.g., the MMIO aperture) controlled by the GPU driver.  I guess this
> is a MFD of sorts.  If this is not the preferred way to handle this
> type of device, what is?  Can you point me to another driver that
> handles this differently?

Yeah, this sounds like a MFD - see drivers/mfd and take a look at how
the drivers there deal with this.

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