ASoC: SOF: Intel: cnl-ipc: read all IPC registers first

Align with hardware recommended sequences, and read all IPC registers
before doing any other actions. Playing with BUSY and DONE bits may
invalidate values.

The values read may not actually be necessary but at least this
provides a snapshot of the IPC registers with no consistency issues.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/cnl.c

@@ -42,6 +42,8 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 	hipcida = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCIDA);
 	hipcctl = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCCTL);
 	hipctdr = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCTDR);
+	hipctdd = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCTDD);
+	hipci = snd_sof_dsp_read(sdev, HDA_DSP_BAR, CNL_DSP_REG_HIPCIDR);
 
 	/* reenable IPC interrupt */
 	snd_sof_dsp_update_bits(sdev, HDA_DSP_BAR, HDA_DSP_REG_ADSPIC,
@@ -50,8 +52,6 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 	/* reply message from DSP */
 	if (hipcida & CNL_DSP_REG_HIPCIDA_DONE &&
 	    hipcctl & CNL_DSP_REG_HIPCCTL_DONE) {
-		hipci = snd_sof_dsp_read(sdev, HDA_DSP_BAR,
-					 CNL_DSP_REG_HIPCIDR);
 		msg_ext = hipci & CNL_DSP_REG_HIPCIDR_MSG_MASK;
 		msg = hipcida & CNL_DSP_REG_HIPCIDA_MSG_MASK;
 
@@ -84,8 +84,6 @@ static irqreturn_t cnl_ipc_irq_thread(int irq, void *context)
 
 	/* new message from DSP */
 	if (hipctdr & CNL_DSP_REG_HIPCTDR_BUSY) {
-		hipctdd = snd_sof_dsp_read(sdev, HDA_DSP_BAR,
-					   CNL_DSP_REG_HIPCTDD);
 		msg = hipctdr & CNL_DSP_REG_HIPCTDR_MSG_MASK;
 		msg_ext = hipctdd & CNL_DSP_REG_HIPCTDD_MSG_MASK;