3 files changed, 14 insertions, 2 deletions
diff --git a/hw/xfree86/drivers/modesetting/driver.c b/hw/xfree86/drivers/modesetting/driver.c
index ec4189a2c..5dc8e202c 100644
--- a/hw/xfree86/drivers/modesetting/driver.c
+++ b/hw/xfree86/drivers/modesetting/driver.c
@@ -1040,6 +1040,14 @@ PreInit(ScrnInfoPtr pScrn, int flags)
 #endif
     }
 
+    /*
+     * Use "atomic modesetting disable" request to detect if the kms driver is
+     * atomic capable, regardless if we will actually use atomic modesetting.
+     * This is effectively a no-op, we only care about the return status code.
+     */
+    ret = drmSetClientCap(ms->fd, DRM_CLIENT_CAP_ATOMIC, 0);
+    ms->atomic_modeset_capable = (ret == 0);
+
     if (xf86ReturnOptValBool(ms->drmmode.Options, OPTION_ATOMIC, FALSE)) {
         ret = drmSetClientCap(ms->fd, DRM_CLIENT_CAP_ATOMIC, 1);
         ms->atomic_modeset = (ret == 0);
diff --git a/hw/xfree86/drivers/modesetting/driver.h b/hw/xfree86/drivers/modesetting/driver.h
index a99f37871..28810c063 100644
--- a/hw/xfree86/drivers/modesetting/driver.h
+++ b/hw/xfree86/drivers/modesetting/driver.h
@@ -108,6 +108,7 @@ typedef struct _modesettingRec {
      * Page flipping stuff.
      *  @{
      */
+    Bool atomic_modeset_capable;
     Bool atomic_modeset;
     Bool pending_modeset;
     /** @} */
diff --git a/hw/xfree86/drivers/modesetting/present.c b/hw/xfree86/drivers/modesetting/present.c
index 186309a29..f7a475356 100644
--- a/hw/xfree86/drivers/modesetting/present.c
+++ b/hw/xfree86/drivers/modesetting/present.c
@@ -252,8 +252,11 @@ ms_present_check_unflip(RRCrtcPtr crtc,
     if (num_crtcs_on == 0)
         return FALSE;
 
-    /* Check stride, can't change that on flip */
-    if (!ms->atomic_modeset &&
+    /*
+     * Check stride, can't change that reliably on flip on some drivers, unless
+     * the kms driver is atomic_modeset_capable.
+     */
+    if (!ms->atomic_modeset_capable &&
         pixmap->devKind != drmmode_bo_get_pitch(&ms->drmmode.front_bo))
         return FALSE;