drm/arm/hdlcd: Actually validate CRTC modes

Rather than allowing any old mode through, then subsequently refusing
unmatchable clock rates in atomic_check when it's too late to back out
and pick a different mode, let's do that validation up-front where it
will cause unsupported modes to be correctly pruned in the first place.

This also eliminates an issue whereby a perceived clock rate of 0 would
cause atomic disable to fail and prevent the module from being unloaded.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>

1 files changed, 5 insertions, 6 deletions

diff --git a/drivers/gpu/drm/arm/hdlcd_crtc.c b/drivers/gpu/drm/arm/hdlcd_crtc.c
index 0b2b62f8fa3c..ecac6fe0b213 100644
--- a/drivers/gpu/drm/arm/hdlcd_crtc.c
+++ b/drivers/gpu/drm/arm/hdlcd_crtc.c
@@ -186,20 +186,19 @@ static void hdlcd_crtc_atomic_disable(struct drm_crtc *crtc,
         clk_disable_unprepare(hdlcd->clk);
 }
 
-static int hdlcd_crtc_atomic_check(struct drm_crtc *crtc,
-                                   struct drm_crtc_state *state)
+static enum drm_mode_status hdlcd_crtc_mode_valid(struct drm_crtc *crtc,
+                const struct drm_display_mode *mode)
 {
         struct hdlcd_drm_private *hdlcd = crtc_to_hdlcd_priv(crtc);
-        struct drm_display_mode *mode = &state->adjusted_mode;
         long rate, clk_rate = mode->clock * 1000;
 
         rate = clk_round_rate(hdlcd->clk, clk_rate);
         if (rate != clk_rate) {
                 /* clock required by mode not supported by hardware */
-                return -EINVAL;
+                return MODE_NOCLOCK;
         }
 
-        return 0;
+        return MODE_OK;
 }
 
 static void hdlcd_crtc_atomic_begin(struct drm_crtc *crtc,
@@ -220,7 +219,7 @@ static void hdlcd_crtc_atomic_begin(struct drm_crtc *crtc,
 }
 
 static const struct drm_crtc_helper_funcs hdlcd_crtc_helper_funcs = {
-        .atomic_check   = hdlcd_crtc_atomic_check,
+        .mode_valid     = hdlcd_crtc_mode_valid,
         .atomic_begin   = hdlcd_crtc_atomic_begin,
         .atomic_enable  = hdlcd_crtc_atomic_enable,
         .atomic_disable = hdlcd_crtc_atomic_disable,