drm/tegra: sor - Do not hardcode number of blank symbols

The number of HBLANK and VBLANK symbols can be computed at runtime so
that they can be set appropriately depending on the video mode and DP
link.

These values are used by the packet generation logic to determine how
many audio samples can be transferred during the blanking intervals.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/gpu/drm/tegra/sor.c

@@ -48,6 +48,9 @@ struct tegra_sor_config {
 	u32 tu_size;
 	u32 active_frac;
 	u32 watermark;
+
+	u32 hblank_symbols;
+	u32 vblank_symbols;
 };
 
 static inline struct tegra_sor *
@@ -393,8 +396,8 @@ static int tegra_sor_calc_config(struct tegra_sor *sor,
 {
 	const u64 f = 100000, link_rate = link->rate * 1000;
 	const u64 pclk = mode->clock * 1000;
+	u64 input, output, watermark, num;
 	struct tegra_sor_params params;
-	u64 input, output, watermark;
 	u32 num_syms_per_line;
 	unsigned int i;
 
@@ -458,6 +461,23 @@ static int tegra_sor_calc_config(struct tegra_sor *sor,
 			config->watermark);
 	}
 
+	/* compute the number of symbols per horizontal blanking interval */
+	num = ((mode->htotal - mode->hdisplay) - 7) * link_rate;
+	config->hblank_symbols = div_u64(num, pclk);
+
+	if (link->capabilities & DP_LINK_CAP_ENHANCED_FRAMING)
+		config->hblank_symbols -= 3;
+
+	config->hblank_symbols -= 12 / link->num_lanes;
+
+	/* compute the number of symbols per vertical blanking interval */
+	num = (mode->hdisplay - 25) * link_rate;
+	config->vblank_symbols = div_u64(num, pclk);
+	config->vblank_symbols -= 36 / link->num_lanes + 4;
+
+	dev_dbg(sor->dev, "blank symbols: H:%u V:%u\n", config->hblank_symbols,
+		config->vblank_symbols);
+
 	return 0;
 }
 
@@ -684,12 +704,12 @@ static int tegra_output_sor_enable(struct tegra_output *output)
 
 	value = tegra_sor_readl(sor, SOR_DP_AUDIO_HBLANK_SYMBOLS);
 	value &= ~SOR_DP_AUDIO_HBLANK_SYMBOLS_MASK;
-	value |= 137; /* XXX: don't hardcode? */
+	value |= config.hblank_symbols & 0xffff;
 	tegra_sor_writel(sor, value, SOR_DP_AUDIO_HBLANK_SYMBOLS);
 
 	value = tegra_sor_readl(sor, SOR_DP_AUDIO_VBLANK_SYMBOLS);
 	value &= ~SOR_DP_AUDIO_VBLANK_SYMBOLS_MASK;
-	value |= 2368; /* XXX: don't hardcode? */
+	value |= config.vblank_symbols & 0xffff;
 	tegra_sor_writel(sor, value, SOR_DP_AUDIO_VBLANK_SYMBOLS);
 
 	/* enable pad calibration logic */