Can recent i915 support more than 8192x8192 screen?

Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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Hello,

*TL;DR*: how can I set a 8960x2880 screen (not display) size on a T580? A
patch for i915 that I found on the internets does not seem to work.

Full story:

I'm a rather happy user of ThinkPad T580 which comes with a
high-density 3840x2160 LCD, and the following graphics hardware.

00:02.0 VGA compatible controller: Intel Corporation Device 5917 (rev 07)
(prog-if 00 [VGA controller])
        Subsystem: Lenovo Device 225a
        Flags: bus master, fast devsel, latency 0, IRQ 142
        Memory at e7000000 (64-bit, non-prefetchable) [size=16M]
        Memory at c0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at e000 [size=64]
        [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
        Capabilities: [40] Vendor Specific Information: Len=0c <?>
        Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
        Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Capabilities: [d0] Power Management version 2
        Capabilities: [100] Process Address Space ID (PASID)
        Capabilities: [200] Address Translation Service (ATS)
        Capabilities: [300] Page Request Interface (PRI)
        Kernel driver in use: i915
        Kernel modules: i915

Unfortunately attaching it to an external normal-density 2560x1440 display
means I need to apply scaling. Combined with the side-by-side arrangement
of monitors, this means I'd need to set screen size to 8960x2880. However
this does not work:

 $ xrandr --fb 8960x2880
 xrandr: screen cannot be larger than 8192x8192 (desired size 8960x2880)


I found this thread on reddit
<https://www.reddit.com/r/linux/comments/6bghzm/increasing_maximum_xorg_virtual_screen_resolution/>
about the same problem, where a user posted a simple patch claimed to be
supplied by someone on #intel-gfx. Unfortunately it does not work (or at
least is not sufficient) - after applying it xrandr does claim
that 16384x16384 is possible, but actually trying to use more
than 8192x8192 fails with an error (unfortunately I lost the exact message).

My current workaround is to pretend that the displays are arranged
vertically, but even after a few months I'm sometimes having trouble
remembering that I need to move mouse cursor UP when I want to go to LEFT
display :-)

I wonder if someone could help me here. Even just getting a definite answer
on whether my hardware can in theory support this or not would be helpful,
since I found conflicting information.

FWIW I'm on Debian stable, Linux 4.9.8x.

regards,
Marcin

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Re: Can recent i915 support more than 8192x8192 screen?

[Rodrigo Vivi]

On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
>    Hello,
>    TL;DR: how can I set a 8960x2880 screen (not display) size on a T580? A
>    patch for i915 that I found on the internets does not seem to work.
>    Full story:
>    I'm a rather happy user of ThinkPad T580 which comes with a
>    high-density 3840x2160 LCD, and the following graphics hardware.
>    00:02.0 VGA compatible controller: Intel Corporation Device 5917 (rev
>    07) (prog-if 00 [VGA controller])
>            Subsystem: Lenovo Device 225a
>            Flags: bus master, fast devsel, latency 0, IRQ 142
>            Memory at e7000000 (64-bit, non-prefetchable) [size=16M]
>            Memory at c0000000 (64-bit, prefetchable) [size=256M]
>            I/O ports at e000 [size=64]
>            [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
>            Capabilities: [40] Vendor Specific Information: Len=0c <?>
>            Capabilities: [70] Express Root Complex Integrated Endpoint,
>    MSI 00
>            Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
>            Capabilities: [d0] Power Management version 2
>            Capabilities: [100] Process Address Space ID (PASID)
>            Capabilities: [200] Address Translation Service (ATS)
>            Capabilities: [300] Page Request Interface (PRI)
>            Kernel driver in use: i915
>            Kernel modules: i915
>    Unfortunately attaching it to an external normal-density 2560x1440
>    display means I need to apply scaling. Combined with the side-by-side
>    arrangement of monitors, this means I'd need to set screen size
>    to 8960x2880. However this does not work:
>     $ xrandr --fb 8960x2880
>     xrandr: screen cannot be larger than 8192x8192 (desired size
>    8960x2880)
>    I found this [1]thread on reddit about the same problem, where a user
>    posted a simple patch claimed to be supplied by someone on #intel-gfx.
>    Unfortunately it does not work (or at least is not sufficient) - after
>    applying it xrandr does claim that 16384x16384 is possible, but
>    actually trying to use more than 8192x8192 fails with an error
>    (unfortunately I lost the exact message).

