[3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Jonathan Nieder]

Hi Ben,

Please consider

  cc22a938fc1d drm/i915: add Ivy Bridge GT2 Server entries, 2012-03-29

for application to the 3.2.y tree.  It adds a PCI id to the i915
driver, making kms work.  It was applied during the 3.4-rc2 cycle, so
newer stable kernels don't need it.

Maik Zumstrull tried it[1] on top of 3.2.30 and found it to work ok
(thanks!).

Note that pre-2.4.34 versions of libdrm don't cope well with that
card, with or without this patch:

 - without this patch, modern X errors out instead of starting,
   because the intel driver requires kms.  (In a hypothetical better
   world, userspace would know to fall back to vesa or something.)

 - with this patch and with libdrm patch 2.4.34~22 (intel: add Ivy
   Bridge GT2 server variant, 2012-03-29), X should work great

 - with this patch, without libdrm 2.4.34~22, but with libdrm patch
   2.4.38~10 (intel: Bail gracefully if we encounter an unknown Intel
   device, 2012-07-25) applied, X should error out instead of starting

 - with this patch, and with libdrm lacking 2.4.34~22 and 2.4.38~10,
   X freezes at startup.

"No regressions" means you probably shouldn't take this patch without
a safety to work around the old X userspace, unless you can shout
enough in release notes to get people to apply 2.4.38~10 to libdrm and
maintain sanity. ;)

Hmm?
Jonathan

[1] http://bugs.debian.org/684767

Re: [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Ben Hutchings]

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On Mon, 2012-10-01 at 03:24 -0700, Jonathan Nieder wrote:
> Hi Ben,
> 
> Please consider
> 
>   cc22a938fc1d drm/i915: add Ivy Bridge GT2 Server entries, 2012-03-29
> 
> for application to the 3.2.y tree.  It adds a PCI id to the i915
> driver, making kms work.  It was applied during the 3.4-rc2 cycle, so
> newer stable kernels don't need it.
> 
> Maik Zumstrull tried it[1] on top of 3.2.30 and found it to work ok
> (thanks!).
> 
> Note that pre-2.4.34 versions of libdrm don't cope well with that
> card, with or without this patch:
[...]
>  - with this patch, and with libdrm lacking 2.4.34~22 and 2.4.38~10,
>    X freezes at startup.
> 
> "No regressions" means you probably shouldn't take this patch without
> a safety to work around the old X userspace,
[...]

Then this workaround is also required in mainline.  And once that's
done, I can take both patches.

Ben.

-- 
Ben Hutchings
You can't have everything.  Where would you put it?

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Re: [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Chris Wilson]

On Sun, 07 Oct 2012 15:01:17 +0100, Ben Hutchings <ben@decadent.org.uk> wrote:
> On Mon, 2012-10-01 at 03:24 -0700, Jonathan Nieder wrote:
> > Hi Ben,
> > 
> > Please consider
> > 
> >   cc22a938fc1d drm/i915: add Ivy Bridge GT2 Server entries, 2012-03-29
> > 
> > for application to the 3.2.y tree.  It adds a PCI id to the i915
> > driver, making kms work.  It was applied during the 3.4-rc2 cycle, so
> > newer stable kernels don't need it.
> > 
> > Maik Zumstrull tried it[1] on top of 3.2.30 and found it to work ok
> > (thanks!).
> > 
> > Note that pre-2.4.34 versions of libdrm don't cope well with that
> > card, with or without this patch:
> [...]
> >  - with this patch, and with libdrm lacking 2.4.34~22 and 2.4.38~10,
> >    X freezes at startup.
> > 
> > "No regressions" means you probably shouldn't take this patch without
> > a safety to work around the old X userspace,
> [...]
> 
> Then this workaround is also required in mainline.  And once that's
> done, I can take both patches.

The bugs Jonathan mentions are both in userspace packages; not
recognising the existence of Bromlow, and then misprogramming it. There
are no other kernel patches required specifically for this chipset,
afaik.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre

Re: [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Ben Hutchings]

