linux-kernel - Re: [Nouveau] [PATCH nouveau 09/11] drm: export some variable and functions to resue the PM functions

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Message-ID: <20150106114953.GD31830@ulmo.nvidia.com>
Date:	Tue, 6 Jan 2015 12:49:55 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Alexandre Courbot <gnurou@...il.com>
Cc:	Vince Hsu <vinceh@...dia.com>,
	Emil Velikov <emil.l.velikov@...il.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Ben Skeggs <bskeggs@...hat.com>,
	Martin Peres <martin.peres@...e.fr>,
	Roy Spliet <seven@...rod-online.com>,
	samuel.pitoiset@...il.com,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [Nouveau] [PATCH nouveau 09/11] drm: export some variable and
 functions to resue the PM functions

On Mon, Jan 05, 2015 at 08:50:18PM +0100, Alexandre Courbot wrote:
> On Mon, Jan 5, 2015 at 4:32 PM, Thierry Reding <thierry.reding@...il.com> wrote:
> > On Tue, Dec 30, 2014 at 11:18:34AM +0800, Vince Hsu wrote:
> >> Hi Emil,
> >>
> >> On 12/30/2014 10:34 AM, Emil Velikov wrote:
> >> >On 23/12/14 10:40, Vince Hsu wrote:
> >> >>This patch adds some checks in the suspend/resume functions to distinguish
> >> >>the dGPU and mobile GPU and exports some variables/functions so that the
> >> >>nouveau platform device can reuse them.
> >> >>
> >> >Hi Vince,
> >> >
> >> >Afaiu one needs to export a symbol as it's used by another module or
> >> >subsystem. With the follow up two patches you are not doing either one,
> >> >so I'd assume that you can just omit the EXPORT_* changes.
> >> The nouveau platform device driver is built as another module -
> >> nouveau_platform.ko. :)
> >
> > I'd like to hear the opinion of the nouveau people and Alex, but I'd
> > very much prefer if nouveau_platform.o was simply linked into the
> > nouveau.ko module. I don't see any good reason to keep it separate.
> 
> Yep, I agree. The decision to host platform support in a separate
> module looks misleaded if it results in additional exports that we
> would otherwise avoid. IIUC I did this to be able to use the module
> convenience macros to register the platform driver.
> 
> >
> > Something like the attached patch (untested) ought to do it.
> 
> This patch alone won't be enough for the reason I mentioned above.
> However, if Vince doesn't mind handling the platform driver
> registration manually in nouveau_drm_init/nouveau_drm_exit, I agree
> this would be the way to go.

If we do the conversion to generic power domains, the only Tegra-
specific API remaining will be the access to the fuse registers for the
speedo value. At that point we wouldn't need the ARCH_TEGRA dependency
any longer and could always build the platform driver along with the PCI
driver.

I guess we could do that even now if we simply #ifdef the various Tegra-
specific parts. That in turn would have the advantage that we don't need
to #ifdef the driver registration code. And it would help separate
things in case anybody wanted to use one of the SoC GPUs in a non-Tegra
SoC.

Thierry

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