RandR + i915 (HD 4600 / Haswell) -- Cannot switch from internal to 3x external

[Chris Wilson]

On Tue, Jun 16, 2015 at 10:40:17AM -0500, Nathan Schulte wrote:
> I am running Debian Sid on a laptop machine with an Intel Haswell
> CPU with Intel HD 4600 graphics.
> 
> >$ Xorg -version
> >
> >X.Org X Server 1.17.1
> >Release Date: 2015-02-10
> >X Protocol Version 11, Revision 0
> >Build Operating System: Linux 3.16.0-4-amd64 x86_64 Debian
> >Current Operating System: Linux desmas-l 4.0.0-1-amd64 #1 SMP Debian 4.0.2-1 (2015-05-11) x86_64
> >Kernel command line: BOOT_IMAGE=/vmlinuz-4.0.0-1-amd64 root=UUID=f5ba8b5c-63aa-4a67-a07c-dd8d3297b2d3 ro quiet
> >Build Date: 04 May 2015  11:22:06PM
> >xorg-server 2:1.17.1-2 (http://www.debian.org/support)
> >Current version of pixman: 0.32.6
> >	Before reporting problems, check http://wiki.x.org
> >	to make sure that you have the latest version.
> 
> When using RandR (xrandr, arandr), I am unable to re-configure my
> displays from the one integrated in the machine (eDP1), to three
> external displays (in this case, HDMI1 (DP -> DVI via DP++), HDMI2
> (HDMI -> DVI), HDMI3 (miniDP -> DVI); the machine has three external
> connectors).  I haven't played with DP and multi-stream transport,
> but I expect it would behave similarly (that is, annoyingly).
> 
> >xrandr: cannot find crtc for output HDMI
> 
> My work-around is to issue two RandR requests, with the first one
> enabling an external display, and the second one disabling the
> internal display and enabling the rest.  This is rather annoying and
> conflicts with some of the scripts I use to automatically configure
> my displays based upon context and hot-plug (autorandr).
> 
> The internal display is 1920x1080, and the three external displays
> are identical monitors with 1920x1200 resolution.  I believe this is
> key, and has to do with the number of available PLLs (2) and
> encoders (3) in the Intel hardware.
> 
> I've attached an strace (xrandr.log) of the xrandr command:
> 
> >xrandr \
> >    --output DP2 --off \
> >    --output DP1 --off \
> >    --output HDMI3 --mode 1920x1200 --pos 3120x0 --rotate left \
> >    --output HDMI2 --mode 1920x1200 --pos 1920x0 --rotate left \
> >    --output HDMI1 --primary --mode 1920x1200 --pos 0x410 --rotate normal \
> >    --output eDP1 --off \
> >    --output VGA1 --off
> 
> Any help resolving this issue is greatly appreciated.

I think this is the right fix:

diff --git a/xrandr.c b/xrandr.c
index fbfd93e..c0feac3 100644
--- a/xrandr.c
+++ b/xrandr.c
@@ -3029,7 +3029,7 @@ main (int argc, char **argv)
            if (!config_output) argerr ("%s must be used after --output\n", argv[i]);
            set_name_xid (&config_output->mode, None);
            set_name_xid (&config_output->crtc, None);
-           config_output->changes |= changes_mode;
+           config_output->changes |= changes_mode | changes_crtc;
            continue;
        }
        if (!strcmp ("--fb", argv[i])) {

-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre