[PATCH] drm: tilcdc: Calculate the vrefresh if it is not set by userspace

[Kevin Hao]

The check for vrefresh has been removed by commit 11abbc9f39e0
("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is
enabled"). But the userspace is really possible to request a display
mode with vrefresh uninitialized, then it would cause the following
calltrace:
  [<c010fa20>] (unwind_backtrace) from [<c010c508>] (show_stack+0x20/0x24)
  [<c010c508>] (show_stack) from [<c0959744>] (dump_stack+0x20/0x28)
  [<c0959744>] (dump_stack) from [<c010c23c>] (__div0+0x20/0x28)
  [<c010c23c>] (__div0) from [<c095805c>] (Ldiv0+0x8/0x14)
  [<c095805c>] (Ldiv0) from [<c0615ccc>] (tilcdc_crtc_update_fb+0xa8/0x1d4)
  [<c0615ccc>] (tilcdc_crtc_update_fb) from [<c0614b70>] (tilcdc_plane_atomic_update+0x54/0x5c)
  [<c0614b70>] (tilcdc_plane_atomic_update) from [<c05c53a4>] (drm_atomic_helper_commit_planes+0x1b4/0x270)
  [<c05c53a4>] (drm_atomic_helper_commit_planes) from [<c0617d48>] (tilcdc_commit+0x58/0x84)
  [<c0617d48>] (tilcdc_commit) from [<c05e3f08>] (drm_atomic_commit+0x54/0x68)
  [<c05e3f08>] (drm_atomic_commit) from [<c05c937c>] (drm_atomic_helper_set_config+0x68/0x9c)
  [<c05c937c>] (drm_atomic_helper_set_config) from [<c05d843c>] (__drm_mode_set_config_internal+0x60/0xe0)
  [<c05d843c>] (__drm_mode_set_config_internal) from [<c05d906c>] (drm_mode_setcrtc+0x3a8/0x4c0)
  [<c05d906c>] (drm_mode_setcrtc) from [<c05d3c2c>] (drm_ioctl_kernel+0x78/0xb0)
  [<c05d3c2c>] (drm_ioctl_kernel) from [<c05d3e60>] (drm_ioctl+0x1fc/0x328)
  [<c05d3e60>] (drm_ioctl) from [<c0280008>] (vfs_ioctl+0x28/0x44)
  [<c0280008>] (vfs_ioctl) from [<c0280a00>] (do_vfs_ioctl+0x890/0x8ec)
  [<c0280a00>] (do_vfs_ioctl) from [<c0280abc>] (SyS_ioctl+0x60/0x7c)
  [<c0280abc>] (SyS_ioctl) from [<c01078e0>] (ret_fast_syscall+0x0/0x48)

So calculate the vrefresh in mode_fixup() to make sure there always
have a valid vrefresh.

Fixes: 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
Cc: <stable at vger.kernel.org> # v4.11+
Signed-off-by: Kevin Hao <kexin.hao at windriver.com>
---
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index d2589f310437..16b020a9044c 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -690,6 +690,9 @@ static bool tilcdc_crtc_mode_fixup(struct drm_crtc *crtc,
 		adjusted_mode->flags &= ~DRM_MODE_FLAG_PHSYNC;
 	}
 
+	if (!adjusted_mode->vrefresh)
+		adjusted_mode->vrefresh = drm_mode_vrefresh(adjusted_mode);
+
 	return true;
 }
 
-- 
2.9.3