drm/bridge: dw-hdmi-i2s: reset audio fifo before applying new params

When changing the audio hw params, reset the audio fifo to make sure
any old remaining data is flushed.

The databook mentions that such reset should be followed by a reset of
the i2s block to make sure the samples stay aligned
Reviewed-by: NJonas Karlman <jonas@kwiboo.se>
Signed-off-by: NJerome Brunet <jbrunet@baylibre.com>
Reviewed-by: NNeil Armstrong <narmstrong@baylibre.com>
Signed-off-by: NNeil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190812120726.1528-7-jbrunet@baylibre.com

drivers/gpu/drm/bridge/synopsys/dw-hdmi-i2s-audio.c

@@ -49,6 +49,10 @@ static int dw_hdmi_i2s_hw_params(struct device *dev, void *data,
 		return -EINVAL;
 	}
 
+	/* Reset the FIFOs before applying new params */
+	hdmi_write(audio, HDMI_AUD_CONF0_SW_RESET, HDMI_AUD_CONF0);
+	hdmi_write(audio, (u8)~HDMI_MC_SWRSTZ_I2SSWRST_REQ, HDMI_MC_SWRSTZ);
+
 	inputclkfs	= HDMI_AUD_INPUTCLKFS_64FS;
 	conf0		= HDMI_AUD_CONF0_I2S_ALL_ENABLE;
 
@@ -102,8 +106,6 @@ static void dw_hdmi_i2s_audio_shutdown(struct device *dev, void *data)
 	struct dw_hdmi *hdmi = audio->hdmi;
 
 	dw_hdmi_audio_disable(hdmi);
-
-	hdmi_write(audio, HDMI_AUD_CONF0_SW_RESET, HDMI_AUD_CONF0);
 }
 
 static int dw_hdmi_i2s_get_dai_id(struct snd_soc_component *component,

drivers/gpu/drm/bridge/synopsys/dw-hdmi.h

@@ -940,6 +940,7 @@ enum {
 	HDMI_MC_CLKDIS_PIXELCLK_DISABLE = 0x1,
 
 /* MC_SWRSTZ field values */
+	HDMI_MC_SWRSTZ_I2SSWRST_REQ = 0x08,
 	HDMI_MC_SWRSTZ_TMDSSWRST_REQ = 0x02,
 
 /* MC_FLOWCTRL field values */