drm/vc4: hdmi: Block odd horizontal timings

The FIFO between the pixelvalve and the HDMI controller runs at 2 pixels
per clock cycle, and cannot deal with odd timings.

Let's reject any mode with such timings.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201029122522.1917579-2-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -768,6 +768,11 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder,
 	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
 	unsigned long long pixel_rate = mode->clock * 1000;
 
+	if (vc4_hdmi->variant->unsupported_odd_h_timings &&
+	    ((mode->hdisplay % 2) || (mode->hsync_start % 2) ||
+	     (mode->hsync_end % 2) || (mode->htotal % 2)))
+		return -EINVAL;
+
 	if (pixel_rate > vc4_hdmi->variant->max_pixel_clock)
 		return -EINVAL;
 
@@ -780,6 +785,11 @@ vc4_hdmi_encoder_mode_valid(struct drm_encoder *encoder,
 {
 	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
 
+	if (vc4_hdmi->variant->unsupported_odd_h_timings &&
+	    ((mode->hdisplay % 2) || (mode->hsync_start % 2) ||
+	     (mode->hsync_end % 2) || (mode->htotal % 2)))
+		return MODE_H_ILLEGAL;
+
 	if ((mode->clock * 1000) > vc4_hdmi->variant->max_pixel_clock)
 		return MODE_CLOCK_HIGH;
 
@@ -1832,6 +1842,7 @@ static const struct vc4_hdmi_variant bcm2711_hdmi0_variant = {
 		PHY_LANE_2,
 		PHY_LANE_CK,
 	},
+	.unsupported_odd_h_timings	= true,
 
 	.init_resources		= vc5_hdmi_init_resources,
 	.csc_setup		= vc5_hdmi_csc_setup,
@@ -1857,6 +1868,7 @@ static const struct vc4_hdmi_variant bcm2711_hdmi1_variant = {
 		PHY_LANE_CK,
 		PHY_LANE_2,
 	},
+	.unsupported_odd_h_timings	= true,
 
 	.init_resources		= vc5_hdmi_init_resources,
 	.csc_setup		= vc5_hdmi_csc_setup,

drivers/gpu/drm/vc4/vc4_hdmi.h

@@ -62,6 +62,9 @@ struct vc4_hdmi_variant {
 	 */
 	enum vc4_hdmi_phy_channel phy_lane_mapping[4];
 
+	/* The BCM2711 cannot deal with odd horizontal pixel timings */
+	bool unsupported_odd_h_timings;
+
 	/* Callback to get the resources (memory region, interrupts,
 	 * clocks, etc) for that variant.
 	 */