Nouveau - Jan 2015 - [PATCH nouveau 09/11] drm: export some variable and functions to resue the PM functions

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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On Tue, Jan 6, 2015 at 9:37 AM, Thierry Reding <thierry.reding at
gmail.com> wrote:
> 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.
The much bigger reductions in size would be from getting rid of all
the stuff that's not used at all on a GK20A, like all the firmware,
and a whole bunch of logic. I had a series that split things up into
nv04/nv50/nvc0 categories. I believe it was considered undesirable due
to increased build complexity. (It wasn't a nice modularized
separation but rather just a compile-time setting.) Shouldn't be too
hard to regenerate though.

  -ilia

On Tue, Jan 06, 2015 at 09:44:01AM -0500, Ilia Mirkin
wrote:
> On Tue, Jan 6, 2015 at 9:37 AM, Thierry Reding <thierry.reding at
gmail.com> wrote:
> > 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.
> 
> The much bigger reductions in size would be from getting rid of all
> the stuff that's not used at all on a GK20A, like all the firmware,
> and a whole bunch of logic. I had a series that split things up into
> nv04/nv50/nvc0 categories. I believe it was considered undesirable due
> to increased build complexity. (It wasn't a nice modularized
> separation but rather just a compile-time setting.) Shouldn't be too
> hard to regenerate though.
Would you happen to remember the amount of savings for enabling only
nvc0? I'm not overly concerned with the module being 1 MiB on Tegra,
though. Most boards tend to have 2 GiB+ of memory these days and the
kernel footprint is pretty big without Nouveau anyway.

Thierry
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