add mode_valid function, we can make sure the resolution is valid.

Signed-off-by: Tian Tao <tiantao6@hisilicon.com>
Signed-off-by: Gong junjie <gongjunjie2@huawei.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

---
v2:     declare hibmc_crtc_mode_valid as static.
        Modify the return value of hibmc_crtc_mode_valid .
---
 drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_de.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_de.c b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_de.c
index 843d784..675d629 100644
--- a/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_de.c
+++ b/drivers/gpu/drm/hisilicon/hibmc/hibmc_drm_de.c
@@ -242,6 +242,24 @@ static void hibmc_crtc_atomic_disable(struct drm_crtc *crtc,
        hibmc_set_current_gate(priv, reg);
 }

+static enum drm_mode_status hibmc_crtc_mode_valid(struct drm_crtc *crtc,
+                                       const struct drm_display_mode *mode)
+{
+       int i = 0;
+       int vrefresh = drm_mode_vrefresh(mode);
+
+       if (vrefresh < 59 || vrefresh > 61)
+               return MODE_NOCLOCK;
+
+       for (i = 0; i < ARRAY_SIZE(hibmc_pll_table); i++) {
+               if (hibmc_pll_table[i].hdisplay == mode->hdisplay &&
+                       hibmc_pll_table[i].vdisplay == mode->vdisplay)
+                       return MODE_OK;
+       }
+
+       return MODE_BAD;
+}
+
 static unsigned int format_pll_reg(void)
 {
        unsigned int pllreg = 0;
@@ -510,6 +528,7 @@ static const struct drm_crtc_helper_funcs hibmc_crtc_helper_funcs = {
        .atomic_flush   = hibmc_crtc_atomic_flush,
        .atomic_enable  = hibmc_crtc_atomic_enable,
        .atomic_disable = hibmc_crtc_atomic_disable,
+       .mode_valid = hibmc_crtc_mode_valid,
 };

 int hibmc_de_init(struct hibmc_drm_private *priv)
--
2.7.4