[Intel-gfx] 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