drm: bridge/dw_hdmi: adjust n/cts setting order

Patch derived from one from Yakir Yang.  Yakir Yang says:
For Designerware HDMI, the following write sequence is recommended:
1. aud_n3 (set bit ncts_atomic_write if desired)
2. aud_cts3 (set CTS_manual and CTS value if desired/enabled)
3. aud_cts2 (required in CTS_manual)
4. aud_cts1 (required in CTS_manual)
5. aud_n3 (bit ncts_atomic_write with same value as in step 1.)
6. aud_n2
7. aud_n1

However, avoid the ncts_atomic_write_bit and CTS_manual settings in this
patch, both of which are marked reserved in the iMX6 documentation.  All
iMX6 code in the wild seems to want CTS_manual cleared.

Having requested clarification from FSL, it appears that neither of
these bits are implemented in their version of the IP.
Acked-by: NPhilipp Zabel <p.zabel@pengutronix.de>
Tested-by: NPhilipp Zabel <p.zabel@pengutronix.de>
Acked-by: NAndy Yan <andy.yan@rock-chips.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

drivers/gpu/drm/bridge/dw_hdmi.c

@@ -182,20 +182,20 @@ static void hdmi_mask_writeb(struct dw_hdmi *hdmi, u8 data, unsigned int reg,
 static void hdmi_set_cts_n(struct dw_hdmi *hdmi, unsigned int cts,
 			   unsigned int n)
 {
-	hdmi_writeb(hdmi, n & 0xff, HDMI_AUD_N1);
-	hdmi_writeb(hdmi, (n >> 8) & 0xff, HDMI_AUD_N2);
-	hdmi_writeb(hdmi, (n >> 16) & 0x0f, HDMI_AUD_N3);
+	/* Must be set/cleared first */
+	hdmi_modb(hdmi, 0, HDMI_AUD_CTS3_CTS_MANUAL, HDMI_AUD_CTS3);
 
 	/* nshift factor = 0 */
 	hdmi_modb(hdmi, 0, HDMI_AUD_CTS3_N_SHIFT_MASK, HDMI_AUD_CTS3);
 
-	/* Must be set/cleared first */
-	hdmi_modb(hdmi, 0, HDMI_AUD_CTS3_CTS_MANUAL, HDMI_AUD_CTS3);
-
-	hdmi_writeb(hdmi, cts & 0xff, HDMI_AUD_CTS1);
-	hdmi_writeb(hdmi, (cts >> 8) & 0xff, HDMI_AUD_CTS2);
 	hdmi_writeb(hdmi, ((cts >> 16) & HDMI_AUD_CTS3_AUDCTS19_16_MASK) |
 		    HDMI_AUD_CTS3_CTS_MANUAL, HDMI_AUD_CTS3);
+	hdmi_writeb(hdmi, (cts >> 8) & 0xff, HDMI_AUD_CTS2);
+	hdmi_writeb(hdmi, cts & 0xff, HDMI_AUD_CTS1);
+
+	hdmi_writeb(hdmi, (n >> 16) & 0x0f, HDMI_AUD_N3);
+	hdmi_writeb(hdmi, (n >> 8) & 0xff, HDMI_AUD_N2);
+	hdmi_writeb(hdmi, n & 0xff, HDMI_AUD_N1);
 }
 
 static unsigned int hdmi_compute_n(unsigned int freq, unsigned long pixel_clk,