I'm afraid that it is a hardware limitation that you won't be able to
workaround. But a log would be interesting anyway... (both dmesg and xorg.0.log)

>    My current workaround is to pretend that the displays are arranged
>    vertically, but even after a few months I'm sometimes having trouble
>    remembering that I need to move mouse cursor UP when I want to go to
>    LEFT display :-)

This is another bug.... And probably the right (only?) fixable fr your
setup.

>    I wonder if someone could help me here. Even just getting a definite
>    answer on whether my hardware can in theory support this or not would
>    be helpful, since I found conflicting information.

Well, I'm afraid the right information is already there on the first
xrandr output. The rest was just misleading you.

>    FWIW I'm on Debian stable, Linux 4.9.8x.
>    regards,
>    Marcin
> 
> References
> 
>    1. https://www.reddit.com/r/linux/comments/6bghzm/increasing_maximum_xorg_virtual_screen_resolution/

> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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Re: Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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2018-07-20 22:22 GMT+02:00 Rodrigo Vivi <rodrigo.vivi@intel.com>:

> On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
> >     $ xrandr --fb 8960x2880
> >     xrandr: screen cannot be larger than 8192x8192 (desired size
> >    8960x2880)
>
> I'm afraid that it is a hardware limitation that you won't be able to
> workaround.


Interestingly, just yesterday Ville Syrjälä posted a patch series for "GTT
remapping for display",
which concludes in this hopeful-looking patch called "Bump gen4+ fb size
limits to 32kx32k:
https://lists.freedesktop.org/archives/intel-gfx/2018-July/171922.html

Which looks oddly similar to what I encountered on reddit.

I don't pretend to even understand what "GTT remapping" is, but maybe there
is hope after all? ;-)


> But a log would be interesting anyway... (both dmesg and xorg.0.log)
>

I'll try digging up that patched kernel sometime and get the messages.


>
> >    My current workaround is to pretend that the displays are arranged
> >    vertically, but even after a few months I'm sometimes having trouble
> >    remembering that I need to move mouse cursor UP when I want to go to
> >    LEFT display :-)
>
> This is another bug.... And probably the right (only?) fixable fr your
> setup.
>

Why is this a bug? What I meant is that two wide monitors fit
within 8192x8192
when using xrandr's --above but not --left-of, so I'm just using the former
despite
having a different physical arrangement.

Marcin

PS: Sorry for the initial double-post, I thought my first email was
blackholed
while I was not yet subscribed to the list.

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Re: Can recent i915 support more than 8192x8192 screen?

[Rodrigo Vivi]

On Fri, Jul 20, 2018 at 11:01:38PM +0200, Marcin Owsiany wrote:
>    2018-07-20 22:22 GMT+02:00 Rodrigo Vivi <[1]rodrigo.vivi@intel.com>:
> 
>    On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
>    >     $ xrandr --fb 8960x2880
>    >     xrandr: screen cannot be larger than 8192x8192 (desired size
>    >    8960x2880)
> 
>      I'm afraid that it is a hardware limitation that you won't be able
>      to
>      workaround.
> 
>    Interestingly, just yesterday Ville Syrjälä posted a patch series for
>    "GTT remapping for display",
>    which concludes in this hopeful-looking patch called "Bump gen4+ fb
>    size limits to 32kx32k:
>    [2]https://lists.freedesktop.org/archives/intel-gfx/2018-July/171922.ht
>    ml
>    Which looks oddly similar to what I encountered on reddit.
>    I don't pretend to even understand what "GTT remapping" is, but maybe
>    there is hope after all? ;-)

cool...  I have that series on my todo list here to take a look but I
haven't yet. I'm glad to hear that there's hope.

