drm/i2c: tda998x: adjust the audio clock divider for S/PDIF

According to some tests on the Cubox (Marvell Armada 510 + TDA19988),
the S/PDIF input asks for a greater audio clock divider.

Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

drivers/gpu/drm/i2c/tda998x_drv.c

@@ -680,10 +680,14 @@ tda998x_configure_audio(struct tda998x_priv *priv,
 	 * There is no detailed info in the datasheet, so we just
 	 * assume 100MHz requires larger divider.
 	 */
+	adiv = AUDIO_DIV_SERCLK_8;
 	if (mode->clock > 100000)
-		adiv = AUDIO_DIV_SERCLK_16;
-	else
-		adiv = AUDIO_DIV_SERCLK_8;
+		adiv++;			/* AUDIO_DIV_SERCLK_16 */
+
+	/* S/PDIF asks for a larger divider */
+	if (p->audio_format == AFMT_SPDIF)
+		adiv++;			/* AUDIO_DIV_SERCLK_16 or _32 */
+
 	reg_write(priv, REG_AUDIO_DIV, adiv);
 
 	/*