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Old 12-11-2009, 11:15 AM
Alberto Milone
 
Default drm/i915: Fix sync to vblank when VGA output is turned off

On Wednesday 09 Dec 2009 14:52:41 you wrote:
> Alberto Milone wrote:
> > Hi all,
> >
> > SRU Justification:
> >
> > The problem described in this email was reported in a private OEM bug
> > report for Dell and has been solved by upstream. It's a regression in the
> > drm code which causes a massive system slowdown if we turn off the VGA
> > output.
> >
> > The patch is sane and minimal and is available in the drm-intel branch
> > and in the linux-next branch (see the link to the commit in the bug
> > report).
> >
> > I have applied (and slightly adapted, as it didn't apply cleanly to our
> > lucid and karmic git branches) and tested the patch successfully in
> > Karmic.
> >
> > The integration of this patch is very important for our Dell projects and
> > for the Ubuntu desktop at large.
> >
> > Please include the attached patch in both Karmic and Lucid ASAP.
> >
> > Bug #494461
> >
> > Thanks in advance for your time.
> >
> > Regards,
>
> This should actually have gone to stable as well as it fixes a regression.
> Also the description sounds like the integration path should be stable as
> well (as long as that is open).
> The patch itself looks like it changes semantics of an exported function.
> Before additional calls to drm_vblank_get() would return ok and increment
> the ref count. After the change, additional calls will return an error and
> not increment the count. On the good side it seems that function is only
> used within drm_irq.c and the usage seems to be ok to handle that change.
> Currently not 100% convinced to ack, but might get convinced.
>
> -Stefan
>
> -Stefan
>

Hi Stefan,

I discussed this with Jesse (who reviewed the patch). It's ok to return an
error in drm_vblank_get().

Think of the case in which a client (a direct rendered 3d app such as compiz
or a game) tries to wait on a pipe that is off (e.g. due to dpms), the client
would do so, but if the pipe went off after a client waited, the client might
never wake up. Furthermore if a pipe went off we might not catch it for a
while. For this reason it's ok to return the error to the client.

Furthermore the patch seems to be in the stable branch too:
http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6-
stable.git;a=commit;h=778c902640530371a169ad1c0356 6e7c51b09874

I hope both facts (especially the latter) can fully convince you, and if they
don't, I'll try harder

Regards,

--
Alberto Milone
Sustaining Engineer (system)
Foundations Team
Canonical OEM Services

--
kernel-team mailing list
kernel-team@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/kernel-team
 
Old 12-16-2009, 03:00 PM
Alberto Milone
 
Default drm/i915: Fix sync to vblank when VGA output is turned off

On Wednesday 16 Dec 2009 16:40:13 you wrote:
> Alberto Milone wrote:
> > Hi all,
> >
> > SRU Justification:
> >
> > The problem described in this email was reported in a private OEM bug
> > report for Dell and has been solved by upstream. It's a regression in the
> > drm code which causes a massive system slowdown if we turn off the VGA
> > output.
> >
> > The patch is sane and minimal and is available in the drm-intel branch
> > and in the linux-next branch (see the link to the commit in the bug
> > report).
> >
> > I have applied (and slightly adapted, as it didn't apply cleanly to our
> > lucid and karmic git branches) and tested the patch successfully in
> > Karmic.
> >
> > The integration of this patch is very important for our Dell projects and
> > for the Ubuntu desktop at large.
> >
> > Please include the attached patch in both Karmic and Lucid ASAP.
> >
> > Bug #494461
> >
> > Thanks in advance for your time.
> >
> > Regards,
>
> Ok, I just submitted a request to put that into stable and would apply
> it prematurely to our Karmic tree. Just one thing: Alberto, can you
> please create a public bug report with the necessary non private
> information in it to understand why this is needed? Thanks
>
> -Stefan
>

Hi Stefan,

First of all, thanks for your work.

Bug #439778 is private while bug #494461 is public. If the latter lacks the
information you need, I'm available to add further details there.

Let me know.

Regards,

--
Alberto Milone
Sustaining Engineer (system)
Foundations Team
Canonical OEM Services

--
kernel-team mailing list
kernel-team@lists.ubuntu.com
https://lists.ubuntu.com/mailman/listinfo/kernel-team
 

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