> 
>      But a log would be interesting anyway... (both dmesg and xorg.0.log)
> 
>    I'll try digging up that patched kernel sometime and get the messages.
> 
>      >    My current workaround is to pretend that the displays are
>      arranged
>      >    vertically, but even after a few months I'm sometimes having
>      trouble
>      >    remembering that I need to move mouse cursor UP when I want to
>      go to
>      >    LEFT display :-)
>      This is another bug.... And probably the right (only?) fixable fr
>      your
>      setup.
> 
>    Why is this a bug? What I meant is that two wide monitors fit
>    within 8192x8192
>    when using xrandr's --above but not --left-of, so I'm just using the
>    former despite
>    having a different physical arrangement.
>    Marcin
>    PS: Sorry for the initial double-post, I thought my first email was
>    blackholed

np... I approved it as soon as I saw it there.
list is open, but I have to filter the non-subscribed emails because of
so many spams...

>    while I was not yet subscribed to the list.
> 
> References
> 
>    1. mailto:rodrigo.vivi@intel.com
>    2. https://lists.freedesktop.org/archives/intel-gfx/2018-July/171922.html

> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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Re: Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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pt., 20 lip 2018, 23:35 użytkownik Rodrigo Vivi <rodrigo.vivi@intel.com>
napisał:

> On Fri, Jul 20, 2018 at 11:01:38PM +0200, Marcin Owsiany wrote:
> >    2018-07-20 22:22 GMT+02:00 Rodrigo Vivi <[1]rodrigo.vivi@intel.com>:
> >
> >    On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
>
> >    PS: Sorry for the initial double-post, I thought my first email was
> >    blackholed
>
> np... I approved it as soon as I saw it there.
> list is open, but I have to filter the non-subscribed emails because of
> so many spams...
>

I see, perhaps it might make sense to mention that the list is moderated to
https://01.org/community/participation-guidelines#list

Currently the policy makes it sound like messages from non-subscribers are
doomed for good.

Marcin

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Re: Can recent i915 support more than 8192x8192 screen?

[Rodrigo Vivi]

On Sat, Jul 21, 2018 at 09:43:53AM +0200, Marcin Owsiany wrote:
>    pt., 20 lip 2018, 23:35 użytkownik Rodrigo Vivi
>    <[1]rodrigo.vivi@intel.com> napisał:
> 
>      On Fri, Jul 20, 2018 at 11:01:38PM +0200, Marcin Owsiany wrote:
>      >    2018-07-20 22:22 GMT+02:00 Rodrigo Vivi
>      <[1][2]rodrigo.vivi@intel.com>:
>      >
>      >    On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
>      >    PS: Sorry for the initial double-post, I thought my first email
>      was
>      >    blackholed
>      np... I approved it as soon as I saw it there.
>      list is open, but I have to filter the non-subscribed emails because
>      of
>      so many spams...
> 
>    I see, perhaps it might make sense to mention that the list is
>    moderated to
>    [3]https://01.org/community/participation-guidelines#list
>    Currently the policy makes it sound like messages from non-subscribers
>    are doomed for good.

Well, we have this link on list's main page:

https://lists.freedesktop.org/mailman/listinfo/intel-gfx

So I'm not sure where you are suggesting us to add this link.

>    Marcin
> 
> References
> 
>    1. mailto:rodrigo.vivi@intel.com
>    2. mailto:rodrigo.vivi@intel.com
>    3. https://01.org/community/participation-guidelines#list

> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

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Re: Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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2018-07-24 20:37 GMT+02:00 Rodrigo Vivi <rodrigo.vivi@intel.com>:

