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From 68854b3c7771ad5754ad46d42f45f626ca87b4ac Mon Sep 17 00:00:00 2001
From: Neil Armstrong <narmstrong@baylibre.com>
Date: Mon, 2 Jul 2018 12:21:55 +0200
Subject: [PATCH] drm: bridge: dw-hdmi: Use AUTO CTS setup mode when non-AHB
 audio

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 41 ++++++++++++++++++++-----------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 5971976..1fc1270 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -430,8 +430,12 @@ static void hdmi_set_cts_n(struct dw_hdmi *hdmi, unsigned int cts,
 	/* nshift factor = 0 */
 	hdmi_modb(hdmi, 0, HDMI_AUD_CTS3_N_SHIFT_MASK, HDMI_AUD_CTS3);
 
-	hdmi_writeb(hdmi, ((cts >> 16) & HDMI_AUD_CTS3_AUDCTS19_16_MASK) |
-		    HDMI_AUD_CTS3_CTS_MANUAL, HDMI_AUD_CTS3);
+	/* Use Auto CTS mode with CTS is unknown */
+	if (cts)
+		hdmi_writeb(hdmi, ((cts >> 16) & HDMI_AUD_CTS3_AUDCTS19_16_MASK) |
+			    HDMI_AUD_CTS3_CTS_MANUAL, HDMI_AUD_CTS3);
+	else
+		hdmi_writeb(hdmi, 0, HDMI_AUD_CTS3);
 	hdmi_writeb(hdmi, (cts >> 8) & 0xff, HDMI_AUD_CTS2);
 	hdmi_writeb(hdmi, cts & 0xff, HDMI_AUD_CTS1);
 
@@ -501,24 +505,31 @@ static void hdmi_set_clk_regenerator(struct dw_hdmi *hdmi,
 {
 	unsigned long ftdms = pixel_clk;
 	unsigned int n, cts;
+	u8 config3;
 	u64 tmp;
 
 	n = hdmi_compute_n(sample_rate, pixel_clk);
 
-	/*
-	 * Compute the CTS value from the N value.  Note that CTS and N
-	 * can be up to 20 bits in total, so we need 64-bit math.  Also
-	 * note that our TDMS clock is not fully accurate; it is accurate
-	 * to kHz.  This can introduce an unnecessary remainder in the
-	 * calculation below, so we don't try to warn about that.
-	 */
-	tmp = (u64)ftdms * n;
-	do_div(tmp, 128 * sample_rate);
-	cts = tmp;
+	config3 = hdmi_readb(hdmi, HDMI_CONFIG3_ID);
 
-	dev_dbg(hdmi->dev, "%s: fs=%uHz ftdms=%lu.%03luMHz N=%d cts=%d\n",
-		__func__, sample_rate, ftdms / 1000000, (ftdms / 1000) % 1000,
-		n, cts);
+	if (config3 & HDMI_CONFIG3_AHBAUDDMA) {
+		/*
+		 * Compute the CTS value from the N value.  Note that CTS and N
+		 * can be up to 20 bits in total, so we need 64-bit math.  Also
+		 * note that our TDMS clock is not fully accurate; it is
+		 * accurate to kHz.  This can introduce an unnecessary remainder
+		 * in the calculation below, so we don't try to warn about that.
+		 */
+		tmp = (u64)ftdms * n;
+		do_div(tmp, 128 * sample_rate);
+		cts = tmp;
+
+		dev_dbg(hdmi->dev, "%s: fs=%uHz ftdms=%lu.%03luMHz N=%d cts=%d\n",
+			__func__, sample_rate,
+			ftdms / 1000000, (ftdms / 1000) % 1000,
+			n, cts);
+	} else
+		cts = 0;
 
 	spin_lock_irq(&hdmi->audio_lock);
 	hdmi->audio_n = n;