drm: arcpgu: Use crtc->mode_valid() callback

Now that we have a callback to check if crtc supports a given mode
we can use it in arcpgu so that we restrict the number of probbed
modes to the ones we can actually display.

This is specially useful because arcpgu crtc is responsible to set
a clock value in the commit() stage but unfortunatelly this clock
does not support all the needed ranges.

Also, remove the atomic_check() callback as mode_valid() callback
will be called before.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Reviewed-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Carlos Palminha <palminha@synopsys.com>
Cc: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Changes v4->v5:
	- Change commit message to "arcpgu" (Alexey)
Changes v3->v4:
	- Do not use aux function (Laurent)
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/c3bcd69016c77f68a03ff3cb6b22ca6f90e930b0.1495720737.git.joabreu@synopsys.com

drivers/gpu/drm/arc/arcpgu_crtc.c

@@ -64,6 +64,19 @@ static const struct drm_crtc_funcs arc_pgu_crtc_funcs = {
 	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
 };
 
+enum drm_mode_status arc_pgu_crtc_mode_valid(struct drm_crtc *crtc,
+					     const struct drm_display_mode *mode)
+{
+	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
+	long rate, clk_rate = mode->clock * 1000;
+
+	rate = clk_round_rate(arcpgu->clk, clk_rate);
+	if (rate != clk_rate)
+		return MODE_NOCLOCK;
+
+	return MODE_OK;
+}
+
 static void arc_pgu_crtc_mode_set_nofb(struct drm_crtc *crtc)
 {
 	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
@@ -129,20 +142,6 @@ static void arc_pgu_crtc_disable(struct drm_crtc *crtc)
 			      ~ARCPGU_CTRL_ENABLE_MASK);
 }
 
-static int arc_pgu_crtc_atomic_check(struct drm_crtc *crtc,
-				     struct drm_crtc_state *state)
-{
-	struct arcpgu_drm_private *arcpgu = crtc_to_arcpgu_priv(crtc);
-	struct drm_display_mode *mode = &state->adjusted_mode;
-	long rate, clk_rate = mode->clock * 1000;
-
-	rate = clk_round_rate(arcpgu->clk, clk_rate);
-	if (rate != clk_rate)
-		return -EINVAL;
-
-	return 0;
-}
-
 static void arc_pgu_crtc_atomic_begin(struct drm_crtc *crtc,
 				      struct drm_crtc_state *state)
 {
@@ -158,6 +157,7 @@ static void arc_pgu_crtc_atomic_begin(struct drm_crtc *crtc,
 }
 
 static const struct drm_crtc_helper_funcs arc_pgu_crtc_helper_funcs = {
+	.mode_valid	= arc_pgu_crtc_mode_valid,
 	.mode_set	= drm_helper_crtc_mode_set,
 	.mode_set_base	= drm_helper_crtc_mode_set_base,
 	.mode_set_nofb	= arc_pgu_crtc_mode_set_nofb,
@@ -165,7 +165,6 @@ static const struct drm_crtc_helper_funcs arc_pgu_crtc_helper_funcs = {
 	.disable	= arc_pgu_crtc_disable,
 	.prepare	= arc_pgu_crtc_disable,
 	.commit		= arc_pgu_crtc_enable,
-	.atomic_check	= arc_pgu_crtc_atomic_check,
 	.atomic_begin	= arc_pgu_crtc_atomic_begin,
 };