drm/vc4: hdmi: Move clock calculation into its own function

The code to compute our clock rate for a given setup will be called in
multiple places in the next patches, so let's create a separate function
for it.
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Acked-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220222164042.403112-4-maxime@cerno.tech

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -1258,6 +1258,38 @@ vc4_hdmi_encoder_clock_valid(const struct vc4_hdmi *vc4_hdmi,
 	return MODE_OK;
 }
 
+static unsigned long long
+vc4_hdmi_encoder_compute_mode_clock(const struct drm_display_mode *mode,
+				    unsigned int bpc)
+{
+	unsigned long long clock = mode->clock * 1000;
+
+	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
+		clock = clock * 2;
+
+	clock = clock * bpc;
+	do_div(clock, 8);
+
+	return clock;
+}
+
+static int
+vc4_hdmi_encoder_compute_clock(const struct vc4_hdmi *vc4_hdmi,
+			       struct vc4_hdmi_connector_state *vc4_state,
+			       const struct drm_display_mode *mode,
+			       unsigned int bpc)
+{
+	unsigned long long clock;
+
+	clock = vc4_hdmi_encoder_compute_mode_clock(mode, bpc);
+	if (vc4_hdmi_encoder_clock_valid(vc4_hdmi, clock) != MODE_OK)
+		return -EINVAL;
+
+	vc4_state->tmds_char_rate = clock;
+
+	return 0;
+}
+
 #define WIFI_2_4GHz_CH1_MIN_FREQ	2400000000ULL
 #define WIFI_2_4GHz_CH1_MAX_FREQ	2422000000ULL
 
@@ -1270,6 +1302,7 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder,
 	struct vc4_hdmi *vc4_hdmi = encoder_to_vc4_hdmi(encoder);
 	unsigned long long tmds_char_rate = mode->clock * 1000;
 	unsigned long long tmds_bit_rate;
+	int ret;
 
 	if (vc4_hdmi->variant->unsupported_odd_h_timings &&
 	    ((mode->hdisplay % 2) || (mode->hsync_start % 2) ||
@@ -1290,21 +1323,10 @@ static int vc4_hdmi_encoder_atomic_check(struct drm_encoder *encoder,
 		tmds_char_rate = mode->clock * 1000;
 	}
 
-	if (conn_state->max_bpc == 12) {
-		tmds_char_rate = tmds_char_rate * 150;
-		do_div(tmds_char_rate, 100);
-	} else if (conn_state->max_bpc == 10) {
-		tmds_char_rate = tmds_char_rate * 125;
-		do_div(tmds_char_rate, 100);
-	}
-
-	if (mode->flags & DRM_MODE_FLAG_DBLCLK)
-		tmds_char_rate = tmds_char_rate * 2;
-
-	if (vc4_hdmi_encoder_clock_valid(vc4_hdmi, tmds_char_rate) != MODE_OK)
-		return -EINVAL;
-
-	vc4_state->tmds_char_rate = tmds_char_rate;
+	ret = vc4_hdmi_encoder_compute_clock(vc4_hdmi, vc4_state, mode,
+					     conn_state->max_bpc);
+	if (ret)
+		return ret;
 
 	return 0;
 }