We are using the vrefresh to check if we are too close to vertical
sync to update the two framebuffer DMA registers and risk a
collision. The vrefresh is coming from user space and normally it is
not used for anything. For instance xserver leaves vrefresh to zero
causing a division by zero when setting the mode. We want to make sure
the value is valid and force its recalculation in
tilcdc_crtc_set_mode().
Reported-by: Kevin Hao <kexin.hao@xxxxxxxxxxxxx>
Fixes: 11abbc9f39e0 ("drm/tilcdc: Set framebuffer DMA address to HW only if CRTC is enabled")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
Signed-off-by: Jyri Sarha <jsarha@xxxxxx>
---
drivers/gpu/drm/tilcdc/tilcdc_crtc.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index 704db24..aa5e87c 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -459,6 +459,16 @@ static void tilcdc_crtc_set_mode(struct drm_crtc *crtc)
drm_framebuffer_get(fb);
crtc->hwmode = crtc->state->adjusted_mode;
+
+ /* We are using the vrefresh to check if we are too close to
+ * vertical sync to update the two framebuffer DMA registers
+ * and risk a collision. The vrefresh is coming from user
+ * space and normally it is not used for anything. We want to
+ * make sure the value is valid and force its recalculation
+ * here.
+ */
+ crtc->hwmode.vrefresh = 0;
+ crtc->hwmode.vrefresh = drm_mode_vrefresh(&crtc->hwmode);
}
static void tilcdc_crtc_enable(struct drm_crtc *crtc)
--
1.9.1
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