> On Sat, Jul 21, 2018 at 09:43:53AM +0200, Marcin Owsiany wrote:
> >    pt., 20 lip 2018, 23:35 użytkownik Rodrigo Vivi
> >    <[1]rodrigo.vivi@intel.com> napisał:
> >
> >      On Fri, Jul 20, 2018 at 11:01:38PM +0200, Marcin Owsiany wrote:
> >      >    2018-07-20 22:22 GMT+02:00 Rodrigo Vivi
> >      <[1][2]rodrigo.vivi@intel.com>:
> >      >
> >      >    On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
> >      >    PS: Sorry for the initial double-post, I thought my first email
> >      was
> >      >    blackholed
> >      np... I approved it as soon as I saw it there.
> >      list is open, but I have to filter the non-subscribed emails because
> >      of
> >      so many spams...
> >
> >    I see, perhaps it might make sense to mention that the list is
> >    moderated to
> >    [3]https://01.org/community/participation-guidelines#list
> >    Currently the policy makes it sound like messages from non-subscribers
> >    are doomed for good.
>
> Well, we have this link on list's main page:
>
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
> So I'm not sure where you are suggesting us to add this link.
>

I'm not suggesting to add this link (I know it's there, that's how I found
it in the first place).
I'm suggesting to change the contents of
https://01.org/community/participation-guidelines#list to say "your posts
will need to wait for moderation if you're not subscribed" rather than "you
need to be subscribed to post".

Marcin

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Re: Can recent i915 support more than 8192x8192 screen?

[Rodrigo Vivi]

On Tue, Jul 24, 2018 at 10:23:30PM +0200, Marcin Owsiany wrote:
>    2018-07-24 20:37 GMT+02:00 Rodrigo Vivi <[1]rodrigo.vivi@intel.com>:
> 
>      On Sat, Jul 21, 2018 at 09:43:53AM +0200, Marcin Owsiany wrote:
>      >    pt., 20 lip 2018, 23:35 użytkownik Rodrigo Vivi
>      >    <[1][2]rodrigo.vivi@intel.com> napisał:
>      >
>      >      On Fri, Jul 20, 2018 at 11:01:38PM +0200, Marcin Owsiany
>      wrote:
>      >      >    2018-07-20 22:22 GMT+02:00 Rodrigo Vivi
>      >      <[1][2][3]rodrigo.vivi@intel.com>:
>      >      >
>      >      >    On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany
>      wrote:
>      >      >    PS: Sorry for the initial double-post, I thought my
>      first email
>      >      was
>      >      >    blackholed
>      >      np... I approved it as soon as I saw it there.
>      >      list is open, but I have to filter the non-subscribed emails
>      because
>      >      of
>      >      so many spams...
>      >
>      >    I see, perhaps it might make sense to mention that the list is
>      >    moderated to
>      >    [3][4]https://01.org/community/participation-guidelines#list
>      >    Currently the policy makes it sound like messages from
>      non-subscribers
>      >    are doomed for good.
>      Well, we have this link on list's main page:
>      [5]https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>      So I'm not sure where you are suggesting us to add this link.
> 
>    I'm not suggesting to add this link (I know it's there, that's how I
>    found it in the first place).
>    I'm suggesting to change the contents
>    of [6]https://01.org/community/participation-guidelines#list to say
>    "your posts will need to wait for moderation if you're not subscribed"
>    rather than "you need to be subscribed to post".

Oh I see.

These 01.org guidelines are a meta for 01.org related projects, not just
for graphics.

And I just noticed their "rules" state for subscribers only. What it
is not our case. Ours is public, but moderated to avoid spams.

Maybe it would be better to create our own description instead of having
this link there.

>    Marcin
> 
> References
> 
>    1. mailto:rodrigo.vivi@intel.com
>    2. mailto:rodrigo.vivi@intel.com
>    3. mailto:rodrigo.vivi@intel.com
>    4. https://01.org/community/participation-guidelines#list
>    5. https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>    6. https://01.org/community/participation-guidelines#list
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Re: Can recent i915 support more than 8192x8192 screen?

