Nouveau - Jan 2015 - [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 at
gmail.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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On 01/06/2015 07:49 PM, Thierry Reding wrote:
> * PGP Signed by an unknown key
>
> 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 at
gmail.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.
Do we really want the platform driver always built with the PCI driver even
there is no dependency between them. Actually I have some patches to
build the platform driver with !CONFIG_PCI and would like to post them maybe
later.

Thanks,
Vince
>
> 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.

On Tue, Jan 06, 2015 at 08:27:06PM +0800, Vince Hsu
wrote:
> 
> On 01/06/2015 07:49 PM, Thierry Reding wrote:
> >* PGP Signed by an unknown key
> >
> >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
at gmail.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.
> Do we really want the platform driver always built with the PCI driver even
> there is no dependency between them. Actually I have some patches to
> build the platform driver with !CONFIG_PCI and would like to post them
maybe
> later.
I do see some advantage in making Nouveau build with !CONFIG_PCI because
it allows building the driver for an SoC without PCI. But I think always
compiling whatever is available won't hurt. Nouveau itself is rather big
(~1 MiB of text and ~120 KiB of data) whereas the platform code weighs
in at around 1.5 KiB of text and 108 B of data. I suspect that the PCI
glue is equally negligible.

Thierry
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