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On Sun, 2012-10-07 at 15:11 +0100, Chris Wilson wrote:
> On Sun, 07 Oct 2012 15:01:17 +0100, Ben Hutchings <ben@decadent.org.uk> wrote:
> > On Mon, 2012-10-01 at 03:24 -0700, Jonathan Nieder wrote:
> > > Hi Ben,
> > > 
> > > Please consider
> > > 
> > >   cc22a938fc1d drm/i915: add Ivy Bridge GT2 Server entries, 2012-03-29
> > > 
> > > for application to the 3.2.y tree.  It adds a PCI id to the i915
> > > driver, making kms work.  It was applied during the 3.4-rc2 cycle, so
> > > newer stable kernels don't need it.
> > > 
> > > Maik Zumstrull tried it[1] on top of 3.2.30 and found it to work ok
> > > (thanks!).
> > > 
> > > Note that pre-2.4.34 versions of libdrm don't cope well with that
> > > card, with or without this patch:
> > [...]
> > >  - with this patch, and with libdrm lacking 2.4.34~22 and 2.4.38~10,
> > >    X freezes at startup.
> > > 
> > > "No regressions" means you probably shouldn't take this patch without
> > > a safety to work around the old X userspace,
> > [...]
> > 
> > Then this workaround is also required in mainline.  And once that's
> > done, I can take both patches.
> 
> The bugs Jonathan mentions are both in userspace packages; not
> recognising the existence of Bromlow, and then misprogramming it.

Yes, I understand that.

> There
> are no other kernel patches required specifically for this chipset,
> afaik.

If upgrading the kernel currently triggers a (more) serious bug in
typical userland then the kernel should work around that.  If I've
misunderstood, and the userland behaviour is roughly equally broken with
or without this change, then I'll be happy to take it.

Ben.

-- 
Ben Hutchings
You can't have everything.  Where would you put it?

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Re: [Intel-gfx] [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Julien Cristau]

On Mon, Oct  1, 2012 at 03:24:32 -0700, Jonathan Nieder wrote:

>  - without this patch, modern X errors out instead of starting,
>    because the intel driver requires kms.  (In a hypothetical better
>    world, userspace would know to fall back to vesa or something.)
> 
I'd expect X to start with vesa or fbdev, rather than erroring out?

Cheers,
Julien

Re: [Intel-gfx] [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Maik Zumstrull]

On Sun, Oct 7, 2012 at 7:26 PM, Julien Cristau <jcristau@debian.org> wrote:
> On Mon, Oct  1, 2012 at 03:24:32 -0700, Jonathan Nieder wrote:
>
>>  - without this patch, modern X errors out instead of starting,
>>    because the intel driver requires kms.  (In a hypothetical better
>>    world, userspace would know to fall back to vesa or something.)
>>
> I'd expect X to start with vesa or fbdev, rather than erroring out?

There's a corner case when X and the kernel know about the graphics
device, but libdrm doesn't, in which case an assertion in the X driver
fails and X doesn't start. Upstream libdrm has been okay for a few
releases. A bug against Debian libdrm has been open for a while, but
they seem to disagree about the importance, nothing has happened. In
fairness, this device seems to be rare so far. I'm not really using
mine any more, I put an extra graphics card in the box.

Re: [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Jonathan Nieder]

Maik Zumstrull wrote:
> On Sun, Oct 7, 2012 at 7:26 PM, Julien Cristau <jcristau@debian.org> wrote:
>> On Mon, Oct  1, 2012 at 03:24:32 -0700, Jonathan Nieder wrote:

>>>  - without this patch, modern X errors out instead of starting,
[...]
>> I'd expect X to start with vesa or fbdev, rather than erroring out?
>
> There's a corner case when X and the kernel know about the graphics
> device, but libdrm doesn't, in which case an assertion in the X driver
> fails and X doesn't start. Upstream libdrm has been okay for a few
> releases.

I think Julien means the case where the kernel does not know about the
graphics device.  From [1]:

| 3.2 crashes as well, but not as hard as 3.4. With 3.2, X doesn't come
| up, but you can switch to a console and reboot. 3.4 needs the reset
| button.

X should have been able to start using the vesa or fbdev driver.  I'm
not sure why that doesn't happen --- do you have an Xorg log from
booting and trying to start X with a 3.2.y kernel without the
"drm/i915: add Ivy Bridge GT2 Server entries" patch?

Thanks,
Jonathan

[1] http://bugs.debian.org/684767

Re: [3.2.y] drm/i915: add Ivy Bridge GT2 Server entries

[Maik Zumstrull]

On Sun, Oct 7, 2012 at 7:44 PM, Jonathan Nieder <jrnieder@gmail.com> wrote:

> X should have been able to start using the vesa or fbdev driver.  I'm
> not sure why that doesn't happen --- do you have an Xorg log from
> booting and trying to start X with a 3.2.y kernel without the
> "drm/i915: add Ivy Bridge GT2 Server entries" patch?

No, and it would be a bit of fiddling to get one. Like I said, I've
modified that system with a graphics card since. If it's important, I
could get it done, but probably not next week, I'll be traveling and
otherwise busy.