[PATCH xserver] modesetting: Also disable CRTC in drmmode_output_disable()

[Dave Airlie]

On 8 June 2018 at 10:30, Lyude Paul <lyude at redhat.com> wrote:
> So, this did actually work on older kernels at one point in time,
> however it seems that this working was a result of some of the Linux
> kernel's atomic modesetting helpers not preserving the CRTC's enabled
> state in the right spots. This was fixed in:
>
> 846c7dfc1193 ("drm/atomic: Try to preserve the crtc enabled state in drm_atomic_remove_fb, v2")
>
> As a result, atomic commits which simply disassociate a DRM connector
> with it's CRTC while leaving the CRTC in an enabled state aren't enough
> to disable the CRTC, and result in the atomic commit failing. This
> currently can cause issues with MST hotplugging where X will end up
> failing to disable the MST outputs after they've left the system. A
> simple reproducer:
>
> - Start up Xorg
> - Connect an MST hub with displays connected to it
> - Remove the hub
> - Now there should be CRTCs stuck on the orphaned MST connectors, and X
>   won't be able to reclaim them.
>
> Signed-off-by: Lyude Paul <lyude at redhat.com>
> Cc: Louis-Francis Ratté-Boulianne <lfrb at collabora.com>

Reviewed-by: Dave Airlie <airlied at redhat.com>

> ---
>  hw/xfree86/drivers/modesetting/drmmode_display.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/hw/xfree86/drivers/modesetting/drmmode_display.c b/hw/xfree86/drivers/modesetting/drmmode_display.c
> index 859a21a9d..375be4234 100644
> --- a/hw/xfree86/drivers/modesetting/drmmode_display.c
> +++ b/hw/xfree86/drivers/modesetting/drmmode_display.c
> @@ -695,18 +695,21 @@ drmmode_output_disable(xf86OutputPtr output)
>  {
>      modesettingPtr ms = modesettingPTR(output->scrn);
>      drmmode_output_private_ptr drmmode_output = output->driver_private;
> +    xf86CrtcPtr crtc = drmmode_output->current_crtc;
>      drmModeAtomicReq *req = drmModeAtomicAlloc();
>      uint32_t flags = DRM_MODE_ATOMIC_ALLOW_MODESET;
> -    int ret;
> +    int ret = 0;
>
>      assert(ms->atomic_modeset);
>
>      if (!req)
>          return 1;
>
> -    /* XXX Can we disable all outputs without disabling CRTC right away? */
> -    ret = connector_add_prop(req, drmmode_output,
> -                             DRMMODE_CONNECTOR_CRTC_ID, 0);
> +    ret |= connector_add_prop(req, drmmode_output,
> +                              DRMMODE_CONNECTOR_CRTC_ID, 0);
> +    if (crtc)
> +        ret |= crtc_add_dpms_props(req, crtc, DPMSModeOff, NULL);
> +
>      if (ret == 0)
>          ret = drmModeAtomicCommit(ms->fd, req, flags, NULL);
>
> --
> 2.17.1
>
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