ASoC: Warn on low WM8994 AIFCLK

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>

sound/soc/codecs/wm8994.c

@@ -1769,6 +1769,11 @@ static int configure_aif_clock(struct snd_soc_codec *codec, int aif)
 		dev_dbg(codec->dev, "Dividing AIF%d clock to %dHz\n",
 			aif + 1, rate);
 	}
+
+	if (rate && rate < 3000000)
+		dev_warn(codec->dev, "AIF%dCLK is %dHz, should be >=3MHz for optimal performance\n",
+			 aif + 1, rate);
+
 	wm8994->aifclk[aif] = rate;
 
 	snd_soc_update_bits(codec, WM8994_AIF1_CLOCKING_1 + offset,