[Chris Wilson]

Quoting Rodrigo Vivi (2018-07-20 21:22:25)
> On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
> >    Hello,
> >    TL;DR: how can I set a 8960x2880 screen (not display) size on a T580? A
> >    patch for i915 that I found on the internets does not seem to work.
> >    Full story:
> >    I'm a rather happy user of ThinkPad T580 which comes with a
> >    high-density 3840x2160 LCD, and the following graphics hardware.
> >    00:02.0 VGA compatible controller: Intel Corporation Device 5917 (rev
> >    07) (prog-if 00 [VGA controller])
> >            Subsystem: Lenovo Device 225a
> >            Flags: bus master, fast devsel, latency 0, IRQ 142
> >            Memory at e7000000 (64-bit, non-prefetchable) [size=16M]
> >            Memory at c0000000 (64-bit, prefetchable) [size=256M]
> >            I/O ports at e000 [size=64]
> >            [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
> >            Capabilities: [40] Vendor Specific Information: Len=0c <?>
> >            Capabilities: [70] Express Root Complex Integrated Endpoint,
> >    MSI 00
> >            Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
> >            Capabilities: [d0] Power Management version 2
> >            Capabilities: [100] Process Address Space ID (PASID)
> >            Capabilities: [200] Address Translation Service (ATS)
> >            Capabilities: [300] Page Request Interface (PRI)
> >            Kernel driver in use: i915
> >            Kernel modules: i915
> >    Unfortunately attaching it to an external normal-density 2560x1440
> >    display means I need to apply scaling. Combined with the side-by-side
> >    arrangement of monitors, this means I'd need to set screen size
> >    to 8960x2880. However this does not work:
> >     $ xrandr --fb 8960x2880
> >     xrandr: screen cannot be larger than 8192x8192 (desired size
> >    8960x2880)
> >    I found this [1]thread on reddit about the same problem, where a user
> >    posted a simple patch claimed to be supplied by someone on #intel-gfx.
> >    Unfortunately it does not work (or at least is not sufficient) - after
> >    applying it xrandr does claim that 16384x16384 is possible, but
> >    actually trying to use more than 8192x8192 fails with an error
> >    (unfortunately I lost the exact message).
> 
> I'm afraid that it is a hardware limitation that you won't be able to
> workaround. But a log would be interesting anyway... (both dmesg and xorg.0.log)

It is only a hardware limitation for a single pipe. We have supported
32kx32k screens for over 6 years in SNA.
-Chris
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Re: Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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sob., 21 lip 2018, 10:20 użytkownik Chris Wilson <chris@chris-wilson.co.uk>
napisał:

> Quoting Rodrigo Vivi (2018-07-20 21:22:25)
> > On Thu, Jul 19, 2018 at 11:31:19PM +0200, Marcin Owsiany wrote:
> > >    Hello,
> > >    TL;DR: how can I set a 8960x2880 screen (not display) size on a
> T580? A
> > >    patch for i915 that I found on the internets does not seem to work.
> > >    Full story:
> > >    I'm a rather happy user of ThinkPad T580 which comes with a
> > >    high-density 3840x2160 LCD, and the following graphics hardware.
> > >    00:02.0 VGA compatible controller: Intel Corporation Device 5917
> (rev
> > >    07) (prog-if 00 [VGA controller])
> > >            Subsystem: Lenovo Device 225a
> > >            Flags: bus master, fast devsel, latency 0, IRQ 142
> > >            Memory at e7000000 (64-bit, non-prefetchable) [size=16M]
> > >            Memory at c0000000 (64-bit, prefetchable) [size=256M]
> > >            I/O ports at e000 [size=64]
> > >            [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
> > >            Capabilities: [40] Vendor Specific Information: Len=0c <?>
> > >            Capabilities: [70] Express Root Complex Integrated Endpoint,
> > >    MSI 00
> > >            Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
> > >            Capabilities: [d0] Power Management version 2
> > >            Capabilities: [100] Process Address Space ID (PASID)
> > >            Capabilities: [200] Address Translation Service (ATS)
> > >            Capabilities: [300] Page Request Interface (PRI)
> > >            Kernel driver in use: i915
> > >            Kernel modules: i915
> > >    Unfortunately attaching it to an external normal-density 2560x1440
> > >    display means I need to apply scaling. Combined with the
> side-by-side
> > >    arrangement of monitors, this means I'd need to set screen size
> > >    to 8960x2880. However this does not work:
> > >     $ xrandr --fb 8960x2880
> > >     xrandr: screen cannot be larger than 8192x8192 (desired size
> > >    8960x2880)
> > >    I found this [1]thread on reddit about the same problem, where a
> user
> > >    posted a simple patch claimed to be supplied by someone on
> #intel-gfx.
> > >    Unfortunately it does not work (or at least is not sufficient) -
> after
> > >    applying it xrandr does claim that 16384x16384 is possible, but
> > >    actually trying to use more than 8192x8192 fails with an error
> > >    (unfortunately I lost the exact message).
> >
> > I'm afraid that it is a hardware limitation that you won't be able to
> > workaround. But a log would be interesting anyway... (both dmesg and
> xorg.0.log)
>
> It is only a hardware limitation for a single pipe. We have supported
> 32kx32k screens for over 6 years in SNA.
>

Do you mean hardware, out Linux X? Does it mean it should be working
already on Linux 4.9.x (x~80)? Or does it depend on Ville's patch set?

Marcin

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Re: Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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sob., 21 lip 2018, 11:20 użytkownik Marcin Owsiany <marcin@owsiany.pl>
napisał:

>
> Do you mean hardware, out Linux X?
>

Do you mean hardware, *or Linux/X*?

Marcin

>

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Can recent i915 support more than 8192x8192 screen?

[Marcin Owsiany]

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Hello,

*TL;DR*: how can I set a 8960x2880 screen (not display) size on a T580? A
patch for i915 that I found on the internets does not seem to work.

Full story:

I'm a rather happy user of ThinkPad T580 which comes with a
high-density 3840x2160 LCD, and the following graphics hardware.

00:02.0 VGA compatible controller: Intel Corporation Device 5917 (rev 07)
(prog-if 00 [VGA controller])
        Subsystem: Lenovo Device 225a
        Flags: bus master, fast devsel, latency 0, IRQ 142
        Memory at e7000000 (64-bit, non-prefetchable) [size=16M]
        Memory at c0000000 (64-bit, prefetchable) [size=256M]
        I/O ports at e000 [size=64]
        [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
        Capabilities: [40] Vendor Specific Information: Len=0c <?>
        Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00
        Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Capabilities: [d0] Power Management version 2
        Capabilities: [100] Process Address Space ID (PASID)
        Capabilities: [200] Address Translation Service (ATS)
        Capabilities: [300] Page Request Interface (PRI)
        Kernel driver in use: i915
        Kernel modules: i915

Unfortunately attaching it to an external normal-density 2560x1440 display
means I need to apply scaling. Combined with the side-by-side arrangement
of monitors, this means I'd need to set screen size to 8960x2880. However
this does not work:

 $ xrandr --fb 8960x2880
 xrandr: screen cannot be larger than 8192x8192 (desired size 8960x2880)


I found this thread on reddit
<https://www.reddit.com/r/linux/comments/6bghzm/increasing_maximum_xorg_virtual_screen_resolution/>
 about the same problem, where a user posted a simple patch claimed to be
supplied by someone on #intel-gfx. Unfortunately it does not work (or at
least is not sufficient) - after applying it xrandr does claim
that 16384x16384 is possible, but actually trying to use more
than 8192x8192 fails with an error (unfortunately I lost the exact message).

My current workaround is to pretend that the displays are arranged
vertically, but even after a few months I'm sometimes having trouble
remembering that I need to move mouse cursor UP when I want to go to LEFT
display :-)

I wonder if someone could help me here. Even just getting a definite answer
on whether my hardware can in theory support this or not would be helpful,
since I found conflicting information.

FWIW I'm on Debian stable, Linux 4.9.8x.

regards,
Marcin

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